If it runs OK standing and low speed but cold at high speed only thing that could be wrong is thermostat stuck open.

I guess you didnt read the whole post.

It has a new OEM thermostat and water pump fitted. Thermostat is working perfectly.

Did the fitter test the thermostat in a bucket of hot water before he fitted it in time honoured fashion. New parts can go duff! :rolleyes:

thermostat tested and working correctly +++

Then that only leave the pixies and a sender!:D

Knowing my luck...it'll be the pixies :ROFL:

Engine running cold
 

Do these have a viscous fan cos that can sometimes cause the engine to run cold....the only other thing that ever caused an issue for me was a poorly sealed rocker cover on an old e36....but to be honest the only things that can normally cause it are thermostat or viscous fan

Hello folks! Did you get any further forward with this A8Chick?
I have the same problem.

My 2006 3.0TDI A8 is rather slow to warm up, and never seems to get to 90˚c in fact it seems happier at 60-70˚c.

I replaced the thermostat with a genuine one as I know these are known to stick open, no change.

Next I replaced the G62 coolant temp sensor to no avail.

The Webasto is working fine and I am manually turning it on, but still running cool.

The heaters in the car get warm but not hot like my old passat which suggests it really isn't getting warm, but could be a red herring.

Any tips? TIA.+++

is the fan on all the time or too much? temp sensor for the fan could be making it overcool the system?? :Confused:

I went for a run today was running very cool in this weather.
There is no viscous fan, but there are two well caged and shrouded electric fans and these are both running continuously (abet slowly) from startup, except with the climate control completely off.
VCDS shows that they are being told to run by duty cycle, and the Engine output tests speed them up and down correctly.
Group 7 also shows oil temp and this a few degrees higher as expected but still cold like the coolant.
It would appear that there is only one simplex (two pin grey) coolant temp sensor on this engine.

019 Fan activation\
1) Coolant temperature\
[\'b0C]\
2) Air conditioner fan activation\
[%]\
3) Radiator fan 1 activation\
[%]\
4) Radiator fan 2 activation\
[%]\

http://dl.dropbox.com/u/1273965/fan%20status.PNG