00blackS4

First off, I posted this a while ago and also did a search, but I just want to make sure I'm replacing the right parts since the cost of replacing the thermostat is hugely more expensive than replacing the temp sensor.

I had my temp sensor replaced because the coolant gauge was acting eratically (going from operating temp to cold and then back in a matter of minutes). Now that it's replaced, the needle never moves past the second tick and takes forever to get there. Someone suggested that it might be a thermostat problem, but I'm hesitant to shell out the money if my mechanic botched the coolant temp sensor install or if it's a faulty part. Oil temp is not irregular, the heat works fine, and the coolant gauge is not warming or cooling depending on driving/idling.

Are there any specific symptoms I should be looking for if this is a t-stat problem as opposed to a faulty temp sensor problem?

Sorry to ask again but I'm just trying to get a feel for whether I should replace the t-stat along with the temp sensor.

Casablanca Avant

was done incorrectly you would have coolant blowing all over your engine bay. Though not unlikely I doubt the sensor itself is bad unless of course your mechanic cheated you and never installed the new one. How many miles on your car and has the timing belt job been done, if so at what mileage?

s4net

He has a 2000 tip with 77K. t-belt has not been replaced.
Right now in PA. Temps are about 20F or lower in the morning and it gets up to about 35F during the day.

His gauge will almost get to the bar before the middle (stop and go traffic) but, if he goes down a big hill or is just driving at 60 on the highway the temp goes down to the first bar.
His temp sensor was also replaced but nothing changed.

He then put some cardboard in front of the radiator and the temp stays up much closer to the center. This make me thing it is his t-stat.

s4net

Sorry "Friend" - see above post

00blackS4

The thing that makes me wonder whether it's actually the t-stat is that when I STFA, most t-stat problems are related to the coolant temp needle moves toward the center while idling and then falls back towards 0 during driving. Though my coolant gauge takes forever to move, it stays planted at the second tick no matter how I drive.

Furthermore, when searching, I found a post where a member had a similar problem (i.e. the gauge basically gets stuck at the halfway point) and he noted that his sensor may have been improperly installed. He said before doing the t-stat job, he installed another sesnor and the problem went away.

00blackS4

The gauge does not move to the left or right depending on my driving, which makes me wonder whether or not it's the t-stat or if the new temp sensor was faulty.

berTTos@pjK04

1) coolant temp sensor ($20 part)
2) air in system (bleed + replace coolant)
3) failed cluster
4) failed thermostat ($20 part + crapload of labor)

If you have a vag-com or obdII scanner - get the car up to temp and check what the ecu is reporting for coolant temp. It should be ~185F when the needle is in the middle. If it passes this - then it's likely the cluster.

You can try replacing the coolant sensor again though it's not likely this since it was just replaced. As others have said - I don't see how one could install this incorrectly.

there may be air or blockage in the coolant system. You could try flushing the system.

You could replace thermostat. The part is ridiculously cheap but the labor is huge.


Try the cheap stuff first.

good luck.

BRK

Check out the link..<ul><li><a href="https://forums.audiworld.com/s4/msgs/2705066.phtml">Answer...</a></li></ul>

00blackS4

symptoms that might point to the t-stat being toast.

berTTos@pjK04

if it registers a certain point then never moves then it is not likely the tstat.