Here's the problem: i have '99 supercharged dx hatch: I have 68,000 miles on the stock motor(over 40,000 of those miles are supercharged.) I keep overheating. Here is what happens.
For some reason.....my radiator keeps emptying antifreeze into my resivour. I will fill the radiator to the top and then fill the resivour to the Low level. After about 50-70 minutes of driving ....my car will begin to overheat, because the radiator will keep dumping antifreeze even over the High Level in the resivour(cannister). I have replaced my single core stock radiator with an OEM style Dual Core Del Sol Radiator. I have replaced all of my coolant and I have also replaced the thermostat. When I did the thermostat....i noticed the electrical connector to the thermostat housing was loose.....so I tightened it. I disconnected my battery and the problem still persists.
My old boss who owns a shop says that the problem is a head gasket. However, my oil is clean, my plugs are dry, and I am not seeing any clouds of smoke from my exhaust. WHAT IS WRONG WITH MY CAR!!!! I just keep putting the overflow back into my radiatir when it is low. PLEASE HELP!!!!!

 

uhhhh.... anyone???

 

I tend to agree with the mechanic that it's probably burning out of the HG. Maybe it's only happening under WOT or hard load, and that's why you can't see it?

Run a comp test, then a leakdown and post the results. It has to be going somewhere, and if it's not on the ground, it's got to be burning.

FYI, the dual core Del Sol rad is an awesome upgrade, and should be more than sufficient for your setup.

 

Do a comp check and verify that your radiator fan is not dead.

Sonny

 

When cars get very hot the coolant reservoir tends to fill up.

Is your fan coming on?

 

I'm gonna agree with the mechanic as well, a blown HG could leak exhaust gas into the coolant passages and blow the water out especially under load. Your coolant/oil doesn't always have to mix, you don't always have to blow smoke out the back, and a compression test won't always show bad results. Do a leakdown test and or pull the head and see whats up.