#06-06-01-019B: Information on Gradual Coolant Loss Over Time with No Evidence of Leak Found - (Jun 12, 2007)


Subject: Information on Gradual Coolant Loss Over Time With No Evidence of Leak Found


Models: 2004-2006 Buick Rainier

2001-2006 Cadillac Escalade Models

2001-2006 Chevrolet Avalanche, Blazer, Silverado, Suburban, Tahoe, TrailBlazer Models

2001-2006 GMC Envoy, Jimmy, Sierra, Yukon Models

2001-2004 Oldsmobile Bravada

2005-2006 Saab 9-7X

with 4.8L or 5.3L VORTEC® GEN III, GEN IV V8 Engine (VINs V, T, M, B, Z -- RPOs LR4, LM7, LH6, L33, L59)




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This bulletin is being revised to include engine RPO L59. Please discard Corporate Bulletin Number 06-06-01-019A (Section 06 - Engine/Propulsion System).


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Some vehicles may experience a gradual coolant loss over time. A very low percentage of cylinder head(s) manufactured with an embossed Castech logo may develop a porosity crack in a very specific area.

Inspect the cylinder head assembly to determine if the casting was manufactured by Castech. This can be accomplished by inspecting for their casting logo located on top of the intake port, under the rocker arm support rail and in the spring deck cavity portion of the cylinder head.

Important: If the cylinder head(s) are Not a Castech casting, follow normal diagnostic procedures in SI to determine the cause of the coolant loss.

Refer to the following illustrations on how to identify Castech casting and/or the very specific areas of the cylinder head(s) for a coolant leak from porosity.





Cylinder head(s) location of the Castech manufacturing casting logo (1).





Close up view of the cylinder head(s) showing the Castech manufacturing casting logo (1).





If the cylinder head(s) is a Castech casting (1), inspect the area around the five oil drain holes for witness marks indicating coolant seepage over time (2).

Important: If No evidence of coolant loss is found on inspection of Castech casting cylinder head(s), follow normal diagnostic procedures in SI to determine the cause of the coolant loss.





The crack location can be found in any of the five cylinder head(s) oil drains. This can be seen as a clean or shiny area, on an otherwise stained surface (1). Pressurizing the cooling system at this time may reveal coolant, air, or a combination, weeping in the described area. If inspection reveals evidence of coolant witness marks (1), replace the entire cylinder head(s) assembly.


Here is the bulletin off of Service Information, I work at Hudiburg Chevrolet in Midwest City, ok. This isn't uncommon 95% of the time this is your problem.

 

ive seen quakerstate do that to a couple engines it has a soapy base that sticks to everything when it gets old

 

Don't get yourself scared, that's condensation. You're not losing any coolant right? And you don't see any traces of coolant in the oil? Just take the truck out once every week or two and drive it like you stole it and that should burn it off, if it doesn't burn off, don't worry about it, the moisture is just collecting on the valve covers which may not get hot enough for the H2O to evaporate.

 

he put it back together the oil was pretty clean but the cap on the coolant resivor wouldnt seal and was losing coolant and it just mad them nervous...

 

I like how gmoney states that he was "losing coolant" Im telling you guys those heads are porosed. i did an 04 tahoe last week with the same issue. Sometimes its just one head, but most of the time its both. He can keep changing the oil, but hes gonna keep losing coolant. When his lifters start to tick he'll know the coolant made it there.

 

OP, is the majority of your driving short trip/city driving? The engine needs to get to normal temps and then run for 10 minutes or so that way to let the detergents in the oil clean the internals, and get rid of condensation. You most likely have nothing to worry about.

 

Dang it with all the conflicting answers! lol

When I changed the oil, there wasn't any coolant in it. Is it possible for it to be a cracked head if there's no coolant present?

I had several problems pop up at once, and i don't know how many are related.

1) Coolant loss. Was losing about 1/2 of the reservoir in a weeks worth of driving time. No external leaks. But found that the cap was not sealing to the bottle, so I replaced the bottle with a good one.

2) Smoke at startup. Could this be because of cracked head? I replaced valve stem seals, and all seems well.

3) Condition of valve covers. I thought for sure I had fixed the coolant loss problem until I saw the above stuff underneath the valve covers. Made me think it was a cracked head. I do have the heads that are in the TSB KMAN posted. But none of the oil return holes were washed clean, all were in the same condition.

So, I am not sure what the hell is going on. haha. Drove it pretty hard last night after I got it back together and did not lose any coolant. But only time will tell if it was in fact the overflow bottle, or if it is the heads.

Thanks guys

 

My sister drives the truck and her daily trips consist of:

M-F: Drive to school 20 miles away and then back home. And then to work 8 miles away and back home.

Sits on Saturday mostly, and then driven to church on Sunday 2 miles away.

 

With that amount of driving, you should not have that accumulation of moisture inside the valve covers. Nor the coolant loss. Something is wrong, most likely a bad head or two.

Sorry to give a 'bad news' answer.

 

You're not driving far enough to burn all of the condensation off. I know someone who had the Castech issue on his Avalanche and the issue was much worse than what's pictured.