Awhile back, I started overheating. Just to test a theory, I took the thermostat out to see if it ran cooler without it in, thinking that I needed a new one. It ran excellent. However, unfortunately, I started running the car without it for longer than I should have, which shouldn't have caused any real damage. Well, I finally bought a new one, popped it back in, and started overheating again. Took it back out, haven't had one since.

It's been running fine without it, minus the fact I have no heat. However, the last two days, I started overheating again. The needle on my guage doesn't show a gradual rise in tempurature though, instead it fluxuates up and down constantly. When I accelerate it will go down a few notches, then back up, then back down, etc. What the hell could this be? I was thinking about replacing my water pump and timing belt, but I don't want to do that if that's not really the problem.

 

Do you have any leaks? Check the coolant levels. Also do you have any smoke comming from the exhaust? Have you noticed whether or not the fan is kicking on?

 

I don't have any leaks, the damn thing took two gallons of coolant and water in the past two days, and the fans are kicking on. No smoke from the exhaust, either.

 

Well if your adding coolant and the are no leaks I'm gonna lead torwards a blown headgasket. Try doing a compression test.

 

I'll check it out, thanks. =]

 

Here's the thing about not having a thermostat. The thermostat regulates the temp, as you most likely already know. Without it, temp fluctuations or spikes are common, especially if there are extreme temp changes within the sections of coolant.

One thing comes to mind is the coolant temp sensor, it could be caked with corrosion and just needs to be changed out. These are inexpensive and easy enough to change out.

With winter coming, a thermostat would benefit your motor in terms of fuel use. The ECU will dump in fuel if it's cold out because the air coming in will be more dense and the colder motor temp won't help. The other downside to not having a thermostat is that the motor will stay cool unless you drive it for awhile, thus hindering motor performance. So, you can see why it's important for you motor to warm up.

Removing the thermostat is just a band aide, there's something else that is causing your motor to overheat. It could be as simple as a bad coolant temp sensor. I'd change that out and put the thermostat back in and go from there. Afterwards, I suggest flushing out the radiator, motor, passages, and putting in new coolant. The coolant is supposed to be flushed and replaced after so many thousands of miles anyway. So, give that a shot and get back with us about this issue.

 

Ooops, forgot to mention the radiator.
Are the fins on the front of it all bent? When was the last time you took a hose to it (with hose nozzle of course, you need some pressure to do this) and sprayed out the dead bugs, dirt build up, or even road grime? How much of the radiator surface has bent fins and how much of the radiator surface is usable? If it has 50% or more of the fins bent, you need a new one...or you can try to straighten the fins with tweezers. If you have the average amount of fins bent (10-15%), then go elsewhere in the cooling system for resolution to this issue.