What temperature should I expect for coolant?

[jimbof]

Trying to work out if I should replace any other bits when I get my cam belt and water pump done in 10K miles - like the thermostat or CTS.

 

Looking at channel 45 on the climatronic diagnostic mode while running and up to temperature:

 

70mph, 5th gear ~2100rpm, ambient about 14'C - coolant sensor reading 78'C.

70mph, 4th gear ~3000rpm, ambient about 14'C - coolant sensor reading 74'C.

 

Of course I don't know if the difference above is from the visco fan spinning quicker or the water pump driving it through the rad or the heater matrix.  The highest I ever see at the moment is about 82-83'C, driving at lower speed.   I was under the impression that a value of 87 should be where I should be.

 

What tests could I do to work out if either need replacing without removing them?

 

 

[rotodiesel]

Definitely replace the thermostat with an OE part when you're in there. If you remove the water pump and push the thermostat out from the inside, rather than pulling the cover off, you can avoid breaking the plastic locating tabs in the cover. Fit a new "O" ring - some people also recommend replacing the cover. I've done this job twice now (differing vehicles) and have refitted the cover each time without any leaks. The normal running temperature is about 88 deg C. These thermostats all fail by opening early and staying open for far too long. 

 

Junk from VAG. The French are good at thermostats (pity about the electrical items though).

 

rotodiesel.

[jimbof]

Thanks roto, I'll get it changed when I have the cam belt done.  I am a bit too inexperienced to give the cambelt etc a go myself yet.  If the car still lives in 70K miles more I'll probably do that cam belt as a fun learning experience...!