Overheating,fans not coming on etc

[Mr.Blonde]

Hi,i had a vag com check and it came up about the coolant temp sensor.so bought a new one and fitted it but it didnt work.The temp gauge didnt move!.So thought it was the thermostat,so after fitting the new thermostat tonight,but when runing the car the gauge still didnt move,so put the old one back in and now the temp gauge works but gets to 85 and doesnt get hotter and then over heats and the fans dont come on!. Could this be down to the temp coolant sensor or just an air block??.....

 

[leshkin]

Check the 30amp fuses on top of the battery - there should be three of these in a small plastic compartment. I had the exact same problem with my old A3 and it was this fuse. For safety they are located close to the battery in order to protect the wiring in the rest of the car.

There are other possible causes of this, but if your temp gauge is working, it's probably not the temp sender that's ********.

 

[adamss24]

How did you bleed the system ? Looks to me that there is an airlock and the thermostat wont open due to the water boiling...as it cannot be pumped by the water pump round the engine.

 

[Mr.Blonde]

Ive just had another go mate and topped up the res tank and kept squeezing the water pipes to pump the air out.The top hose got very hot and lower hose was hot to after a while.The temp got to 85c and has just stuck there for ages!,i took it for a quick drive down the road and it still sits at 85c when i got back.The fans have not cut in and it hasnt over heated??..it seems to drive ok etc perhaps i just need it to run for longer??..

oh am'i right that when driving the temp should sit at 80-85c???..

 

[Broken Byzan]

Driving temp should be 90 degrees once warm. It does sound like you have bled the system correctly now. The fan sensor is on the side of the rad iirc, it would be worth pulling the plug and bridging the circuit to see if the fan will power up manually. If it does, it's the sensor, if not, more likely the fan or relay

 

[Mr.Blonde]

Yeah ill give that ago tomorrow mate,think im just going to get a new temp sensor just for piece of mind.Im sure the fans do work as i never had over heating probelms before this.

 

[Rhod_S3]

I had exactly the same problem. Temp gauge was working fine, the heater was working fine. Saw the temp starting to rise on the gauge, stopped checked coolant level, which was fine, had a look to see if i could see any leaks from any pipes, nothing. Checked the 30amp fuse on top of the battery as suggested by Leshkin and could see that the fan fuse had partially melted and slightly warped. Pulled it out try to clean as best I could the connection and plugged a new 30 amp fuse in and haven't had a problem since. Monitored the temp gauge whilst sitting idle on the drive for about 20mins and could hear the fans kicking in as they should do.

Thanks chaps