Coolant overflow after stopping car

[Morrie]

I have spent the last hour doing searches on coolant issues.. still cannot find my exact sutiation so I thought I would post for ideas.

Its an 87 924S, and I have had this problem the past two summers. I have put 10,000 miles on the car since last summer, so I would think that a weak head gasket would have given out. In my quest I have replaced the radiator fan switch and thermostat with low temp units. In cooler weather, the temp regulates consistently at the first mark, between cold and half. It will never climb over half.

When it is hot here in Texas, like now, I run the AC pretty hard in traffic and the car will heat up. If the system isn't bled well, the temp will climb to the 3/4 mark but not all the way to the red.

If I shut it down hot, it will, about 1 out of 3 times, vent its coolant all over the ground.

I have jacked up the left front corner, and bled the system with a pressure bleeder. The cap is a 150 and tests out properly with the tester. The system holds pressure when I pressurize the tank.

The funny thing, and I think MAYBE the problem, is that when I ran the car this evening to open the thermostat and bleed the system again, the system did not seem to pressurize at all. Not with the cap, not with my pressure tester attached. How long before I should start to see the system pressurize?

[zedsn]

I would first try to get a new coolent cap and maybe go up a few extra pounds while you are at it and see if the coolent will stay in then.

[zedsn]

You could also try some water wetter. It will lower your cooling temp.

[Morrie]

I think that trying both would be a good plan. Somewhere to start at least... frustrating because it runs so well but I am gettin real sick of adding coolant and bleeding air. Sooner or later its going to burn up the dang motor.

Morrie

[Aufgeladen944]

Mine was doing this last year; it was air in the system.

However, my head gasket ended up being bad as well, with no other signs of a bad HG like oil in the coolant or vice versa.

Try bleeding it more and see if that helps.

[vdubr928]

Boiling is cause by air at that temp. Bleed

[Rasta Monsta]

Is the overflow tank overfilled? If you filll to MAX when cold, it will piss out coolant when hot. . .fill to MIN instead.