Over heating all the time HELP PLEASE!!!

[becca]

alright back in october of last year my car over heated i replaced the thermostat it fixed it until november then it overheated again. so i took it to some mechanic and they said that the head gasket needed to be replaced (almost $800). now about 3 weeks ago it started to overheat again only when i was sitting still. then when i started moving it would cool down. then it got to the point it would overheat going down the road. so hot steam was coming out of my overfill tank. the car shut off on me. so this time i took it to a mitsubishi dealer. they said they ran a pressure test coulndt find anyting leaking, put dye in it and everything. they finally came to a conclusion that it was the overfill tank lid was causing it to over heat. becuase all the antifreeze was going there and staying and wasnt going back through the radiator. so they charged me 200 for a f$&*@ plastic cap. that cost $13. now its overheating again (so of course they didnt fix it). the water is not circulating or something becuase i can put about a gallon of water in the radiator drive for about 100 miles then it starts to over heat again. what is causing this!!! can any one help me please! i cant afford mechanics and i cant afford a new car!! the car has 114,000 miles on and is a 99

 

[wolf20043]

Have you checked to be sure the fan is turning on when the car warms up? It will be the fan on the passenger side of the radiator. (just noticed it is a 420a, so I am unsure of which fan is the rad fan on it though)
Mike
Also, a good tech article:
http://dsmtuners.com/forums/showthread.php?t=200575

 

[femmeDSM]

Cars can overheat for a number of reasons. It's too bad that you found out the hard way (and the expensive way) that throwing parts at it is not always the best way to diagnose the problem

Very basically speaking, though, there are two reasons a car will overheat - It's losing coolant, or the coolant can't get where it needs to go.

Since you have now learned that you aren't losing coolant (are you sure Mitsu actually checked this?), your problem is likely due to a blockage somewhere in the system. Drain and flush your radiator (water will do just fine for this, but if you'd like to, you can purchase one of the commercial "Radiator Flush" solutions out there - Prestone makes a good one).

Also, the link Wolf posted is great - that should be able to answer most of your questions, even if you're N/T