Hey y’all, So in my ‘04 Yukon I am noticing that I am losing a small amount of coolant while driving. It holds pressure well so it’s not a leak but I see that it holds some pressure even 10+ hours after driving. I am hoping that it could be something small like a bad Coolant reservoir? Other than that it runs good and doesn’t overheat.
Blown Headgasket?
- Thread starter Woldy1
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- yukon 2500 yukon xl
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Marky Dissod
Full Access Member
One or the other - can't be both. Mutually exclusive. It ain't Schroedinger's cat.
If you have a garage or a regular parking spot, put a very large piece of cardboard on the ground.
The wet spot will point toward where the problem is, but you'll still have detective work to do.
Other thing you can do is apply 15-20 psi of active pressure to the cooling system while the engine is cold, and look for the leak that way. RMI-25 or any other additive that contains dye will make the leak more obvious.
There's a decent chance that some part of the rear auxiliary cooling system could be the culprit.
Look for wet spots in the back ...
cjmcglaughlin
TYF Newbie
If you can’t find an external leak, it could be a head issue, the Castech ones are known for this. The head crack allows coolant into the oil. Could also hopefully be something else like a head gasket, or even an evaporative leak from the radiator or reservoir cap. I’d say try to check your oil for any coolant. Also look at the head casting number (it’s on the front corner of the passenger side head, right under oil fill tube). 706s made by Castech are known to crack. Only way to know for sure it your head is Castech is to pull the rocker arm, as their logo would be underneath. Wish you all the best.
I’m pretty sure it’s the headgasket, I checked oil many times after driving long distances and it looks normal, The reservoir hasn’t ever been replaced.
What is the amount your are losing over what time period?
I was loosing a pint a every few weeks. No leaks on the ground or hoses. Eventually I saw the radiator support was wet under the left radiator tank. It was weeping, but not enough to puddle on the ground. I replaced it and it's been holding rock solid level.
I was loosing a pint a every few weeks. No leaks on the ground or hoses. Eventually I saw the radiator support was wet under the left radiator tank. It was weeping, but not enough to puddle on the ground. I replaced it and it's been holding rock solid level.
drdave81
Full Access Member
Do you get white smoke on start up? Does your exhaust smell sweet? That would tell you if you're getting coolant into the cylinders. It could still be a head gasket, or even the head, depending on where the head cracked. What casting number do you have, 706?
cjmcglaughlin
TYF Newbie
Unless the reservoir itself is causing the leak I’m not sure it would need to be replaced. Like others said, any white smoke or sweet smell?
If you decide to do some testing, buy or rent the tester that will look for combustion gasses in the coolant. Here's one from NAPA, but every decent auto parts store will have one to rent or buy.
Mudsport96
Full Access Member
It could be a myriad of things not necessarily a head gasket. Your best bet it to add a dye and pressure test. There is NOTHING worse than cracking open an engine to fix a nonexistent problem. I learned that lesson young, when I pulled a head for a head gasket that was fine. It ended up being a bad vacuum modulator on the transmission feeding atf up to the passenger side of the intake manifold. So a 20 dollar 10 minute fix turned into 100 dollars and a day and a half.
No smoke, besides vapors cause of cold weather, I’ve had this issue since July 2023. After some more testing I think it might be the radiator.
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