What are the signs of a bad coolant tank cap in 1998 ford contour lx?

tdiatlanta

Cap seems to be dead and coolant dissapears slowly with no leaking.

Mr_Shiftright

Usually there would be some staining around the cap, as it would leak out around the seal. Coolant is lost either through a visible leak or through burning in the engine. There is no other way for it to disappear.

If you still loose coolant after replacing the coolant tank cap, then do a pressure test on the system and look for external leaks, or (worse) pull the spark plugs and look for coolant on them while the system is still under pressure.

You can also use a simple chemical test to detect combustion gases in the coolant itself. Not all head gasket problems show water in the engine oil.