GM 3800 Series II coolant loss - but where?

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I thought that once this happened to me, it would be obvious that the intake gasket has gone bad.... but I'm not sure what I'm seeing here.

1999 Buick Park Avenue, only 75,000 miles. 3800 Series II, non-supercharged.

Oil (PP 10w-30) currently has 5,000 miles on it, and is right at 1 quart low (which seems normal for this car, after 5,000 miles of driving). Oil was last changed in early summer.

Coolant reservoir is empty (THIS is what bothers me.)

I don't know where the coolant went. Every time I lift the hood, I check the coolant in the overflow FIRST. Last time I was under the hood, it seemed like it was a little lower than usual.

Radiator is full.

My first thought was that the intake gasket finally went bad, but the oil level is exactly where I expect it to be. It is one quart low after 5,000 miles of driving, which seems normal to me for this car.

There was a small amount of clear condensation under the oil cap, but I'm not surprised by that, with a car that has most of it's driving done 2-8 miles at a time. (This car only sees about 7,000 miles a year).

The oil is not foamy or frothy, it looks completely normal on the dipstick... just a little dark, of course. I did not see any evidence of anything out of the ordinary when shining a light through the oil filler hole...which is quite large on this car. No appearance of water in the oil at all.

Dad commented that he has seen occasional small puddles of what he assumed was water under the car (under where the engine would be on the garage floor), but didn't think much about it.

If the engine had taken in a quart or two of coolant, shouldn't my oil level be higher than it is... and wouldn't the oil appear to be contaminated? The oil level is right where I'd expect it to be, and looks like I'd expect it to look.

I've told him to stop driving it at this point, until I can make some sense of this. It is ready for an oil change anyway, which I'm going to do on Monday morning.

Even though the OLM is still at 24%, with all of the short trips that this car does, and with winter around the corner, I'm going to change it now.

Unless something becomes obvious between now and then, I'm going to take a sample on Monday and send it off to Blackstone in Fort Wayne. I have a neighbor who manages a construction equipment dealership, and they have fluids tested all of the time. I may use whoever he uses for testing, I'm going to talk to him about this later tonight.

Right now, I'm planning on refilling it with whatever oil I can find that is cheap (Wal*Mart 10w-30) and a NAPA ProSelect filter.

Since it has been leaking small puddles of "something", I guess it is possible that there's an external leak... maybe a loose hose or the water pump is getting ready to go. When I get it up on the ramps in my garage on Monday, I'll be able to look everything over for a leak as well.

Thoughts?
 
My State-issued 2006 Chevrolet Malibu started mysteriously losing coolant from the first month on the road. It was back to the dealer (warranty) 5 different times for this problem. They changed hoses, clamps, thermostat, caps, etc. Finally, the 5th time they found that the heater core was defective from the factory. The coolant was leaking between the instrument panel and firewall, slowly pooling under the rug. It was a mess!
 
Originally Posted By: Warstud
Remove the plastic cover off the engine and look for puddles of coolant around the intake.


I did pull off the cover and look around the plastic intake.

I did not see any evidence of Dex-Cool around the intake. The intake gasket is seeping a little engine oil (which doesn't surprise me much for a 10 year old car).
 
There are many lawsuits over that motor due to bad gasket materials and poor engineering . Contrary to popular beliefs , it is not due to dex-cool. There are probably 10-15 places it could be leaking . You can try to isolate where the puddle is underneath or wash the motor and put some fluorescent dye in the radiator . Much easier to find and fix.
I vote for intake gasket leaking to the outside rear behind the motor. It is the hardest to fix because the new gasket never lines up properly. I have seen it more than once.
 
Originally Posted By: mrsilv04
Originally Posted By: Warstud
Remove the plastic cover off the engine and look for puddles of coolant around the intake.


I did pull off the cover and look around the plastic intake.

I did not see any evidence of Dex-Cool around the intake. The intake gasket is seeping a little engine oil (which doesn't surprise me much for a 10 year old car).


That might not be oil around the intake but coolant. Like someone else mentioned the 3.8 manifold leak is more prone to leak outside the engine and around the EGR. Your cap is on the radiator right? How does the Dexcool look inside the radiator. Is it bright orange or something else? A leaky waterpump or heater core is also a possibility.
 
The 2005 L67 in my car had two coolant leaks that I caught.

One was the coolant temperature sensor, which backed itself out of its hole. The wiring harness had a half dozen twists in it!

The other the radiator cap, and it was subtle. It would never leak enough at a single time for even a droplet to appear. But the coolant level would slowly decline over a few weeks. New cap--no more coolant loss. If you still have the TVS cap with the Dexcool sticker, replace it with a Stant. This car can take either a 10230 or a 10231.
 
Originally Posted By: mechanicx
That might not be oil around the intake but coolant. Like someone else mentioned the 3.8 manifold leak is more prone to leak outside the engine and around the EGR. Your cap is on the radiator right? How does the Dexcool look inside the radiator. Is it bright orange or something else? A leaky waterpump or heater core is also a possibility.


No, there's enough of it to be able to tell that it is used motor oil that is around the base of the intake.

There is a cap on the radiator. It is full to the brim and it looks like the Texaco DexCool that I used when I swapped it out last fall. There's no visible sign of contamination of the coolant.

I happen to have a new radiator cap on hand, from NAPA. I plan on putting it on. The one that it on there appears to be a GM OE unit.
 
This is a good point. You do not want the old pressure cap or a defective cap and leaks elsewhere on this system with Dexcool.
 
Originally Posted By: mrsilv04
Originally Posted By: mechanicx
That might not be oil around the intake but coolant. Like someone else mentioned the 3.8 manifold leak is more prone to leak outside the engine and around the EGR. Your cap is on the radiator right? How does the Dexcool look inside the radiator. Is it bright orange or something else? A leaky waterpump or heater core is also a possibility.


No, there's enough of it to be able to tell that it is used motor oil that is around the base of the intake.

There is a cap on the radiator. It is full to the brim and it looks like the Texaco DexCool that I used when I swapped it out last fall. There's no visible sign of contamination of the coolant.

I happen to have a new radiator cap on hand, from NAPA. I plan on putting it on. The one that it on there appears to be a GM OE unit.


OK well sounds like your coolant is good so far now and maybe your cap is working, but might as well try the new cap. Maybe you have a PCV leak, valley leak ,or valve cover leak, but I'm not sure where else oil would be coming from around your intake manifold. You have probably have a coolant leak somewhere. Your reservoir istelf isn't leaking is it?
 
Originally Posted By: mechanicx
Your reservoir istelf isn't leaking is it?


I thought of that as well, once I got back home. It would be a wonderful discovery if I found a big crack on the underside of it.

I'll be unbolting it and checking it thoroughly on Monday as well. And the hose and clamps that link it to the cooling system.
 
mrsilv04 you might want to read this it will help explain the L36 upper and lower intake manifold gasket failure problem.

http://www.pontiacbonnevilleclub.com/forum/viewtopic.php?f=53&t=1061

When the lower intake manifold gaskets start to come apart around the coolant ports coolant is sucked into the adjacent intake port. Sooner or later the gasket will completely fail and dump coolant into the oil.

Coolant can also wick up the lower intake manifold bolts that are directly above the coolant ports and show up as dark pools of fluid on top of the lower aluminum intake manifold.
 
Originally Posted By: chad8
There are many lawsuits over that motor due to bad gasket materials and poor engineering . Contrary to popular beliefs , it is not due to dex-cool. There are probably 10-15 places it could be leaking .
\

What??? it's not "deathcool" Isn't it always the GM V6 engines with the intake gasket leaks. GM 4 cylinders do fine with dexcool.
 
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The GM series II main failure point is the EGR stove pipe. I'd bet that's where your leak is, in addition to the lower intake gasket.

GM 3.8L Fix

Read what member lght1 says. He's the authority on these engines.

Both the EGR stovepipe and the lower intake gaskets WILL fail on these engines.
 
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Originally Posted By: mrsilv04
Originally Posted By: mechanicx
Your reservoir istelf isn't leaking is it?


I thought of that as well, once I got back home. It would be a wonderful discovery if I found a big crack on the underside of it.

I'll be unbolting it and checking it thoroughly on Monday as well. And the hose and clamps that link it to the cooling system.



Welcome to the club. I have a 2000 4.3 that has about a pint disappear every four months on everyday driving. Changed the cap, can't find any leaks, no moisture in the oil or sign of moisture on the oil fill cap, same old story that you see here all the time. From what I've read here the GM dealerships just fill the overflow tank to the right amount and send you on your way (they all do it thing). Now that's kind of odd since they could take you to the bank on repairs. Maybe they don't know as well or just don't want to deal with the PIA real problem. My radiator is clean as can be and fluid looks great.
 
Good info. Here is another person's take, a Delphi guy. No mention of recalibrating the PCM is mentioned. The series III is probably a better fix but is probably not quite as simple to do as the APN. The APN is more than likely good enough.

L36 to L26 UIM swap

Here's a little more info. I don't think I'd plug the LIM coolants ports as one person suggested though:

UIM replacement
 
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