my gf has a 98 sunfire w the 2.4L motor in it......ok here goes......... we have had the car for about three years, the first year she blew the motor, so i put in a rebuilt motor. i had no problems for about 6 mos. then when we drove the car for a long distance (1000+miles) it over heated on me, i figured ok something broke so i took it to the local mechanic, so i didnt have to try to diagnose the problem my self. he said nothing was wrong with the car he let it run for hours and drove it a few times during the day. So we get the car back from him and it overheats the next day on her way to work, so i just started going through the list of things that it could be. now a year later i have replaced almost everything,

1. thermostat (twice)
2.thermostat housing
3.all hoses
4.water pump
5.radiator and fan
6. overflow tank(nothing to do with it but just to show how much i replaced)

i had a mechanic put a pressure tester on it and it came up ok (no it wasnt leaking and doesnt now but maybe it could help find something) then we had an exhaust gas test done (i dont know what that is but we had it done) we have gone to 4 or 5 different mechanics and asked the opnion of almost every one that i know that is car orentated

HELP ME PLEASE FOR THE LOVE OF GOD I CANT TAKE MUCH MORE!!!!!!

p.s. any thing you think might help will be taken to consideration ideas anyone

thanks

Sorry, this post was origionaly placed in the wrong thred i appologize

Eric, have you thought about bypassing the heater ?

If the problem disappears, it would narrow the culprit.

Sometimes heater core blockage can 'come-and-go'.

i will try that and i will let you know later what happened
thanks, also is there a way to clean out that "blockage" i realy dont want to put any more money into this money pit

Eric, there may be a 'safe' cleaner that you can

run through the entire system and clean that

heater core....

If it was mine, I'd talk to the parts department

at the local GM dealer....

I don't want to guess...

or check for air in the system, any little air bubble would make it overheat hard core.

ok so i bipassed the heater by taking the hose and circulating it with out the heater and it still overheated, and i also have a code on the dash now... i will take it in and see what the code is but any way........i have presureized the system and i thought that would take care of any air bubles in the motor. what else might help any sugestions will help thanks you guys for the help........................

ok i had a problem with overheating for a little while, i would say that it could be leaking in the head or around the water jackets on the head gasket but you said the pressure test came back fine so it leads me to think you need to have your whole system flushed out.. i did this when i rebult my top end, it gets all the trash and rust particles out. the problem with dex-cool which is required in our cars is that the first time it gets overheated it turns into gum inside the water channels in your engine. theres a backflow kit that you can get from autozone, its pretty cheap but believe me it does the trick. pretty much you hook it up to your engine and run a water hose to it and run your engine at the same time and it washes all the gunk and trash out through the radiator filler. its really simple but any blockage in your engine gets pushed out.. check int o that if nothing else.. hope i helped in some way.. good luck man

thanks all, i will try to flush it with the backflow and see what happens

you can still have a blown head gasket.

I have the same problem. 2.4 1997 Z24
I replaced the water pump, radiator, thermostat, temperature sensor, cooling system flush, everything. I was thinking by-passing the heater-core too too, but I didn't think it was.

I also did a pressure test, and compression test. it passed.
no white smoke, or coolant in the oil; the oil looked fine. no leaking coolant ect...

until we finally did a test to see if there was combustion gasses in side the cooling system from the cylinder head.
Test Results: POSITIVE
There was carbone diaxide or whatever its called in side the cooling system.
when there's a head-gasket leak that small its really hard to detect it. unless you run that test.

You really need to do that test, I did mine at Midas.
if its positive, you might have a blown head gasket or the cylinder head might be cracked.