Radiator caps go bad also. i had a 86 celica years ago and the radiator would leak. and i found out the radiator cap was worn out. radiators caps have a spring and they vent a little after a certain temperature. get the right radiator cap. and definately change the thermostat.

 

its a brand new radiator cap, came with the new radiator. One more thing, can you get air in the system if you over heat. Like I said in an earlier post that when I was practicing my lauches, I overheated, like actually went into the red and over flowed my overflow tank, then forgot to dump the fluid back into my radiator (it never sucked the extra back in).

 

did you flush your cooling system with the heater controls on hot while the ignition was on the ON position with the car not running of coarse, and the top radiator hose off and the thermostat out. you have to put the front of a garden hose in the top of the radiator where the top radiator hose goes and let the cooling system flush out for a good 5 minutes while the water is blasting in the radiator and coming outta the top unconnected radiator hose. you could have your cooling system clogged a little and your themostat should be replaced.

 

no I did not turn the heater on or the ignition, but I did flush the system out for 10 mins. I'll replace the thermostat anyways, it's only $13.

 

do a compression test. then if you want change your head gasket.. when i changed my HG 2 weekends ago, the water sleeves on the gasket were acually rusted and pitted my head and block. the surface dosent leak, but my car was heating up in town and running cool on highway. " it heated up big time under boost" i changed the HG and the temp is normal now..

thermostat 5.00
head gasket " ROL RACING 3mm HG " ask you parts store for a HG for a shaved head and its twice as thick as OEM
price $ 22.50

 

I'm kind of having the same problem... Temp gauge is going up to 3/4, coolant is backing up into the overflow and it's not getting pulled back in. High speed seems ok, it usually heats up at idle.

So far I've replaced the thermostat and radiator cap. Just did the water pump this past weekend, so I don't know if it worked or not yet. I also had the whole system "professionally" flushed about a year ago.

Headgasket is next on my list... Even if it isn't bad.

 

If my HG was starting to go, I know I would see a millly white stuff in my oil, but would I see oil in my radiator fluid too? (like if I took off my rad. cap, would I see oil mixed in?)

 

just because you don't see oil in the rad fluid or visa versa that doesn't mean you don't have a blown headgasket.

http://catalog.thepartsbin.com/?year...mageField.y=14

If you look at the picture of the headgasket, the little holes around the cylinder holes is where the coolant is flowing. The headgasket can blow in between the cylinder walls and the water passage and the oil would have nothing to do with it. So water can leak into the combustion chamber or the compression of the cylinders will force air into the cooling system.

The outer holes of the headgasket are for oil passages and if this part of the gasket is not blown then water/oil will not mix.

My car is doing the same thing as yours, overheats after I've been driving for a while, but only overheats at low speeds. I recently replaced a headgasket so I don't think that's my problem, I'm doing the water pump this weekend and then radiator.

 

why I asked was b/c I thought I saw some oil in mixed in radiator fluid when I took my cap off, but I checked my oil, and didn't see any coolant.

 

Sounds like a big bubble in the cooling system, I have lots of friends who bring cars to me after they do swaps, turbo setups etc etc complaining of overheating. 95% of the time its just bubbles.

Or its a blown headgasket