this isnt a thirdgen related problem but there are alot of smart guys around here and I like this board anyway.

to the issue- my buddy has a 97 cobra procharged. while running the guage will show higher than it normally does. And its cold out. The cap on the reservoir leaks and spews coolant as it should above 16psi. While hot the coolant tank is full, however when the car is off and allowed to cool for approximately 3 or so minutes the tank emptys itself. New thermostat. new radiator cap.

 

That is what its supposed to do. Hence the name "expansion tank". Notice the cold fill level lower than the hot.
The cap spewing may be due to over filling. If its full cold and needs to expand when hot where else is it going to go.

 

its not full cold though... the tank is completely empty... the tank only fills when the car is hot and running

 

Then there may be an air pocket in the system. Foords many times have a bleed screw that you open when filling the systems. Look around the T-stat. That could be why it pukes the coolant out and when cools takes it all and is not getting enough coolant and more air.

 

Bleed it, if that doesn't work your radiator is shot. When it warms up, feel the radiator everywhere... if some spots are very hot and some are cold; replace it.

 

been there too man.. thats the thing.. its baffeling.. gone through three mechanics and they dont knwo either...

what would be shot in the radiator? just clogged? need flushed maybe? or just dented and blocked? ill check that out thanks

 

Could it be filling the expansion tank as soon as it started? Or even with it hot and good old aluminum expanding. Maybe there is a bad head gasket or somehow combustion chamber gasses getting in the cooling system. Over heated, warped head maybe.
Did these three mechanics do a block test?

 

It might be clogged, I've had the same exact issues on a Z71 though. The radiator was getting warm in "patches" and cold in other spots. I couldn't unclog it so I bought a new one.

 

i suggested a compression test. he is thinking about it. ill have him feel around the radiator

 

He needs a block test more than a compression test. You can get kits at Crapa er I mean Napa.