Even in cold climates the engine should warm up to 190 and stay there. If the gauge is fluctuating then you have a problem somewhere.

If the temperature reading on the dash gauge is acting consistently, always decreasing when the car is in motion, always increasing when at idle at a stop, then you probably have a bad thermostat. It isn't restricting coolant flow any longer and the amount of cooling you are getting is effected by the speed of the water pump (tied to engine rpm). Changing the thermostat by itself isn't too difficult. You can access it from under the car just by removing the discharge elbow (2 bolts) from the water pump housing. The worst part is that the coolant system needs to be drained, which makes the job a bit messy. Given that you have 104K on the car and didn't change the water pump when you did the timing belt, you may still have be running on original coolant, so replacing it wouldn't be a bad thing.

Another possibility is that the coolant temperature sensor in the engine has become intermittent. But then it wouldn't behave in a consistent manor. The temperature reading would come and go when going around turns, or braking, or when the dog barks. The temperature sensor is easy to get to in the AEB, and it will only cost about $15 to replace yourself if you want to try that and see if it solves the problem.

 

That is a most triumphant diagnostic summary. :bowdown: :thumbup:

 

cool, thanks for the info

I will have to find some time to change the thermo sometime this week :thumbup:

 

i'd vagcom log block 4 before you start changing parts. there are two outputs from the sensor...one for the gauge, one for the ECU. vagcom will tell you what the ECU sees. if vagcom and the dash gauge are both in agreement then it's probably the thermostat. if vagcom looks good but the gauge is bad then its the sensor. I'd saythe sensor is a more common failure than the thermostat in this car.

 

you still have it from you t belt kit...you are a brave person...my thermostat and waterpump were fine but switched them out when i got my tb kit to avoid all the work i hope its not that for your sake it would be a shame to take all that stuff off again....

 

Can I ask a question along the same lines of this conversation? I thought that the temp gauge in our cars in not a true temp gauge but just an indicator. What I mean is that it will never show the true temp in the engine and only move when there is a problem. A true temp gauge would fluctuate constantly depending on engine load. My '87 Quantum has a true temp gauge cause it fluctuates a few degrees between the middle all the time. So I agree that you should VAG COM it first to see if there are any codes and see the real temp.

 

^ i understand what your saying.

in my old grand am I could tell everytime the thermostat opened because the gauge would drop.

I'm currently experiencing the same problem as SR and I can say that our car has a true temp gauge because the faster i go on the highway the colder it reads.

When I'm on local streets it reads about 20 degrees hotter than highway, but still below 190 and as soon as I stop, the temp climbs back up to 190.


Jim

 

As above, try the sensor first but be prepared to do the Stat. The sensors seem to give up and the Stat's get lazy. Had to do both on my 98 AEB last year (69K miles now). Bear in mind the ECU does some of its fuel mapping from the coolant temp so you do need to get him sorted.

I.

 

with that kinda mileage, I wouldn't be surprised if the thermostat is stuck open. My brother just bought a 95 subaru impreza with about 70,000 miles on it, and on the trip home from Jersey, down the turn pike, he said the gauge barely moved off of cold, but when they stopped to pay the toll and exit the pike, it moved to normal operating temperature. I told him its most likely his thermostat is stuck open.