boiling coolant out overflow bottle

[ross41]

My coolant floods out of the overflow bottle, sometimes bubbling and boiling. It's a '94 Laser 1.8L I replaced the thermostat and cap. The car doesn't overheat. I checked compression and it's around 120. If I sqeeze the upper radiator hose mulitple times, it will burp the system and the coolant will go back down and then boil back up.

If it was the water pump, seems like it would overheat. If it was the head gasket, wouldn't I have bad compression? Could it be the exhaust manifold gasket?

Also, the fans do not come on unless I short out the relay with a screwdriver. However, I shorted it out for 20 minutes and let the fans run while I was testing and stuff.

 

[ArticNemesis]

I would lean toward the fact that your compression numbers are under the factory service limit.

http://www.geocities.com/dsmgrrrl/FAQs/compression.htm


Time for a leakdown test to find out where exactly that compression is leaking into. If it's blowing by the headgasket into a coolant passage, that's the reason your coolant is boiling.

Perhaps do another compression test with the water filler cap. Have someone watch the coolant for bubbles while you are doing the test.

A leakdown test will be the definitive answer though.