Ok i seem to have an issue with my temp gauge. While returning home from edinburgh today i noticed my temp gauge was playing up. 8 miles from my house there is a long steep hill as i was going down the hill my temp gauge fell to just under the 90c mark as i reached the bottom of the hill and accelerated the gauge went back up to bang in the middle 90c.

Thought it was a bit weird as the whole way home (145 miles) the gauge was as it always is at bang in the middle at 90c it never moves from there after the car is up to temp just seemed to drop slightly while going down this steep hill.

Now i have replaced my CTS last year for a the green newer version and also i got that from the dealers so i hardly think that could be playing up. I was thinking it could be the thermostat starting to play up but surely if that was sticking open the car wouldn't get up to temp and stay there it literally stays at 90c the whole time bar this one off today. I have also replaced the Rad switch aswell last year. Any ideas welcomed.

cheers

Just keep an eye on it as there may be nothing wrong. I've experienced similar when coasting downhill before.

Sounds like the symptoms of my thermostat when it went, temp dropping on the mway and went up in traffic.

Could be getting old.

A sticky thermostat would just mean the car could take a long longer to get up to temp (if stuck open). Can you get vagcom on the CTS to see if the outputs from the CTS look sensible?

Ill keep an eye on it this is the first time its done it, I was coasting down the hill for at least 3miles as soon as I hit the throttle it went back up to 90c weird though I was coasting down hills on other parts of the journey just seemed to happen on this longer steeper one.

How easy is it to change the thermostat on these engines? Is there a thermostat housing that gets replaced aswell at the same time? reason I ask is I changed a thermostat on my corrado when I had it and also had to replace the housing.

Cheers

I don't have access to vagcom mate, I only have one of the cheap ebay code readers, forgot to say that I scanned the car using that when I got home and didn't come up with any faults.

I wouldn't worry about it. Like you said, 3 miles and no throttle, the engine will naturally cool down, especially in the cool weather we're in now.

If the thermostat was stuck open, it would never get to temp.