91 Protege DX overheating...

My '91 323 is really pissing me off. It recently began to overheat. The state inspection said the reason was the water pump. It needed fixing anyway, so I replaced that, and now the car is overheating even worse than before. My radiator cap seal was shot, so I got a new one, but it doesn't seem to help. I'm thinking it's the thermostat. Any suggestions?

Does it overheat all the time at both high and low speeds? Does the engine run ok? A thermostat regulates the minimum temperature and normally will not cause overheating unless it sticks in the closed position. Most will open when they fail. Are you having to add any coolant? I assume your water pump belt is tight. If you can find someone with a cooling system pressure checker it's a good idea to run a cooling system pressure check to check for any external or internal leaks. It's difficult to tell what may be your problem without some additional information. Do you know if the radiator is original. One other check you should do is to run a compression check on each cylinder.

I didn't mention the cooling fans. It should be obvious if they running when the car is overheating. If they are not fix the fans before spending any more time replacing other cooling systems parts.

Clifton

It just overheats at high speeds. I can drive around town all day at normal slow speeds, but I take it up to 55 for a while and the temperature goes up. I just replaced the coolant and haven't had to add any more. The engine itself runs fine, except the timing got way off when I replaced the water pump. The radiator looks original, and the cooling fans run fine. I also ran a compression check and each cylinder is fine. I still can't figure it out.

You mentioned the timing was wrong after the water pump was changed. Has the timing problem been corrected? I assume you refer to camshaft timing. If the cam/valve timing is too far out it can cause the engine to overheat but it should also have some effect on how the engine performs. If the timing error hasn't been corrected it's a good idea to get it corrected. But, based on your original post you replaced the water pump hoping it was causing your engine to overheat. Water pumps usually don't cause overheating problems. Their usual problems are leaks or noisy bearings. I know a ratiator is expensive but it sounds like it could be your problem. At hiway speeds the engine generates considerably more heat than lows speeds and a partially clogged radiator cannot provide enough cooling capacity to keep the engine cool. If your radiator fins are clogged with road trash and bugs you should clean the radiator fins by using a water hose in the rear fins to flush out the bugs and trash. If cleaning the fins doesn't help and you have a good radiator shop in your area I would talk to them about having the radiator flow tested. I'm not sure if they can do the test with the radiator in the car. If the flow isn't adequate you need a new radiator. Most recent radiators aren't economically repairable so it's usually best to buy a new replacement. Hope this information helps.

Clifton

Right. Thanks for the help, dude. I guess I need a new radiator.

I guess not. I just replaced the thermostat and now the car is back to normal. Radiator was fine.

Good to hear the thermostat was the problem. Sometimes our guesses are wrong so it's best to eliminate the cheap possiblities first.

Clifton