Fluctuating temp gauge

[ScottD3]

Yesterday I drove 4-5 hours to see M-A8.
For first 2 hours of the trip the temp gauge sat at 90 with no issues.

For next 2 hours it would slowly move between he quarter mark and 90 degrees.
I checked the coolant level and that was fine.
There is nothing visual around the car and the engine did not seem to be having issues.

I'll get it scanned to day but in meantime does anyone have ideas or experienced this before?

[Delboy]

The thermostat that is on the gearbox cooling circuit can fail, there is a huge thread about it on audiworld. It would be easy to diagnose if you clamp the hose at the stat and go for a drive

[ScottD3]

Originally Posted by Delboy

The thermostat that is on the gearbox cooling circuit can fail, there is a huge thread about it on audiworld. It would be easy to diagnose if you clamp the hose at the stat and go for a drive

Is it just a normal thermostat that fails?
easy to replace?

[Delboy]

Inline plastic thing, would be easy to replace I would think

[ScottD3]

Thanks Dell.
I'll do a proper search when I'm not using my phone.

If it's easy enough, who's up for doing it at the meet?

[Delboy]

this is the thead that i am talking about, I don't know if your car has the same stat or not but should be simple enough to find out.

Also the diesel are difficult to get up to temp are they not, which is why you need the webasto.

Could there be issues with it?

[snapdragon]

I had that problem too
http://forum.a8parts.co.uk/showpost....9&postcount=39
post 39

[Burnzybubbles]

Originally Posted by Delboy

this is the thead that i am talking about, I don't know if your car has the same stat or not but should be simple enough to find out.

Also the diesel are difficult to get up to temp are they not, which is why you need the webasto.

Could there be issues with it?

Webasto is only needed when the temperature drops to below about 10-7*C, even without The webasto it should reach optimum temp within 5-10 minutes of careful town driving in the freezing cold, once up to temp it should also stay there, if it isn't then there is a problem somewhere, the webasto's are 5Kw iirc so throw some heat out and heat the car up remarkably quickly.





Shame there isn't a secret menu for engine temps on the MMI well not that I'm aware of anyway, all the temp fluctuation will be is either a sender or a thermostat, you will probably have one on the EGR which may be the inline stat that's been mentioned and a main, either way it should be pretty painless to sort out.

edit: after looking at snapdragons post it looks like there's probably 3 then

[Johnmed]

Seems like coolant thermostat to me. Have you ruled out the temperature sender?

On the A2 (3 cyl) TDi these were common failures/easy enough to replace. I replaced mine as a preventative measure, along with the coolant thermostat (that had failed).

I'm guessing on the 8 things aren't quite as simple

[Johnmed]

Originally Posted by snapdragon

I had that problem too
http://forum.a8parts.co.uk/showpost....9&postcount=39
post 39

Great detective work!!!