A4 2.5TDI Q Temp Gauge Not Reading..(2000)

[HAWKS]

Hello.
Ive just bought this A4.Amazing drive compared to my older 1.8T.
Its had a new rad fitted an the temp gauge hasnt work correctly since.(before i bought it)
Also the outside temp on the dash always reads a -figure.
Any clues would be appreciated.

[adamss24]

Thermostat stuck open- common fault on the v6 engines. Require a belt off to change so it won't be cheap...

[PaulF2.5TDi]

As Addams24 said, it'll be your thermostat.
Two of us over on ASN had a work-around that saves you having to dismantle the car and change it here 2.5TDi (and others) Thermostats -there is a link to the other guys fix in my post there.

The OAT sender wil be buggered - you can see it if you look down in front of the radiator behind the bumper.

[Simon.C]

If you can see the date on the sensor that supplies the gauge on the dash, change it if it is over 5 years old. Even if it doesn't fix the problem, it's only a matter of time before an old sensor fails. Replace the o-ring and retainer (if it has one) at the same time.

If the thermostat wasn't changed when the timing belt was last done, whoever did the work can't have been very bright so having the whole job done again might not be a bad idea.

[HAWKS]

Thanks guys.
The fuel pump,New rad and belts were done by a Vag specialist?? i will have to check with them if they ghanged the stat at the same time.
Am i to take it that the Thermostat is in a different place to a 1.8T.

[Simon.C]

This photo stream should give you an idea Audi A6 2.5 TDI - Water pump replacement | Flickr - Photo Sharing!

If the thermostat was replaced, by a VAG specialist, using a genuine part, and if the fault does turn out to be the thermostat, I would press them to repair it for free - genuine parts carry a 2 year guarantee.

It does sound like that radiator job might have disturbed a few other sensors though, so probably best to bottom out those issues first.

I had to have a timing belt replaced early after a previous owner paid for the belt swap but not the thermostat. It's akin to reconditioning a gearbox and leaving a worn out clutch in there.