Coolant system

1999 Camaro V6 125K miles. Occasionally overheats. No noticeable coolant leak. Was pressure tested and passed. Mechanic suggested new radiator cap. New cap installed and was fine for a while then overheated again and problem seems to have intensified. Any suggestions please. Will a compression test reveal anything regarding this problem?

Not a compression test. But instead a leak-down test will. A leak-down test involves removing a spark plug and in it’s place a special adapter is threaded in so an air hose can be connected. Then that cylinder is brought to top-dead-center. Then a constant supply of compressed air is injected into the cylinder. Then you look in the radiator at the coolant to see if any air bubbles form. If any do, it’s an indication of a breached head gasket.


Thanks Tester
I was suspect of intake manifold head gasket leak but hoped for an easier fix. Wouldn’t the leak be visible though just by making a close inspection? This sounds like big ticket item…any idea what this would cost to have it fixed?

crystal clear