Head Gasket Suspected

(Don Franke) #1

Had rebuilt the engine back in 1997 and used Payen head gaskets. Engine had run great and still does, except now have a coolant leak and can not spot exactly where it is. Have a Stant Pressue Tester and with it on the expansion tank pump it up to 10 PSIG get no leaks. Starting the engine with this 10 PSIG the engine will slowly raise to above 16 PSIG at which point the engine is shut down. Allow the system to cool and the gage will remain at 10 PSIG for several days.
Replaced the 16 pound cap on the expansion tank and moved the Stant Gage to the crossover fill. Removed the hose from the expansion tank to the over flow tank and installed a clear 5/16 hose run into a plastic gallon milk bottle. Temperature this day was 50F :Start the engine and in about 3 minutes the coolant was slowly flowing out the hose to the reserve tank line. Shut the engine down as soon as coolant stated coming out clear hose. There is no coolant in the oil and oil level has not changed.
Do I have bad head gasket as I suspect?


(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #2

Hmmmm. If the head gasket was bad, the flow would have begun immediately when the engine was started, wouldn’t it? If it took 3 minutes, it would seem it needed to warm up and start building pressure in the coolant circuit.


(SD Faircloth) #3

Kinda in agreement with Kirby. Should start blowing coolant dang near immediately. And coolant flowing into the atmospheric catchment tank (in the left fender well) is normal when the engine gets hot. When the engine cools down, the coolant gets sucked back into the expansion tank. How much coolant are you loosing ? When is the last time you took off the cover plate at the rear of the left front fender well and examined the plastic catchment tank and hoses ? SD Faircloth


(Robin O'Connor) #4

Just perform a TK test;

1 Like

(Don Franke) #5

Had not seen a significant about of coolant loss. Had added maybe 6 OZ twice the last two times I check the level in the header tank.
Had not removed the wheel well panel to access the catchment tank since the engine rebuild back in 2007. Guess I can do that as a matter of covering all the bases.
Since I could not determine where the leaking was coming from have purchased a new water pump and all new hoses, thermostats and belts.


(Nic Mauduit) #6

You can always do a leak down test, should take less than an hour and if you hear/see bubbles in the coolant circuit you’ll know a head gasket leak is starting to develop (could be between the chamber and the coolant, corrosion bird beaking under the gasket fire ring which could be heat dependant - have the car always had good quality coolant in it?). Or you can wait till it gets worse and more obvious.


(Don Franke) #7

Don’t have a leak down test Gage set up, but think that would be a good tool investment.
Have a small air compressor and from what little I know about doing these test a 125PSI
source should be sufficient.
Doing one cylinder at a time while rotating the engine by using a beaker bar is what should take the most amount of time.


(baxtor) #8

Coolant level needs to be checked at cross pipe cap on the engine. That’s where the coolant is critical and it is possible with a compromised system to have coolant displaced from engine into the expansion tank and not drawn back on cool down leading to tank full engine not so full.
This may well be what is happening at the atmospheric tank end of things.
You may be chasing a problem you don’t have (other than atmospheric tank which belongs in the trash anyway)