Coolant Temperature Guage

[filipharvey]

Picked my 1.8T A6 up today.

It was fine for about 10-15 miles, and then the temperature went up to about 110 degrees. If I dropped my speed to about 40, it would then drop back down again.

At slow speeds (road, not necessarily engine) it seems fine, but go faster and it creeps up.

Any ideas on what it could be?

Temp sensor?
Thermostat?
Water pump?

 

[Issac Hunt]

Water pump sounds possible, although the other two are common on the 1.8T.

If its overheating though that sounds the water is not being circulated - pointing to the water pump possibly?

 

[filipharvey]

It never goes hotter than 110 and always drops back down to 90 when I slow down.

When the car was stationary and I turned the ignition on , the gauge showed 90 then crept up to about 105 without me even starting the engine. Turned it of and on again and it showed 90???

I haven't had the opportunity to do this when the engine is running as of yet though.

When stationary with the engine running, water seems to be pumping back to the expansion tank ok.

 

[Issac Hunt]

Try a temp sender first then, thats the cheapest and quickest thing to change.

 

[filipharvey]

You don't know whereabouts that is on the 1.8T do you? Also will one from a A4 1.8 (NA) fit as I know the one from my A4 of that engine is ok?

 

[Issac Hunt]

I couldnt say for sure but I imagine they 'might' be the same.

There is a guide on the forum smewhere for changing one (on an A3 though I think)

 

[filipharvey]

I've looked at the back of the (NA) 1.8 engine and there are 2 sensors connected to the water pipes, I'm guessing the blue one is the one I'm after?

 

[Issac Hunt]

I think so, yes.

 

[filipharvey]

Ok, well I'll try that 1st, then the 'stat, then water pump!

 

[filipharvey]

Just took it out for a drive to check it.

Was fine on the trip into town of only a few miles, crept up when nearly back home.

I opened up the bonnet and the turbo was glowing and both fans were running. I only stopped for a few seconds and by the time I got back in the car, the temp had dropped from 110 to 90 again!!!