Ghost Coolant leak on my 04 Yukon XL 5.3... advice anyone?

[Mark-23]

did they pressure check when the engine was hot

They did it both ways

[Mark-23]

^^^ That's a very good possibility.

 

 

If it's not that, my money is on the head gaskets.

 

In the beginning stages of failure, about the only sure-fire 100% accurate diagnosis is with the 4-5 gas analyzer. Test strips MIGHT show it ... but not always. Pump-style CO2 detectors with the blue fluid that turns green sometimes show an inconclusive result. No milky oil, no oily film in the pipe, and no white smoke will be detected in the early stages of failure.

 

If you want to know for sure what you've got going on, you need to grab list of shops within your area, and ask them to do a quick sniff of the coolant overflow bottle with the analyzer, to confirm or deny the presence of HC in the bottle. There's only 1 way HC will get in there. The analyzer will pick up residuals from a shop environment, so over 200ppm HC is the general rule of thumb to go by.

 

And if you have Castech heads that haven't been updated, then I'd put my money on that being the issue, 100%. I believe that can be ruled out by yanking the valve covers and reading the stampings in the head.

 

How do I check if I have castech heads?

[Jsdirt]

Right in this link that txab & 15HDriver posted earlier:

 

 

http://ww2.justanswer.com/uploads/Bluegorilla/2008-12-05_142924_Coolant_loss_5.3.pdf

[Dnt]

Could just be a bad aftermarket water pump? With a real small leak it will evaporate before it even drips when driving along. I would take the mechanics advice and keep it filled up and drive for a while until the leak becomes worse so you can easily identify it. Sealer will only work on a non moving part like a radiator or heater core which you have pretty much eliminated as the problem with your pressure test being good. I would suspect a small leak at the water pump shaft with the engine running only. Water pumps tend to get worse pretty quickly so you will know soon.

[Mark-23]

Right in this link that txab & 15HDriver posted earlier:

 

 

http://ww2.justanswer.com/uploads/Bluegorilla/2008-12-05_142924_Coolant_loss_5.3.pdf

Ok I'll check it out and see what kinda heads I got! Thank you so much!

[Mark-23]

Could just be a bad aftermarket water pump? With a real small leak it will evaporate before it even drips when driving along. I would take the mechanics advice and keep it filled up and drive for a while until the leak becomes worse so you can easily identify it. Sealer will only work on a non moving part like a radiator or heater core which you have pretty much eliminated as the problem with your pressure test being good. I would suspect a small leak at the water pump shaft with the engine running only. Water pumps tend to get worse pretty quickly so you will know soon.

The mechanic was my uncle, he said just keep driving it around till something happens. He said we can't identify anything at the moment because the leak is so small... but he did mention to use a heavy sealer.

 

And that's what he said!!! Exactly like you said it, he's like the leak maybe small but it probably drips and evaporates as you drive so perhaps that is why we don't see anything.

 

He like you got two choices, put in some expensive leakstop or keep driving it till the matter intensifies ect.

[twistoffate]

Might be way too late for my experience but I had same problem....it was a hairline crack in the head. Heat from motor evaporated water from coolant. Left a jelly type congealed form of concentrated coolant in valve covers. If its been going on for months, Pull valve cover & you will know right away if this is the problem.

[Justin101714]

Castech heads very possible! Replaced a bunch of these through the years.

 

 

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