2003 A4 (2.0 petrol) overheating but temperature sensor reading just above 50deg

[bertwibble52]

Hi all,

I am new to the forum and did have a look through but could not find exactly the same symptoms; so I thought it would be best to ask before I start hacking around under the bonnet....

Normally the car drives just fine, with no obvious signs of overheating. However, the temperature sensor more often than not sticks at 50deg, whether in traffic or on the motorway. On occasion it will suddenly jump up and sit nicely at 90deg (where I guess it should be). This has never really given a problem so I have been happy to ignore it.

This weekend we went to Longleat, and driving around the safari park means lots of slow driving. We stopped in one enclosure (thankfully not the lions) when we saw steam coming out of the bonnet. On closer investigation, the steam appeared to be coming out of the expansion tank. The temperature sensor for the entire drive around the park sat at 50deg or just above.

When it had cooled off a bit, I topped up the lost fluid (not very much) and all was fine again.

From reading some of the stuff on the forum, I am guessing I have a problem with the main engine temperature sensor? I also don't think the cooling fan was kicking it, so could I have two issues or is the fan controlled from the main temperature sensor?

Thanks in advance,

Mark

2003 A4 Avant; 2.0 petrol; 110000 miles.

[RickT]

I had an issue with mine a few weeks back, it was the Coolant Temperature Sensor (G2) which was giving a dodgy temp reading... mine was showing hot when it was cold..

Replaced Sensor for £24 + vat and fitted... since then its been fine..

I would start off with that, if the temp sensor is not reading the temp is too hot it wont kit in the fan i would of thought...

Where abouts are you??

See my post below..

Rick



Right... (the above post was a bit rushed..)

The car did it while driving... i stopped... checked coolant etc... set off it did it again...


ANYWAY....

Went out with VAG-COM..

Got the below..

01039 - Coolant Temperature Sensor (G2)
29-00 - Short to Ground

Picture below..

http://i148.photobucket.com/albums/s13/RickT_album/29022008134.jpg

http://i148.photobucket.com/albums/s13/RickT_album/29022008128.jpg

A few weeks back i had to remove this part due to a split hose, it must of been in and out a few times..


-- SO...

I have just "wiggled" it about to ensure the wiring connected is fitted and tested.... Just done 8 miles and its been fine...

Called Audi, part in stock non returnable due to Electrical item. £23.00 + VAT.. --

Im going to go out and do a few more miles this evening to ensure i can test it before purchasing in the morning.. (Lucky im off work all day and i don't go until late Thursday/Friday morning!)

ideally i would like remove it and re-seat it.... but going to test first..

Rick

[bertwibble52]

Thanks for the help Rick, much appreciated. I will try and get this done at the weekend.

Will update my profile, but am in sunny Portishead (near Bristol).

Cheers!

Mark

[RickT]

Thanks for the help Rick, much appreciated. I will try and get this done at the weekend.

Will update my profile, but am in sunny Portishead (near Bristol).

Cheers!

Mark

Hi,

See if you can get someone to read the faults codes on it just to make sure that it is this part at fault..

Take a look at our VAG-COM section and drop a post in there and a member in your area maybe able to help reading the codes for you.

Cheers

Rick

[bertwibble52]

Thanks for the help Rick.

Mark

[bertwibble52]

Update:

I took a flyer and got a new coolant sensor from my local dealer - was £28 including a new O-ring seal.
It was surprisingly easy to change and I now have a working temperature gauge!

Thanks again for the assistance.

Mark

[bertwibble52]

OK....

I now have a working temperature sensor but I now have a question about the cooling fan.

When the engine is cold, the cooling fan now runs at full whack. As soon as the temperature reaches about 60deg it turns off.

If I leave the car idling, the temperature stays at 90deg and the cooling fan occasionally switches on for a brief period - this is what I would expect to happen.

Any ideas why the cooling fan runs flat out when the engine is cold? This time of year I guess it is no problem, but maybe it could be an issue in the depths of winter.

Cheers.