Here's a funky one... my car was running fine until I took it in to the dealer for its 90k. A couple weeks after that, I fry a spark plug and get overheating after driving around for a bit. I change the spark plug and the distributor and the plug wires and the engine runs fine with no overheating for about a week. After that, the same without the blown plug... the temperature actually kind of fluctuates. It will be fine while on the freeway, especially in 4th gear doing about 70-80MPH (around 4-5k RPM). Pull up to a stoplight and the temp just rises to the top line. After putting up with that weirdness for a couple days, I changed the thermostat and obviously drained the coolant (which was only a half gallon) and refilled it (only took about 3/4 gallon). Worked fine for a few days, but now it seems like it burned off about 1/4 gallon of fluid. There is no leak that I can find, but after adding 1/4 gallon of water, I get no overheating problems. Another weird thing is that the radiator fan works on and off. Sometimes it works while the car is overheating, sometimes it doesn't... either way it doesn't seem to change the problem.

I'm thinking that the water pump has gone out. I think this because if the water pump was working, it would be circulating the coolant and the fan would be working on a regular basis. Also, if the coolant just sits in the hot *** engine, the water in the premix will evaporate quicker. I only doubt this theory because I add a little water and the car doesn't overheat, which means that the water pump is circulating fluid. I'd just do this, but I know what a pain in the *** changing the water pump is and I don't want to do it unless I think I have to.

During the 90k they flushed the coolant, but I still saw little white "floaties" in the coolant when I refilled it after changing the thermostat. Do I need to do a proper flushing or replace the radiator?

I'm sick of changing parts and then waiting a few days to see if it fixed it. Does anybody have any ideas?

I just looked up how to change the water pump... what kind of psychopath engineers an engine to have the timing chain turn the water pump??? What a pain...

 

Could be an electrical problem with the actual thermostat plug...its a 2 wire near the back of the transmission, should be green. Also, check the radiator for oil, and oil for coolant. Check all your hoses and when you refill your radiator, make sure you are adding coolant, then squeezing the coolant lines to get all the air out of them.

 

Are you talking about the fan switch (which is on the thermostat housing) or the water temp sensor (which Chilton's says is near the thermostat housing, has a yellow wire, but does not show a diagram)? The coolant did not have any oil in it when I drained it last week, but I have not checked the oil, yet. I'm assuming that if there is coolant in the oil that I have a blown head gasket. I squeezed all of the hoses after adding coolant, and then topped it off after letting it run for a bit. I'll get back after I check the oil. Thanks for the response.

---Josh

 

over heating the way you described it is a sign of a blown head gasket. You might want to check that too.