GM ENGINES KNOCK

[Last_Z]

Terry,
As I mentioned on the other 2 threads; someone mentioned about a TSB on these pumps. The guy stated a faulty o-ring that caused cavitation and excessive noise from the pump.
I also think that the "Piston Slap" problem might be a bit overblown by the enthusiasts. I think "most of them" have been blaming the wrong thing. Don't get me wrong, these cars DO suffer from cold start slap, but I'm betting many of the "slappers" are actually suffering from bad pumps.

I'd go out on a limb and give my expert opinion

and say that at least on Chris' engine as well as mine, the piston slap should not affect durability since Al is very low and iron is relatively low for these two large engines, besides the fact that at least mine was driven hard!
I have also had the chance to listen to some of our pick up trucks at work and they also make the valve clatter noise, although much less noticeable. Do P/Us use the same pump type?

These pumps obviously need more investigating as it seems more and more they are the cause for the high copper and "diesel engine" sound.
Rick

 

[Chris B.]

This is great stuff! A big thanks to Moto and Terry for tha help!

What does Cavation mean and how is it caused?

If the oil pump is at fault how can you tell if it is going out befor the engine is damaged.

 

[TooSlick]

Cavitation is a process that happens when flow separation occurs, and/or gas bubbles violently collapse on a surface and cause pitting wear. It occurs with turbopumps, boat/submarine/PWC propellers and on the "wet sleeves" of certain types of diesel engines, like the 7.3L Ford Powerstokes ...In the last case, it is caused by a particular type of "nucleate boiling" behavior that is compounded by vibration.

 

[jsharp]

Anyone have any data collection equipment that uses a notebook PC and takes standard pressure transducers? You should be able to identify and log these oil pressure fluctuations easily.

I'd don't have any of that equipment anymore since I'm pretty much out of that kind of business. I'd be glad to loan it to the cause though if I did...

 

[Last_Z]

Chris,
The cavitation we are referring to here occurs inside the oil pump....at least that's the theory.

jsharp,
Terry thorizes that this cavitation pulsates very quickly and does not show a drop in oil pressure.....at least not at the gauge but does create the noise we hear.

 

[Terry]

jsharp is correct that the variations in output could be measured with the transducer setup he recommends even though the guage or light is not registering it.

Even at high freq short duration at low to mid rpm I am guessing at.

 

[LS1WhiteWs6]

2001 Trans Am Ws6

Miles on car - 25,731
Miles on oil - 3,821
Oil Type - Mobil 1 10W/30

Aluminum - 4
Chromium - 1
Iron - 17
Copper - 42
Lead - 5
Tin - 2
Molybdenum - 65
Nickel - 1
Manganese - 1
Silver - 0
Titanium - 0
Potassium - 0
Boron - 126
Silicon - 12
Sodium - 6
Calcium - 2832
Magnesium - 37
Phosphorus - 699
Zinc - 943
Barium - 0

SUS Viscosity @ 210* - 60.8
Flashpoint - 370*
Fuel % - Antifreeze % - 0.0
Water % - 0.0
Insolubles % - 0.3

K&N Filter. I added about 1qt during the interval.

Here is my 1st UOA on the car since i've had it. I do hear the diesel engine noise sometimes. Also i have knocking/ticking sounds in the engine bay. Sometimes it knocks loud and you can stand about 2 car lengths from it and still hear the knocking.

 

[JohnBrowning]

Jason you are right that they are of simalar design. THe reason they are not driveing it off they want to minimize unsupported crank "nose" length. This reduces crank "nose" deflection (torsional and radial). An oil pump drive is very picky about run out but a cam is not. They are also getting away from puting pumps in front cover because of the noise transmission problems.

I have not had to tear an LS1 pump apart. I can tell you that alot of noise can be elimanted by proper port timeing to creat precompression prior to discharge. This will reduce pressure ripples at higher speeds. You can control this buy playing around with angular spaceing of adjacent lobes. You then add things like steeped lands, noise slots,mettering groves The inlet anddishcharge ports shold be inline with the direction of flow.You can get a lot of whistleing from a poorly designed pump! SOme of the Northstar designs had poorly designed pumps that had 180 degree turn for suction and discharge in relationship to the direction of rotation and main oil galley postion.

The bad thing about gerotor pumps is that the suction side must stay air tight, have smooth flow, must have rigid houseings, must be machined to close tolerences.....

This is interesting. I once considered this area as a possable source of problems but quickly dismissed it. I guess I should have opened the oil pump and taken a peak. I think that you are right on track that this may be an indexing problem!!

I have not heard about a diesel sound. Is this like a ticking noise? If so then this same type of problem was delt with on the DUramax diesel. Isuzu found out that intermintent cavatation in the lower porption of the main bearings was causeing this tick sound. THe soultion was to make a 1mm grove in the lower bearing.
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[ December 10, 2003, 11:53 PM: Message edited by: JohnBrowning ]

 

[Last_Z]

Almost forgot....
Thanks Moto, Terry and BITOG!
You guys and this site rock

 

[Last_Z]

Uh huh!
Went to AllData.com come and found these TSBs:

#17- 02-06-01-038 DEC 02 Engine - Knocking or Lifter Noise

#20- 02-06-01-029 SEP 02 Engine - Needle Bearings Found Upon Oil Change

 

[Drew99GT]

quote:

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Originally posted by Last_Z:
Uh huh!
Went to AllData.com come and found these TSBs:

#17- 02-06-01-038 DEC 02 Engine - Knocking or Lifter Noise

#20- 02-06-01-029 SEP 02 Engine - Needle Bearings Found Upon Oil Change

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OUCH!!!!!!

 

[vettenuts]

In answer to the prior questions, I have an 02 Vette with the LS-1. I posted my prior UOA last year and am using Amsoil 5W-30 ASL. My motor has a slight ticking when started, not a real "slap" like I hear in my Pontiac 3.1. I did take the car on a long trip this past summer (Vette 50rh anniversary

) and drove most of the return in 6th gear with the motor turning slow RPM's. The morning after returning home, when I started it, the motor was so loud that I actually shut it off thinking something had happened. It has never been that loud since. I was told by a GM tech to use GM part # 12345515, which is a top engine cleaner added to the fuel. That seemed to help and I have continued to use this on occasion, but when it is cold I still get a noise that many have called piston slap. Buy my car has the new pistons and rings (coated pistons and higher pressure Napier rings) that were installed in 02. Based on my experience, it sound more like lifter noise but not one that has totally lost oil. It's more a noise of my old Ford that had a lot of miles, the valve train was noisy. But it does quiet down once the motor has warmed up. Some mornings are worse then others, and there is not a readily apparent correlation to outside temperature which is interesting as well.

One thing I did notice upon my return this summer, the motor felt "more free" if you can understand that. It just seemed to rev and run more effortlessly. Kind of hard to explain I guess. One thing hasn't changed, the car runs very very strong

 

[Last_Z]

JB,

This is the sound I call "Diesel Sound" or "Low oil" sound. I get this sound about 30 seconds to one minute after a cold start up. It is always present, although it does quiet down considerably when the coolant teperatures show above 210*F. I'm begining to wonder if my 160*F T-stat is too cold?
I am almost 100% convinced this is lifter clatter.

Rick

 

[Chris B.]

quote:

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Originally posted by Last_Z:
JB,

This is the sound I call "Diesel Sound" or "Low oil" sound. I get this sound about 30 seconds to one minute after a cold start up. It is always present, although it does quiet down considerably when the coolant teperatures show above 210*F. I'm begining to wonder if my 160*F T-stat is too cold?
I am almost 100% convinced this is lifter clatter.

Rick

---

Dito!

I bet we have put in more time figuering this problem out then GM has! I think we should be put on GM's pay role!

 

[Last_Z]

ChrisB,
No Sheet!?

We should at least get the fix, don't you think?

Anyway, I let the engine's temperature reach 210*F again, and once more the sound diminish considerably.
Does anyone have any theories as to what is temperature's role in this equation? Thinner oil flowing better? Pump clearance tightening?

Rick

 

[jsharp]

quote:

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Originally posted by Terry:
jsharp is correct that the variations in output could be measured with the transducer setup he recommends even though the guage or light is not registering it.

Even at high freq short duration at low to mid rpm I am guessing at.

---

Yep, that was my point. The gauge and possibly the position of the sender act as a dampener and rapid changes are masked.

Pressure drop means less or no flow though the oiling system. Probably not too harmful for brief periods but not a good thing if it happens too often.

To get real measurements you need real instruments...

[ December 11, 2003, 04:55 PM: Message edited by: jsharp ]

 

[ajax]

The noise my LS1 makes,is only at 2000 to 2300 rpm's at a light load,it won't do it if you just rev it,has to have a load.I can do it at a stop,by reving it,and releasing clutch a little bit,have only done it once for the tech at dealer,so he,replaces clutch,when you can hear it from the left side of engine,to me,sounds like a piston is rocking,in its bore.thanks

 

[Jared H]

Just adding my info for the record ... I've also previously posted my last UOA(Blackstone Labs) with M1 10W30 at 5300 miles.

My 02 z28 A4 (LS1) makes a slight "diesel" or "slap" sound at cold start which diminishes somewhat when the engine is up to operating temperatures (stock thermostat), but not completely. I do not believe the sound I'm hearing to be lifter noise. If "it" is, in fact, "piston slap", I believe I've only got one piston with the issue. FWIW, my 2000 z28 (LS1) did not have this issue.

When warm and in park(or neutral), you really have to listen to hear the noise. But put the car in Drive or Reverse (now loaded) the sound is more apparent. The noise is either indiscernable or gone when engine rpm exceeds about 2500rpm regardless of engine temp.

I'll be posting my UOA results for my next oil change(M1 0W40) at some point in the future (probably near June of 04).

Terry you can add me to your list of UOA customers reporting a "dieseling" sound in their LS1.

On the upside, my car runs great (IMO, of course). I just ran a 13.2x at 105.XX the last Friday (12/19/03) before Christmas on street tires with my only modifications being a Lid and a SLP dual/dual (muffler only). Air quality was excellent. Track was/is in Houston.

 

[Motorbike]

quote:

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Originally posted by Jared H:



My 02 z28 A4 (LS1) makes a slight "diesel" or "slap" sound at cold start which diminishes somewhat when the engine is up to operating temperatures (stock thermostat), but not completely. I do not believe the sound I'm hearing to be lifter noise

---

See my newest thread topic on this in the General and Off Topic Section " LS1 Lifter Noise Revisisted "

It's the oil pickup screen/tube and a bad sealing o'ring sucking air or fitting and the General already has a TSB on it .

What the General don't say is.....

Even though the pump when primed is a source for the copper/bronze when the gerotor style pumps loose their prime by nature of the design more wear metal will be shed off that thing into the oil .

 

[Von]

Hi Everyone - This is my first post:

2001 Chevy Silverado 2500 4X4
Titan Labs done in Jan 2003
K&N air filter
Oil is Amsoil Series 2000 0W-30
Amsoil oil filter
Put in truck at 19300, changed at 27261 for 7961 on oil, some gas additive used during this period.
Previous oil was same, so not first Amsoil use.
Magnetic drain plug was clean (latest change had a little dark gray color on magnet, but no fuzz).
This truck has CSK/piston slap. Not horrible, but pretty noticable at certain temperatures (40 degree range is worst).
I'm at 34,000+ and have to make a decision to get extended warranty or not (Chevy is offering on CSK motors) which kills resale value due to bad engine (unless you want a new engine in which case it is normal).
Truck has great power, gas mileage, etc and uses about a quart in 5000 miles. But knocks until it has been run about 10 minutes.
Has Superchip programmer.
Tows 5000 pounds about once per month.

Titan doesn't list amounts on their report unless you ask, and so I called and got the following values:

Weight of oil: 40W
TBN: 14.1
Water: less than .1%
Fuel: less than 1.0%
Anti-freeze: less than .1%
Chromium: 1
Copper: 24
Iron: 32
Lead: 11
Tin: 2
Aluminum: 3
Silicon: 10

Titan considers all of this to be within spec except the 40W and they questioned if I had exceeded Chevy's recommended interval (no by the computer monitor and Amsoil rates to 35000).

I am new at this, but I'm a little concerned about the iron.
Otherwise it looks good since thses motors seem to ooze copper.
Question is, is there a better oil for a CSK GM engine or is this as good as it gets considering 8000 miles?
Is 0W-30 too light for towing? The Amsoil tech rep said it was the best and didn't seem to care about the CSK or the towing.
Titan said no sign of piston slap.
Get the extended (we now know not to take your trade-in) warranty?
Comments Please!!
Thanks in advance. Von