I've got a 02 1.8t GTI and I was driving on the highway the other day and noticed something. My temp gauge started climbing a little so I threw the heat on and it went down to 190 again. As I got closer to work I started to play with it to see if I could determine what caused the problem, I turned the A/C on and the temp gauge started to climb again so I threw the heat back on, nothing was leaking or anything either so could it be the thermostat? If not, what could it be because I need to get this fixed asap. Thanks guys..

 

I know it sounds trivial, but is there the right amount of coolant in the system? How many miles on the car?

 

Without any other information Id say Thermostat

 

What other information are you looking for?

101k on the clock and plenty of coolant running through the system. Just had a line bust and had to replace it so I had to fill up the system with fresh coolant..

 

waterpump

 

has the timing belt/waterpump been changed ever?

If you really want to eliminate the thermostat, take it out and put it in boiling water to confirm it opens.

 

Ok, so my fan isn't working for some reason, how can I go about figuring out if it is the relay or the actual fan motor?

I can drive for a while before the actual temperature goes up, about 5-7miles, because the fan seems to start on initial startup, but not every time. I've just noticed that I can go for a little bit and have the temp stay normal, then it seems to jump around 190 for a bit, goes up and down very slightly opposed to staying on 190. So how can I figure out if it is the relay or the motor in for the fan?

 

you can take a couple of wires and hook the fan directly to the battery. Doesn't matter which terminal (if it's 2 pin), if its reversed the fan will just spin the opposite direction. If it works, it works. If it's 3 pin, I'd imagine one pin for a/c source, one for coolant temp source, and the ground.

 

If the fan works sometimes i'd lean on it being the fan module or a flaky fan switch. Either way if you figure it let me know and i can hook you up on the parts.

 

I've got both fans complete if you end up needing 'em.