Not really sure what this can be. No signs of a leak.

I have 2 videos. Quality is just plain bad but it shows what i need to show.

One shows when it warms up. It is under C and then in a couple of seconds it goes up to norm operating temp.

http://www.youtube.com/watch?v=nq9B5FR-VGg

Second one shows when its at norm operating temp and then goes up slowly. Only seems to heat up at idle. As soon as the temperature goes up i accelerate and then the temperature suddenly goes back to normal.

http://www.youtube.com/watch?v=paE0S3BwTlg

Not sure if this might be a sensor problem. I have never really encountered this kind of problem where the temperature would change so fast.

Any ideas what it can be?

Thermostat or waterpump

There are tests that you can find online to tell you if the temperature sensor is working properly or not.

If I'm reading that second video correctly, the car's not actually moving -- you're revving the engine while parked.

That does suggest it's something to do with coolant circulation. However, it still might be an issue with the temperature gauge sender, which is seperate from the temperature sensor used by the ECU, or the temperature switch on the radiator which controls the cooling fan. Happily that sender is a very cheap and easy replacement, and also easy to test with a multimeter to see if it's still offering the proper resistance.

Usual first step is to check that the coolant level is adequate; with the system cold there should still be coolant in the reservoir (between the LOW and FULL lines marked on the reservoir). Otherwise, the system is sucking air into itself as the coolant temperature drops and the coolant volume falls. If the system is low, fill it up and watch the reservoir's behaviour with the car at operating temperature.

If your radiator cap is not holding adequate pressure, the coolant will boil and you'll lose coolant from the reservoir, which leads to the system getting air into itself when it cools down. That air, plus the bubbles created by boiling coolant, can block coolant flow and in turn lead to more overheating. This might also explain why your temperatures fall when the engine is racing, as the higher engine speed turns the water pump faster, creating more enough flow to force the bubbles to move.

Does the temperature gauge drop when the car is actually moving, but the engine speed is low and constant -- in other words, while cruising? If it does, that tells you the thermostat is probably stuck open. The thermostat should start opening at 80-84C (rated for 82C) and open a full 8 mm at 95C. You can also check the thermostat by comparing the temperature of the upper hose (coolant runs from the engine to the radiator) against the lower hose (coolant runs from the radiator to the engine). If the engine is hot but the lower hose is cold, that tells you the thermostat is closed.

Does the radiator fan kick on when the car is idling and the temperature gauge spikes? If not, check that the fan works by unplugging the temperature fan switch, which forces the fan to run. If the fan runs, check the resistances on the temperature fan switch to see that they're within specifications. The switch is supposed to turn the fan on when the coolant temperature in the radiator reaches 93C, which it does by losing continuity at that temperature.

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Bingo. This is usually the cause of this type of problem. I bet your heater blows cold air when the engine is overheating as well.

Thanks guys. I guess i will check everything step by step.

First i will check if the coolant level is where it should be then i will most likely try to burp all the air out. I read somewhere this is done by warming up the car with the cap off and then turning the heater on?

If not, then good thing the thermostat, sensors, and radiator cap are fairly cheap. Where is the thermostat located in our cars anyway? I have the 2.2 5sfe by the way.

Yes this was done while i was parked and revving the engine. Yes it stays at normal operating temp while cruising. Have not really paid attention to the fans. When are they suppose to turn on?

I just hope its not the water pump.

A $10 multimeter can save you hundreds of dollars in parts. Check the sensors before you go about replacing them.

The thermostat is cheap, but you also have to replace the coolant lost from disconnecting the return hose. The thermostat is inside the metal section of the return hose, against the engine.

Lagos, thank you for remembering the heater temperature. I knew I was forgetting something.

Bleeding the cooling system is done with the radiator cap off and the cabin heat on, which forces out any bubbles trapped in the heater core. Keep topping up the radiator as the bubbles rise to the radiator neck or you'll just introduce more air into the system. Preferably, have the front of the car slightly elevated to encourage the air to exit, though that's not absolutely necessary.

I let the overflow tank get rid of any bubbles, thats what its there for.

All you have to do is start the engine and let it heat up. The coolant expands and pushes all the air out the radiator cap, through the overflow hose and into the overflow tank. When the car cools it will pull coolant back into the radiator instead of air.

This post has been edited by Special_Edy: Nov 17, 2012 - 7:45 AM

Topped off the coolant (ALMOST A WHOLE GALON) and did that process to take out the air. Though much air did not come out as i didnt have to add a lot of coolant once i turned on the heater.

Seems to have solved the problem. I guess i must have a leak somewhere since i knew i topped it off when i purchased the car about a month and a half ago.

One thing i did notice. The fan next to the battery turned on as soon as i turned on the ignition and stayed on the whole time. While the other fan never turned on. When is that fan suppose to turn on?

I believe that's supposed to be the A/C fan, for the A/C condensor.

Fan next to the battery is the cooling system fan. The fan next to that is for the AC system. If the cooling system fan runs all the time, the coolant temperature switch (the sensor which activates the fan) is probably shot.

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That works, but bleeding the system with cap off is much quicker and with greater assurance you won't over- or underfill the reservoir.

I have a similar problem. Took it to a mechanic and he showed me with the infrared thermometer(while the needle was high) that my car isn't overheating. He said I probably have a grounding issue with my thermo sensor(gauge). I don't remember but he shot at the engine block, thermostat, and radiator. The reading came out to be around 168? I think. Been too long. I've been driving my car like that for at least 5 months now. Drove it a couple hours and the needle is up high but not in the red zone. I know it's a risky take but I spent too much money trying to fix this. Not planning on spending even more. Buying a multimeter is highly recommended. If I would've bought that in the first place. I could've saved myself from buying all the sensors I bought hoping it'll fix the problem. If my engine does eventually overheat. I'm hoping I can engine swap it with an upgrade. Either a 1MZ or the 3SGE.