38K on 2005 Caddy STS with the Northstar. I just can't seem to get rid of the cold piston rap. So I used 2 bottles of autorx in the 8qt. sump with castrol gtx 5-30. I also plan to do the same on the jag x-type with 68K on it. ( But nothing is wrong with that one ) It also has a large 7QT sump. I will let you know if I notice any change. Already have 200 miles on it.
2 In the stink ! AutoRX that is.
- Thread starter porkfarm
- Start date
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What kind of rinse our you doing ? this is the most important part of the application. Suggest you e-mail Gay Allan and Barkerman
and make your choice.
and make your choice.
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I don't think your piston slap will go away from using Auto-RX. It can cure a lot of things but unless it can change the clearances of the internals of your engine's hard parts the piston slap is there to stay.
ARX looks like good stuff and I am going to buy some for a couple of vehicles, but I don't think it can fix everything.
If it can, where can I buy stock?
ARX looks like good stuff and I am going to buy some for a couple of vehicles, but I don't think it can fix everything.
If it can, where can I buy stock?
It sure can't fix piston slap. Why would you think that?
COLD piston knock, slap whatever you want to call it. It is due to carbon on the piston tops and rings getting crudded up. ( as I understand it ) Only does it for about 2 mins. after a cold cold start up. It's a Nstar thing. I beat the boogie bag off it to keep it clean, and get the rings cleaned up, but I bought it used with 25K on it. I think it was lugged around. I cleaned the intake the best I could and even did the seafoam route, seems to have helped a lil bit, but did not get rid of it. I could always take it to stealership and have them do the TOC treatment, but I am hoping that this will help. It could be due to the new oil, but it seems better already. I did use a maint. dose of Auto RX last oil change. I plan on using Cat gtx for the rinse. Then might try M1 after that. The PenPlat was nothing great as far as sounds go.
The wife ran a 1998 Northstar for a number of years. Never experienced any piston slap but did have some oil burning issues. I believe they had some poorly designed ring packs back then. An ARX cleaning and subsequent mainenance dose seemed to help out the oil consumption issue some.
Ok. Maybe I should have said COLD Carbon RAP. CCR.. Like the band.
It keeps the carbon cleaned out of the combustion chamber. This is maybe a little more important with the Northstar than some other engines due to the tight squish volumes between the piston and the cylinder head. It's designed this way to promote good in-cylinder mixture motion (good combustion) but it has the down side of providing a ready place for carbon build-up to touch the piston - causing noise. Ever heard of the Northstar "cold carbon rap" problem?? Simply put you'll hear a rythmic, piston slap-like noise when the engine is cold. Very prominent and very annoying. Cause: excessive carbon build up causing the the piston to contact the carbon on the head - causing it to rock in the bore and "slap" Much more evident when the engine is cold and the pistons haven't expanded to full diameter yet. Simplest and easiest "fix" for this: A few good WOT (wide open throttle) accelerations to clear the carbon out. That is all it takes to eliminate the problem and prevent it from re-occurring.
It keeps the carbon cleaned out of the combustion chamber. This is maybe a little more important with the Northstar than some other engines due to the tight squish volumes between the piston and the cylinder head. It's designed this way to promote good in-cylinder mixture motion (good combustion) but it has the down side of providing a ready place for carbon build-up to touch the piston - causing noise. Ever heard of the Northstar "cold carbon rap" problem?? Simply put you'll hear a rythmic, piston slap-like noise when the engine is cold. Very prominent and very annoying. Cause: excessive carbon build up causing the the piston to contact the carbon on the head - causing it to rock in the bore and "slap" Much more evident when the engine is cold and the pistons haven't expanded to full diameter yet. Simplest and easiest "fix" for this: A few good WOT (wide open throttle) accelerations to clear the carbon out. That is all it takes to eliminate the problem and prevent it from re-occurring.
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Northstars tended to carbon up due to how they were driven, if you take it to a GM dealership with that problem they will basically just Seafoam it and change the oil.
Cold knocking sounds strange to me, because when the engine is hot, the higher compression will cause knocking if there is a lot of carbon in the top end but the rings won't make sound. If it goes away once the engine warms up, it's just piston slap. If it was from carbon, the knock would get worse the hotter it got.
If you had noise from the lash adjusters the ARX will help, and if it is that carboned up, ARX will help your rings and take other stuff out of the engine, but it won't get into the upper cylinder where the carbon would be to cause knocking/pinging.
There might be some fuel additives that could help with that issue to break down the carbon in the cylinder, but ARX generally can't help anything north of the rings other than cleaning up the oil return drains in your cylinder head, cleaning up the moving parts, and the lash adjusters.
Does premium/super premium fuel reduce it? For example, if your car takes 91, using 94?
GM makes an aerosol version of SeaFoam so you can spray it in through a vaccuum line and face as much risk of hydrolocking it. You'd probably foul your plugs and I would not do that without changing your oil right away.
I think ARX will help you but not with the issue of carbon on top of your pistons/in the combustion chamber, or piston slap.
Cold knocking sounds strange to me, because when the engine is hot, the higher compression will cause knocking if there is a lot of carbon in the top end but the rings won't make sound. If it goes away once the engine warms up, it's just piston slap. If it was from carbon, the knock would get worse the hotter it got.
If you had noise from the lash adjusters the ARX will help, and if it is that carboned up, ARX will help your rings and take other stuff out of the engine, but it won't get into the upper cylinder where the carbon would be to cause knocking/pinging.
There might be some fuel additives that could help with that issue to break down the carbon in the cylinder, but ARX generally can't help anything north of the rings other than cleaning up the oil return drains in your cylinder head, cleaning up the moving parts, and the lash adjusters.
Does premium/super premium fuel reduce it? For example, if your car takes 91, using 94?
GM makes an aerosol version of SeaFoam so you can spray it in through a vaccuum line and face as much risk of hydrolocking it. You'd probably foul your plugs and I would not do that without changing your oil right away.
I think ARX will help you but not with the issue of carbon on top of your pistons/in the combustion chamber, or piston slap.
aintaining GM Northstar V8 Engine
By Larry Carley, Technical Editor
The Northstar V8 engine family is General Motor's top-of-the-line luxury power plant. Introduced in 1993 in the Cadillac Allante, Eldorado and Seville STS, the 4.6L 32-valve dual overhead cam all-aluminum V8 engine was a quantum leap forward for U.S. automakers. Initially rated at 295 horsepower, the Northstar V8 has been ranked as one of the "10 Best Engines in North America" by Ward's Auto World. It also beat out both Mercedes-Benz and BMW in horsepower per liter of displacement, fuel economy and required maintenance.
Like most other engines, the Northstar V8 has evolved over the years. In 1994, the first Northstar V8 (L37) was joined by a second version (LD8) with a different cam profile that lowered peak horsepower slightly to 270 hp but increased torque output in the lower rpm range for improved throttle response and quick acceleration.
In 1994, a downsized and somewhat less powerful version of the original Northstar V8 was introduced in the Oldsmobile Aurora. The L47 4.0L V8 was essentially the same engine as the larger 4.6L V8 but with a smaller bore size (87mm vs. 93mm). The L47 4.0L V8 was rated at 250 horsepower.
In 1995, the power rating of the L37 4.6L V8 (VIN 9) was bumped up slightly to 300 hp, and the LD8 4.6L V8 (VIN Y) was upped to 275 hp.
The two basic versions of the 4.6L V8 (275 and 300 hp) are still being used in model year 2003, and there are no plans to replace this engine in the immediate future. So it looks like the Northstar V8 will continue to enjoy a long production run.
GM recently unveiled its Northstar XV12 concept engine that is physically about the same size as the existing V8 but is capable of producing up to 750 horsepower! The engine uses cylinder deactivation technology to keep fuel economy manageable, but there are no productions plans yet for this exotic power plant.
Engine Features
The Northstar V8 has a die-cast aluminum block with a bottom end girdle that splits along the midline of the crankshaft bearings. This takes the place of the main bearing caps. In model year 2000, GM began using a new high pressure "squeeze" casting process for the lower crankcase to reduce porosity in the aluminum, which may allow oil to seep through and leak (this has been a problem on some engines).
The cylinders have cast-in-place iron cylinder liners that are not replaceable. Compression up to model year 2000 was a relatively high 10.3:1. It was lowered to 10:1 in 2000. Each head has two camshafts (one intake, one exhaust) and four valves per cylinder (33mm intakes and 29mm exhausts). Direct-acting hydraulic lash adjusters are positioned over each valve. The overhead cams are all chain-driven, and use an intermediate chain sprocket under the front cover to connect to the crankshaft. Three separate hydraulic tensioners are used to keep the cam chains tight.
The Northstar V8 is an interference engine, which means if a chain fails or is disconnected when the engine is cranked over, the valves will hit the pistons. That's something you don't want to happen with an expensive engine like this!
The intake manifold is Nylon 66 thermoplastic, which helps cool intake air by conducting less heat from the engine. Fuel delivery is by sequential fuel injection with separate injectors mounted under the engine's top cover. Under the top cover you'll also find the MAP sensor, intake air temperature sensor and fuel pressure regulator.
If the fuel pump relay fails on a Northstar V8, the engine should still run because the fuel pump also can be energized through the oil pressure sending unit.
A four-coil distributorless ignition with a waste spark set up provides spark to the plugs. Two crankshaft position sensors are used (A and B) plus a camshaft position sensor to provide timing inputs. Both crank sensors are mounted in the block and the cam sensor is located on the rear head in front of the exhaust cam. There's also a knock sensor on the rear head between cylinders 1 and 3 to retard timing if detonation becomes a problem under load.
The ignition system has two modes of operation: "module mode" and "ignition control mode." In ignition control mode, the PCM controls ignition timing using sensor inputs. If there's a problem in the PCM or with its sensor inputs, the module mode takes over and runs the engine with a fixed 10 degrees of advance. The engine continues to run (essentially a limp-in mode) but with reduced performance.
In model year 2000, the DIS ignition system was changed to a coil-on-plug design, which eliminates the spark plug wires and waste spark. Each head has its own ignition module that fits in the middle of the valve cover.
Another feature of the Northstar engines is a "limp home" mode that allows the engine to continue running if all the coolant is lost. If the PCM senses an overheating condition, it temporarily disables up to half of the cylinders. This pumps enough air though the engine to keep temperatures from getting hot enough to cause any damage. Even so, GM says the vehicle should not be driven more than 50 miles in the limp-home mode.
Another unusual feature you may see is a liquid-cooled alternator on the DeVille and Seville. Cadillacs are crammed with electrical accessories that put quite a load on the charging system, so using liquid cooling helps prolong the life of the alternator. In 2001, GM went back to an air-cooled alternator to "eliminate the coolant tubes and potential leak points."
Maintenance
As for maintenance, there isn't much. One of GM's goals with the Northstar program was to reduce maintenance to a minimum. The engines are factory-equipped with 100,000-mile platinum-tipped spark plugs and five-year/150,000-mile Dex-Cool antifreeze, and use chain-driven cams to eliminate the need to replace timing belts. Except for oil and filter changes, there isn't much to maintain - unless something breaks.
The newer Northstar V8s use an "oil life monitor" light rather than a specific mileage interval or service schedule to indicate when oil changes are needed. The PCM tracks engine rpm, operating temperature, load, running time and ambient temperature to calculate oil life. Up until 1999, the maximum oil change interval under ideal conditions was 7,500 miles. In 2000, GM bumped the upper limit to 10,000 miles. In 2002, they did away with the upper limit altogether stretching the oil change interval to 12,000 miles or more, depending on operating conditions. However, GM does say the oil should be changed at least once a year regardless of mileage.
Note: When changing oil on a 4.6L Northstar V8, keep in mind that this engine holds 7.5 quarts instead of the more common 4 or 5 quarts.
We think pushing the oil change interval too far is asking for trouble. Changing the oil every 3,000 miles may be a conservative approach to engine maintenance, but considering the fact that most engines operate under less than ideal conditions, 3,000 miles is a realistic figure - especially during cold weather and for short trip, stop-and-go city driving. Oil is a lot cheaper than an engine - especially a Cadillac Northstar V8 engine.
In researching this engine, we discovered that few rebuilders are overhauling Northstar V8s - not because these engines are lasting forever (they're not) but because the Northstar V8s are such expensive and complex engines. Cadillac has no reman program for Northstar V8s (if one fails, replace it with a new one). None of the major production engine rebuilders are doing Northstar V8s, and some rebuilders told us certain critical internal parts are unavailable (such as oversize crankshaft bearings). Add to this the fact that the cylinder liners can't be replaced or overbored and it doesn't leave much to rebuild.
Even the heads are throw-aways, according to Cadillac. If the valve guides are worn, Cadillac says the cylinder heads need to be replaced. The heads have hard powder metal valve guides, but we don't see any reason why the guides can't be replaced with new ones or repaired with bronze or cast iron guide liners.
Problems & Recalls
As well-engineered as Northstar V8s are, like other engines they've had some problems. According to various sources, head gasket failures are not uncommon. Nor is oil burning or oil leaks.
Cadillac service bulletin 01-06-01-011 deals with oil burning on 1996-'99 Northstar V8s. The cure, says Cadillac, is to do a ring cleaning procedure (seems those long oil change intervals weren't such a good idea after all). Cadillac recommends using GM cleaning kit (P/N 12378545) and Kent-Moore J-45076 induction/evacuation tool to do the job. The cleaner is added into the cylinders through the spark plug holes and allowed to soak the rings for two hours. The cleaner and dissolved crud is then vacuumed out of the cylinders through the spark plug holes, followed by an oil change. Cleaning the throttle body and EGR valve is also recommended.
On 2000-'01 Northstar V8s, a buildup of carbon deposits in the combustion chamber can cause a cold knock condition. Bulletin 99-06-01-101A says to use top cleaner to remove the combustion chamber deposits.
If an engine has failed and is being rebuilt or replaced, the Engine Rebuilders Association (AERA) says the plastic intake manifold also should be replaced. The reason? Because of the complex shape of the manifold, it's impossible to tell if any engine debris has been blown back inside it. If the debris works loose and is ingested into the new engine, it will cause a repeat failure. That you don't want.
No oil pressure on a 1993-'94 engine? Debris between the oil pressure relief valve and its seat will prevent oil pressure buildup. The cure here is to clean or replace the pump (P/N 3543258), which is located on the front of the engine.
Oil leaks around the rear main crank seal have been a problem on some 1996-'99 engines, so GM has developed a new rear main oil seal (P/N 12556107) that should cure this problem. It's a press fit seal that takes a special tool (J-42482) to remove and install.
In 1995, GM revised the original crankshaft balancer to provide smoother operation and longer durability. If the balancer is removed from the crankshaft for any reason, GM recommends installing the newer, improved balancer (P/N 12552437 or 12552436, depending on the engine).
If you have to pull a cylinder head on a 1993-'99 4.0L or 4.6L Northstar V8 to replace a gasket or do a valve job, do not reuse the old 11mm head bolts. Also, GM has revised the head bolt torque values and tightening procedure as follows:
1. In sequence, torque all bolts to 30 ft.-lbs.
2. In sequence, rotate all bolts an additional 70°.
3. In sequence, rotate all bolts an additional 60°.
4. In sequence, rotate all bolts another 60°.
5. Torque the front three M6 head bolts to 106 in.-lbs.
Because the Northstar V8s are aluminum, thread damage is not unusual. GM's recommended thread repair kit is J42385-500 for main and head bolts, and J42385-2000 for other fasteners.
Accessing Diagnostic Codes
For driveability and emissions problems, you can access trouble codes and sensor data the usual way with a scan tool, or you can read the information through the Climate Control Center. To enter the built-in diagnostic service mode, press the OFF and WARMER buttons simultaneously and hold until all the segments on the display panel light up. If there are any engine or other trouble codes in memory, they will be displayed.
On the 1993-'95 models (pre-OBD II), trouble codes have a letter prefix, three-digits followed by a "C" for current or "H" for history code. On the 1996 and newer cars with OBD II, the prefixes are somewhat different and the codes are four-digit numbers.
On the earlier cars, engine codes have an "E" prefix. On the later OBD II cars, "P" is the prefix for powertrain.
Other codes on the earlier cars include "I" for instrument panel, "A" for the A/C system, "R" for the air bag system, "T" for ABS/traction control, and "S" for the electronic suspension. On the newer OBD II cars, the prefixes are different. You'll see "IP" for the IPC instrument panel, "AC" for air conditioning module, "TC" for traction control, "RS" for the road suspension system, "SD" for the air bags, "PZ" for the body control module, plus other codes for other accessories such as "CC" for the cell phone or "RF" for the integrated radio.
If there are no engine/powertrain codes in memory, the display will read "No E Code" or "No P Code" depending on the model year.
To check for other system codes, press the WARMER button to scroll ahead (or OFF to scroll backward). If the PCM can't communicate with a particular system, the display will read "No X Data" where X represents the letter(s) of the system.
To clear an engine code, choose PCM mode after any codes have been displayed, then scroll to CLEAR CODE, press the HI button to select, then press the HI button again to erase the code(s).
To exit the service diagnostic mode, press the AUTO or DEFOG button, or simply turn the ignition off. This does not erase any codes.
There's More, Lots More...
The built-in diagnostics provides access to each of the onboard electronic systems, which you can scroll through using the LO button. To select a system, press the HI button.
If you choose the PCM mode (powertrain control module/ engine), you can again use the LO button to scroll through more display options: DATA, INPUTS, OUTPUTS, OVERRIDES, CLEAR CODES and SNAPSHOT. As before, press HI to select your choice.
Under each of these categories are quite a list of things you can look at. Under PCM data, you can look at all the various sensor inputs, short-term and long-term fuel trim, injector pulse width, engine rpm, battery voltage and PROM identification. Under PCM INPUTS, you can check switch status (throttle position switch, brake pedal switch, transmission gear switches, etc.). Use the PCM OUTPUTS mode to check the EVAP and EGR systems, torque converter clutch solenoid, A/C compressor relay and transaxle solenoids.
The OVERRIDE mode under the PCM section allows you to override the various inputs to the PCM using the WARMER button to increase the value or the COOLER button to lower the value. Overrides include the TCC solenoid (mode PS01), EGR solenoid (PS02), idle speed control motor (PS03), disable individual fuel injectors (PS04), disable fuel pump relay (PS06), cruise control servo (PS07), cooling fan relay (PS08), spark timing advance (PS09), injector flow (PS10) and transaxle shift solenoids (PS10).
All artwork courtesy of General Motors Corp.
By Larry Carley, Technical Editor
The Northstar V8 engine family is General Motor's top-of-the-line luxury power plant. Introduced in 1993 in the Cadillac Allante, Eldorado and Seville STS, the 4.6L 32-valve dual overhead cam all-aluminum V8 engine was a quantum leap forward for U.S. automakers. Initially rated at 295 horsepower, the Northstar V8 has been ranked as one of the "10 Best Engines in North America" by Ward's Auto World. It also beat out both Mercedes-Benz and BMW in horsepower per liter of displacement, fuel economy and required maintenance.
Like most other engines, the Northstar V8 has evolved over the years. In 1994, the first Northstar V8 (L37) was joined by a second version (LD8) with a different cam profile that lowered peak horsepower slightly to 270 hp but increased torque output in the lower rpm range for improved throttle response and quick acceleration.
In 1994, a downsized and somewhat less powerful version of the original Northstar V8 was introduced in the Oldsmobile Aurora. The L47 4.0L V8 was essentially the same engine as the larger 4.6L V8 but with a smaller bore size (87mm vs. 93mm). The L47 4.0L V8 was rated at 250 horsepower.
In 1995, the power rating of the L37 4.6L V8 (VIN 9) was bumped up slightly to 300 hp, and the LD8 4.6L V8 (VIN Y) was upped to 275 hp.
The two basic versions of the 4.6L V8 (275 and 300 hp) are still being used in model year 2003, and there are no plans to replace this engine in the immediate future. So it looks like the Northstar V8 will continue to enjoy a long production run.
GM recently unveiled its Northstar XV12 concept engine that is physically about the same size as the existing V8 but is capable of producing up to 750 horsepower! The engine uses cylinder deactivation technology to keep fuel economy manageable, but there are no productions plans yet for this exotic power plant.
Engine Features
The Northstar V8 has a die-cast aluminum block with a bottom end girdle that splits along the midline of the crankshaft bearings. This takes the place of the main bearing caps. In model year 2000, GM began using a new high pressure "squeeze" casting process for the lower crankcase to reduce porosity in the aluminum, which may allow oil to seep through and leak (this has been a problem on some engines).
The cylinders have cast-in-place iron cylinder liners that are not replaceable. Compression up to model year 2000 was a relatively high 10.3:1. It was lowered to 10:1 in 2000. Each head has two camshafts (one intake, one exhaust) and four valves per cylinder (33mm intakes and 29mm exhausts). Direct-acting hydraulic lash adjusters are positioned over each valve. The overhead cams are all chain-driven, and use an intermediate chain sprocket under the front cover to connect to the crankshaft. Three separate hydraulic tensioners are used to keep the cam chains tight.
The Northstar V8 is an interference engine, which means if a chain fails or is disconnected when the engine is cranked over, the valves will hit the pistons. That's something you don't want to happen with an expensive engine like this!
The intake manifold is Nylon 66 thermoplastic, which helps cool intake air by conducting less heat from the engine. Fuel delivery is by sequential fuel injection with separate injectors mounted under the engine's top cover. Under the top cover you'll also find the MAP sensor, intake air temperature sensor and fuel pressure regulator.
If the fuel pump relay fails on a Northstar V8, the engine should still run because the fuel pump also can be energized through the oil pressure sending unit.
A four-coil distributorless ignition with a waste spark set up provides spark to the plugs. Two crankshaft position sensors are used (A and B) plus a camshaft position sensor to provide timing inputs. Both crank sensors are mounted in the block and the cam sensor is located on the rear head in front of the exhaust cam. There's also a knock sensor on the rear head between cylinders 1 and 3 to retard timing if detonation becomes a problem under load.
The ignition system has two modes of operation: "module mode" and "ignition control mode." In ignition control mode, the PCM controls ignition timing using sensor inputs. If there's a problem in the PCM or with its sensor inputs, the module mode takes over and runs the engine with a fixed 10 degrees of advance. The engine continues to run (essentially a limp-in mode) but with reduced performance.
In model year 2000, the DIS ignition system was changed to a coil-on-plug design, which eliminates the spark plug wires and waste spark. Each head has its own ignition module that fits in the middle of the valve cover.
Another feature of the Northstar engines is a "limp home" mode that allows the engine to continue running if all the coolant is lost. If the PCM senses an overheating condition, it temporarily disables up to half of the cylinders. This pumps enough air though the engine to keep temperatures from getting hot enough to cause any damage. Even so, GM says the vehicle should not be driven more than 50 miles in the limp-home mode.
Another unusual feature you may see is a liquid-cooled alternator on the DeVille and Seville. Cadillacs are crammed with electrical accessories that put quite a load on the charging system, so using liquid cooling helps prolong the life of the alternator. In 2001, GM went back to an air-cooled alternator to "eliminate the coolant tubes and potential leak points."
Maintenance
As for maintenance, there isn't much. One of GM's goals with the Northstar program was to reduce maintenance to a minimum. The engines are factory-equipped with 100,000-mile platinum-tipped spark plugs and five-year/150,000-mile Dex-Cool antifreeze, and use chain-driven cams to eliminate the need to replace timing belts. Except for oil and filter changes, there isn't much to maintain - unless something breaks.
The newer Northstar V8s use an "oil life monitor" light rather than a specific mileage interval or service schedule to indicate when oil changes are needed. The PCM tracks engine rpm, operating temperature, load, running time and ambient temperature to calculate oil life. Up until 1999, the maximum oil change interval under ideal conditions was 7,500 miles. In 2000, GM bumped the upper limit to 10,000 miles. In 2002, they did away with the upper limit altogether stretching the oil change interval to 12,000 miles or more, depending on operating conditions. However, GM does say the oil should be changed at least once a year regardless of mileage.
Note: When changing oil on a 4.6L Northstar V8, keep in mind that this engine holds 7.5 quarts instead of the more common 4 or 5 quarts.
We think pushing the oil change interval too far is asking for trouble. Changing the oil every 3,000 miles may be a conservative approach to engine maintenance, but considering the fact that most engines operate under less than ideal conditions, 3,000 miles is a realistic figure - especially during cold weather and for short trip, stop-and-go city driving. Oil is a lot cheaper than an engine - especially a Cadillac Northstar V8 engine.
In researching this engine, we discovered that few rebuilders are overhauling Northstar V8s - not because these engines are lasting forever (they're not) but because the Northstar V8s are such expensive and complex engines. Cadillac has no reman program for Northstar V8s (if one fails, replace it with a new one). None of the major production engine rebuilders are doing Northstar V8s, and some rebuilders told us certain critical internal parts are unavailable (such as oversize crankshaft bearings). Add to this the fact that the cylinder liners can't be replaced or overbored and it doesn't leave much to rebuild.
Even the heads are throw-aways, according to Cadillac. If the valve guides are worn, Cadillac says the cylinder heads need to be replaced. The heads have hard powder metal valve guides, but we don't see any reason why the guides can't be replaced with new ones or repaired with bronze or cast iron guide liners.
Problems & Recalls
As well-engineered as Northstar V8s are, like other engines they've had some problems. According to various sources, head gasket failures are not uncommon. Nor is oil burning or oil leaks.
Cadillac service bulletin 01-06-01-011 deals with oil burning on 1996-'99 Northstar V8s. The cure, says Cadillac, is to do a ring cleaning procedure (seems those long oil change intervals weren't such a good idea after all). Cadillac recommends using GM cleaning kit (P/N 12378545) and Kent-Moore J-45076 induction/evacuation tool to do the job. The cleaner is added into the cylinders through the spark plug holes and allowed to soak the rings for two hours. The cleaner and dissolved crud is then vacuumed out of the cylinders through the spark plug holes, followed by an oil change. Cleaning the throttle body and EGR valve is also recommended.
On 2000-'01 Northstar V8s, a buildup of carbon deposits in the combustion chamber can cause a cold knock condition. Bulletin 99-06-01-101A says to use top cleaner to remove the combustion chamber deposits.
If an engine has failed and is being rebuilt or replaced, the Engine Rebuilders Association (AERA) says the plastic intake manifold also should be replaced. The reason? Because of the complex shape of the manifold, it's impossible to tell if any engine debris has been blown back inside it. If the debris works loose and is ingested into the new engine, it will cause a repeat failure. That you don't want.
No oil pressure on a 1993-'94 engine? Debris between the oil pressure relief valve and its seat will prevent oil pressure buildup. The cure here is to clean or replace the pump (P/N 3543258), which is located on the front of the engine.
Oil leaks around the rear main crank seal have been a problem on some 1996-'99 engines, so GM has developed a new rear main oil seal (P/N 12556107) that should cure this problem. It's a press fit seal that takes a special tool (J-42482) to remove and install.
In 1995, GM revised the original crankshaft balancer to provide smoother operation and longer durability. If the balancer is removed from the crankshaft for any reason, GM recommends installing the newer, improved balancer (P/N 12552437 or 12552436, depending on the engine).
If you have to pull a cylinder head on a 1993-'99 4.0L or 4.6L Northstar V8 to replace a gasket or do a valve job, do not reuse the old 11mm head bolts. Also, GM has revised the head bolt torque values and tightening procedure as follows:
1. In sequence, torque all bolts to 30 ft.-lbs.
2. In sequence, rotate all bolts an additional 70°.
3. In sequence, rotate all bolts an additional 60°.
4. In sequence, rotate all bolts another 60°.
5. Torque the front three M6 head bolts to 106 in.-lbs.
Because the Northstar V8s are aluminum, thread damage is not unusual. GM's recommended thread repair kit is J42385-500 for main and head bolts, and J42385-2000 for other fasteners.
Accessing Diagnostic Codes
For driveability and emissions problems, you can access trouble codes and sensor data the usual way with a scan tool, or you can read the information through the Climate Control Center. To enter the built-in diagnostic service mode, press the OFF and WARMER buttons simultaneously and hold until all the segments on the display panel light up. If there are any engine or other trouble codes in memory, they will be displayed.
On the 1993-'95 models (pre-OBD II), trouble codes have a letter prefix, three-digits followed by a "C" for current or "H" for history code. On the 1996 and newer cars with OBD II, the prefixes are somewhat different and the codes are four-digit numbers.
On the earlier cars, engine codes have an "E" prefix. On the later OBD II cars, "P" is the prefix for powertrain.
Other codes on the earlier cars include "I" for instrument panel, "A" for the A/C system, "R" for the air bag system, "T" for ABS/traction control, and "S" for the electronic suspension. On the newer OBD II cars, the prefixes are different. You'll see "IP" for the IPC instrument panel, "AC" for air conditioning module, "TC" for traction control, "RS" for the road suspension system, "SD" for the air bags, "PZ" for the body control module, plus other codes for other accessories such as "CC" for the cell phone or "RF" for the integrated radio.
If there are no engine/powertrain codes in memory, the display will read "No E Code" or "No P Code" depending on the model year.
To check for other system codes, press the WARMER button to scroll ahead (or OFF to scroll backward). If the PCM can't communicate with a particular system, the display will read "No X Data" where X represents the letter(s) of the system.
To clear an engine code, choose PCM mode after any codes have been displayed, then scroll to CLEAR CODE, press the HI button to select, then press the HI button again to erase the code(s).
To exit the service diagnostic mode, press the AUTO or DEFOG button, or simply turn the ignition off. This does not erase any codes.
There's More, Lots More...
The built-in diagnostics provides access to each of the onboard electronic systems, which you can scroll through using the LO button. To select a system, press the HI button.
If you choose the PCM mode (powertrain control module/ engine), you can again use the LO button to scroll through more display options: DATA, INPUTS, OUTPUTS, OVERRIDES, CLEAR CODES and SNAPSHOT. As before, press HI to select your choice.
Under each of these categories are quite a list of things you can look at. Under PCM data, you can look at all the various sensor inputs, short-term and long-term fuel trim, injector pulse width, engine rpm, battery voltage and PROM identification. Under PCM INPUTS, you can check switch status (throttle position switch, brake pedal switch, transmission gear switches, etc.). Use the PCM OUTPUTS mode to check the EVAP and EGR systems, torque converter clutch solenoid, A/C compressor relay and transaxle solenoids.
The OVERRIDE mode under the PCM section allows you to override the various inputs to the PCM using the WARMER button to increase the value or the COOLER button to lower the value. Overrides include the TCC solenoid (mode PS01), EGR solenoid (PS02), idle speed control motor (PS03), disable individual fuel injectors (PS04), disable fuel pump relay (PS06), cruise control servo (PS07), cooling fan relay (PS08), spark timing advance (PS09), injector flow (PS10) and transaxle shift solenoids (PS10).
All artwork courtesy of General Motors Corp.
Originally Posted By: Frank
On 2000-'01 Northstar V8s, a buildup of carbon deposits in the combustion chamber can cause a cold knock condition. Bulletin 99-06-01-101A says to use top cleaner to remove the combustion chamber deposits.
AC Delco Top Engine Cleaner X66A (aerosol) or X66P (pour.)
It's basically the exact same stuff as SeaFoam, and it is nasty but boy does it ever work. I would only use it on the top end, and if you are not sure how to do it yourself have the dealer do it so if they hydrolock it and break your engine, you're not out a motor. The aerosol is friendlier to do because it's a much more limited amount that goes into the engine. Suck it into the engine, let it sit and soak, go drive the living [censored] out of it and then change the oil immediately as all the carbon that breaks off/flakes out from the increased combustion chamber temperatures and solvent effects of it soaking in as well as any of it that drained down thins your oil. It might foul your plugs if any of that carbon gets caught up in the electrode.
AutoRX can help you with other problems in this engine but I would take GM's word and a knowledge of how ARX works to go solve your problem with something different.
On 2000-'01 Northstar V8s, a buildup of carbon deposits in the combustion chamber can cause a cold knock condition. Bulletin 99-06-01-101A says to use top cleaner to remove the combustion chamber deposits.
AC Delco Top Engine Cleaner X66A (aerosol) or X66P (pour.)
It's basically the exact same stuff as SeaFoam, and it is nasty but boy does it ever work. I would only use it on the top end, and if you are not sure how to do it yourself have the dealer do it so if they hydrolock it and break your engine, you're not out a motor. The aerosol is friendlier to do because it's a much more limited amount that goes into the engine. Suck it into the engine, let it sit and soak, go drive the living [censored] out of it and then change the oil immediately as all the carbon that breaks off/flakes out from the increased combustion chamber temperatures and solvent effects of it soaking in as well as any of it that drained down thins your oil. It might foul your plugs if any of that carbon gets caught up in the electrode.
AutoRX can help you with other problems in this engine but I would take GM's word and a knowledge of how ARX works to go solve your problem with something different.
Thanks Frank, I read that one sometime ago. I am one of the few that does my own work on a newer Caddy Northstar. Cuz I surf BITOG so much, I have tried the MMO, Tectron, SLOB and all the other fun stuff at least once. ( Not all on the same car mind you . )
It's not that big of a problem, but seems nobody else reports what they do on these motors. I have been tweaking it for about 5 months now, and I almost have it exactly the way I want it. I have run every fuel from 104 to 87. It seems to like 91 with a small dose of MMO.
I just did not want to take it to the dealer, as I have already been sent away when I asked them to check the ATF fluid level after I changed it.
They couldn't do it. Didn't have the tool. Boy they got mad when I reached in my pocket and pulled out my custom made T40 tool and asked them if they would like to rent mine .... Check plug with less than a half inch from the exhaust header and it has to be checked hot... Shame on you GM... Good news is that my hand healed in about 2 weeks and I found a better way..
I ordered 6 bottles so I am going to be Rxing a 97 Toyota corolla with 70K and cheap dino changes also. That will be a good one.
I have 2 2 hour drives a week at pretty good speed, so I should be ready for a rinse in about 3 - 4 weeks. Will keep you posted. Thanks again, and sorry for rambling on.
It's not that big of a problem, but seems nobody else reports what they do on these motors. I have been tweaking it for about 5 months now, and I almost have it exactly the way I want it. I have run every fuel from 104 to 87. It seems to like 91 with a small dose of MMO.
I just did not want to take it to the dealer, as I have already been sent away when I asked them to check the ATF fluid level after I changed it.
They couldn't do it. Didn't have the tool. Boy they got mad when I reached in my pocket and pulled out my custom made T40 tool and asked them if they would like to rent mine .... Check plug with less than a half inch from the exhaust header and it has to be checked hot... Shame on you GM... Good news is that my hand healed in about 2 weeks and I found a better way..
I ordered 6 bottles so I am going to be Rxing a 97 Toyota corolla with 70K and cheap dino changes also. That will be a good one.
I have 2 2 hour drives a week at pretty good speed, so I should be ready for a rinse in about 3 - 4 weeks. Will keep you posted. Thanks again, and sorry for rambling on.
Originally Posted By: MGregoir
GM makes an aerosol version of SeaFoam so you can spray it in through a vaccuum line and face as much risk of hydrolocking it. You'd probably foul your plugs and I would not do that without changing your oil right away.
Seafoam makes their own aerosol version thats probably cheaper and easier to find than the GM version.
GM makes an aerosol version of SeaFoam so you can spray it in through a vaccuum line and face as much risk of hydrolocking it. You'd probably foul your plugs and I would not do that without changing your oil right away.
Seafoam makes their own aerosol version thats probably cheaper and easier to find than the GM version.
Yup.. Used the aerosol seafoam. I just did not let it sit overnight, just about 20mins. I think the GM stuff screws onto a schader ( sp ? ) valve of some sort, I might try it. I think I will need plugs by that point, but those will be last to go in after all the clean up attempts.
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Originally Posted By: Frank
What kind of rinse our you doing ? this is the most important part of the application. Suggest you e-mail Gay Allan and Barkerman
and make your choice.
In case PF is interested, I'd kinda lean to two shorter rinse cycles with the two bottle application. Let me say that this is opinion based on observations and some testing.
I'd run it for the 1000 miles (doesn't have to be exact) then do two 1000-1500 mile rinse cycles. My feeling is that this "fast track" application can benefit from a refreshed sump in a shorter time frame. This would be even more important in a known sludge engine, imo.
What kind of rinse our you doing ? this is the most important part of the application. Suggest you e-mail Gay Allan and Barkerman
and make your choice.
In case PF is interested, I'd kinda lean to two shorter rinse cycles with the two bottle application. Let me say that this is opinion based on observations and some testing.
I'd run it for the 1000 miles (doesn't have to be exact) then do two 1000-1500 mile rinse cycles. My feeling is that this "fast track" application can benefit from a refreshed sump in a shorter time frame. This would be even more important in a known sludge engine, imo.
My mom's '03 Malibu has the cold piston slap too, think this is the same situation? Her motor is the 3.1 V6. It's always had 3k oil changes.
2 quick changes ? Even with such a large 8qt sump ? I don't mind doing it, but I don't think it's sludged up that bad. Maybe I will do the second rinse with dino and I will wait for the OLM to get to say 50%. That will be around 5K miles, then dump and go back to syn. The motor sounds better, but it has warmed up here a bit.
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Originally Posted By: porkfarm
2 quick changes ? Even with such a large 8qt sump ? I don't mind doing it, but I don't think it's sludged up that bad. Maybe I will do the second rinse with dino and I will wait for the OLM to get to say 50%. That will be around 5K miles, then dump and go back to syn. The motor sounds better, but it has warmed up here a bit.
That's if you're in a hurry. No need otherwise ..and, in that case, there was no need for 2 bottles in the sump. The same amount of Auto-Rx would be cleaning the same piston ring area and other surfaces that it would in ...hmmm..somewhere between a 5-6 quart small and big block Chevy.
Your engine has no more mass or surface area than many others. It's sump size is part of a service design or performance design buffer.
That is, I don't really see a need for the two short rinse treatments. You can just go about your business after the clean phase as long as you're not using PAO or ester based oils ..but most people are impatient. Now if you had heavy sludge, I'm thinking two bottles and the shorter rinse cycles would really pay off. I probably should add "with some intermediate filter changes".
2 quick changes ? Even with such a large 8qt sump ? I don't mind doing it, but I don't think it's sludged up that bad. Maybe I will do the second rinse with dino and I will wait for the OLM to get to say 50%. That will be around 5K miles, then dump and go back to syn. The motor sounds better, but it has warmed up here a bit.
That's if you're in a hurry. No need otherwise ..and, in that case, there was no need for 2 bottles in the sump. The same amount of Auto-Rx would be cleaning the same piston ring area and other surfaces that it would in ...hmmm..somewhere between a 5-6 quart small and big block Chevy.
Your engine has no more mass or surface area than many others. It's sump size is part of a service design or performance design buffer.
That is, I don't really see a need for the two short rinse treatments. You can just go about your business after the clean phase as long as you're not using PAO or ester based oils ..but most people are impatient. Now if you had heavy sludge, I'm thinking two bottles and the shorter rinse cycles would really pay off. I probably should add "with some intermediate filter changes".
so it's not a ratio thing then eh ? My mindset was that it would get diluted down. So if I understand you correctly, it is more like a one size fits all. Just as long as the ARX touches the surfaces, it's good. I will use just one in the Jag and go with normal procedure as that valve train is quiet.
As an update, day 4 and the motor has never been this quiet.
As an update, day 4 and the motor has never been this quiet.
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Quote:
so it's not a ratio thing then eh ?
Well, yes it is. You've got double the current "normal" add in there. That's how I reason it. Your sump wouldn't warrant 2 bottles in a normal treatment. I'm sure that there's a fudge factor in ratios
So, and this is my opinion, it's down to how fast you want your results ....and, as with all things, YMMV.
Let's say you're into synthetics and do extended drains. You probably want to get back to it in as timely a manner as possible. This would be one way, imo, to accomplish this without any degradation in results.
so it's not a ratio thing then eh ?
Well, yes it is. You've got double the current "normal" add in there. That's how I reason it. Your sump wouldn't warrant 2 bottles in a normal treatment. I'm sure that there's a fudge factor in ratios
So, and this is my opinion, it's down to how fast you want your results ....and, as with all things, YMMV.
Let's say you're into synthetics and do extended drains. You probably want to get back to it in as timely a manner as possible. This would be one way, imo, to accomplish this without any degradation in results.
It worked !! The car was just about silent when I started it this morning ! I have tried seafoam, maxlife red bottle, pen plat, and a maint dose of ARX along with a host of other BITOG favorite cleaners in the gas tank, but this is the first time since I owned this car that I am happy with how it sounds !! Now after my rinse I am going to have to find a 5W30 that keeps it that way. Maybe even M1 like it says on the oil cap, but I have time to make that choice.
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