why my M38 radiator won't hold full amount?

alpino · Post by **alpino** » Sun Sep 25, 2011 11:43 pm

The situation is I can only fill my M38s radiator half way. Anymore fluid and it blows out first time I drive it.

"Jeep" people tell me "that it seeks its level" "mine is like that" but nothing curative.

Any ideas? I feel if the truck is supposed to hold the stated/required 11 1/2 quarts, not 6 or so, then there is a problem/inefficiency... and it saddens me to see all that expensive anti-freeze [serious business here in MT] all over the road.

Any advice or repairs? THANKS!!

Post by **wesk** » Mon Sep 26, 2011 12:45 am

Usually coolant being blown out of the radiator while the engine is not overheating is a result of cylinder pressures escaping into the water jacket.

Start with a leak down check of each cylinder. If you are not familiar with this process it is the art of applying about 80 PSI thru one spark plug hole at a time with the piston on BDC and both valves closed. Air heard hissing thru the carb would be a leaking intake valve. Air heard leaking thru the exhaust would be a leaking exhaust valve. And air bubbles in the coolant in the radiator would be a pressure leak to the water jacket.

A coolant pressure test set is also handy if you can buy or borrow one. It is adapted to the radiator filler neck and you apply correct system pressure to it and close the valve and see if the cooling system hold the applied pressure for at least a few minutes. You can also look for any outward traces of coolant leakage while this pressure is applied.

Entrapped air from not properly bleeding the cooling system on fill up can also cause your issue.

A restricted flow radiator issue can also offer up your symptoms.