I am having a problem with my water temp. When i start the car the guage reads cold... as it should. Once its warm it goes half way between Cold and Hot... as it should. i stays like this except the other night i was on the LIE doing like 90 on the way to the DPA races and i am watching the gauge and it starts to drop... but not to hot but to cold. after about a minute i look down and the needle is all the way down on cold , as cold as it can show. when we got off i was at a light that took like 4 min and it started to go back up almost to half way, and then i shut my car off a min later. It happened again to me drving home i was acouple of blocks away and i was doing 0-60 and bringing it to like 5k or 6k rpms in both gears, when i pull in my driveway i see the guage start dropping again to cold. WTF lol. Any ideas? Please help. Thanks guys.

 

air lock/temp sensor/ but most likely the thermostat put a new one in this is the cheapest start to this problem and change the coolant

 

Coolant was just changed. I did it to see. Where is the thermostat located? ( and the air lock and temp sensor lol )

 

there is no air lock sensor as per say run the engine without the coolant cap on till the fan cuts in and keep filling as required, chances are you have air in the system

 

I thought air in the system would spike the temp to hot? My money is on the temp sensor thats directly behind the engine facing upwards.

 

coolant was just replaced? car was ok before that ( I assume ) there for I would be thinking air in the system due to poor quality work

 

no i mean i replaced the coolant after i had this prblem. i changed that whole coolant flange on the back of the engine about 4 months ago. i have a crack in the piping. the sensor on there is still original and where is the thermostat?

 

Faulty temp sender. VWs had this problem quite a bit a few years ago. They do go bad and behave like you described.

 

gaurentee its the G12 ECT sensor.if you got a 1.8t its like a 5 minute job.

 

figured its an easy job since i already changed the piping with that peice... the prob is i think they are lik 80 $ for a stupid blue sensor. thanks very much tho.