So recently I went on a weekend trip (about an hour an a half) northward skiing, and when I came back, I began to have problems with the coolant temperature. A few days after coming back, the check engine light came on and the temperature gauge is stuck at zero. When ever I turn off the car, the radiator fan keeps spinning for about ten minutes even though its in the mid thirties here in mass, and when the temp gauge reads zero. Despite this, the engine runs fine, but because the coolant never heats up, the heat doesn't work properly.

 

Not sure what you are asking. If your car is not heating up you need to replace your thermostat. A cold motor will use more gas, not heat the cabin and cause your engine to wear out faster. It may also cause exhaust problems from running rich.

 

Well, my question really is it a thermostat issue or a fan relay problem.

Edit: So I did a bit more research and found that it could also be the ETC sensor going bad.

 

I would suggest checking the temp with a code reader. However, if the car temp gauge says cold, you are getting no heat, the $12 solution would be the thermostat. I can't imagine anything else controling a mechanical thermostat. JM2C.

 

if your gauge doesn't work, and the fan is freaking out, replace both the thermostat and the coolant temp sensor (they are at the same location).

if you feel heat (lots) after driving after you pop the hood, it is actually warming up, how hot is the question, so like above poster, take a scan tool and double check the temp, however it might be really far off depending on if the temp sender -- how broke down it is inside.

A messed up DIM/Gauge cluster could also cause issues.

 

Ok so the weirdest thing happentd the other day while driving: the check engine light went off and the thermostat rose to normal levels. Also, when I shut the car off, the fan wouldnt constantly run. Weird. Anyway, now I have a new problem: the the engine temperature drops all the way on the thermostat while highway driving, then returns to normal when I get off the highway.

 

Replace the thermostat and ECT like stated above and that should fix it right up.

 

Your post gives me the picture that you are low on coolant.

 

sounds almost like an air pocket, but a little backwards, then again air does strange things.

 

I'm thinking' that the above guys are correct. I would replace both the ECT and thermostat and of course at the same time make sure your coolant level is correct. Not a bad thing to do and darned cheap. When replacing the thermostat, make sure you get an OEM thermostat. Many of the aftermarket thermostats out there (trust me I'm an aftermarket counterman/outside sales rep) are not the right choice for you or your ride.