Weird Coolant Issue

[tomloans]

I have a 2003 Tahoe LT. When vehicle is at operating temp and after some driving, the fluid level will drop to a point where my "low Coolant Level" light comes on. Then when I turn off the engine, the level comes slowly right back to the normal middle again. Do I have leak? Anyone have this happen on theirs?

 

[alaska_guy]

I just bought a burb and it also had a leak as well. It's at the mechanics so not sure as I didn't take the time to check myself as he owes me some shop time... However, main cause of coolant loss on these rigs are the following.

throttle body coolant hose leaks
overflow cap not sealing and basically evaporating the water out ($7 for a new cap)
water pump gasket are leaking
old hoses leaking by engine area and or by frame rails if you have rear heat option
oil cooler leaking
Castech head failure (cracked head by oil galley in head)
Head gasket failure.


Good luck!

 

[Doubeleive]

my first guess would be you have air trapped in the system somewhere

 

[swathdiver]

Seems to me the system is open and not building pressure. You can rent or borrow a pressure test kit at the auto parts store to find out.

 

[OR VietVet]

Yep, pressure test and look high and low for any possible coolant loss. Have you done any engine work to it lately? Since you say the coolant level seems to always come back to the SAME SPOT after it cools down I am gonna guess that you likely don't have a leak. I would also check the plumbing between the tank and the radiator for free flow. I am also assuming your temp gauge stays normal.

 

[tomloans]

Thanks guys. I just bought a pressure tester as my other car is losing coolant (slowly) and I cant locate the leak either. I will put it on the tahoe and see if anything is produced on the ground. Of course the greatest fear is head gasket or worse cracked head. The car is not overheating and running perfectly. No smoke whatsoever.

 

[Doubeleive]

Let us know, I'm betting it just needs to be flushed and filled properly

 

[tomloans]

just did the pressure test and immediately it started dripping. I was surprised because while it ran, it leaked so slow I couldn't see the source. But at 15 PSI and cold it started dripping right away. This has been going on for about 3 months.

The leak is coming from the thermostat gasket. Easy fix. So if you have my symptoms look there first. Very slow loss of coolant - unable to locate leak. The pressure tank sinks to 1/4 (low coolant light will come on and off ) then back up to half when you put it in park and with a gradual loss of coolant over weeks.

 

[Doubeleive]

Good you found it, I was under the impression it wasn't leaking and probably just had trapped air.

 

[OR VietVet]

"So if you have my symptoms look there first. Very slow loss of coolant - unable to locate leak. The pressure tank sinks to 1/4 (low coolant light will come on and off ) then back up to half when you put it in park and with a gradual loss of coolant over weeks."

In the OP you never said anything about loss of coolant or having to add coolant. I am glad you found it though.

I guess when I read these posts I am going to have to start assuming some things.