My engine runs hot when I drive it hard. By hard I mean blasting down a back road through 3rd and a bit into 4th but nothing like 100mph or anything. As you drive more legally, however, the temp comes down. Pull up to a stoplight or let it sit still and idle and the fans will never cut off and the car can't cool itself off. It won't overheat, it just won't get any cooler. Stepping on the gas to raise the idle speed will make the gauge go down a bit but then it immediately goes back up when you let off.

The car has a new (rebuilt) waterpump about 14k miles ago, has had 2 thermostats since then, a new radiator, new hoses, and a new expansion tank.

I'm thinking thermostat failure or blockage. When I installed the new expansion tank, I made the mistake of not being able to get it all the way clean. It was a clear tank but I could never get all of some gunk out of it (it was from a wrecked car and the gunk might have been oil or something now that I think about it )

So the expansion tank is a bit filmy looking, but if you look at the coolant itself it's pretty clean.

Paging marky522....ready to do another thermostat?

 

mine does that

 

How high on the gauge does it get?

Before you do another thermostat, bleed it again. Park facing uphill to do it if you can. Could be air in your cooling system.

 

It never gets over the upper white mark, which technically is "acceptable" depending on how much you trust the owner's manual. I figured air, too, especially because I have a very slight heater core leak (although the HCV has been closed for a long time now). Also it was being a bit jumpy. As I am the master of coolant system bleeding from when I used to have a radiator leak, I did that already and it helped stabilize the problem but it still heats up.
It's mainly the fact that it can't cool itself down by idling that worries me. 20 minutes after I had run it hard it was still pretty hot.

 

with fans on, right now, mine gets between 1/2 and 3/4

never past that

and I am happy

still going to do a full tune up on it this winter though

 

mine does this also

 

I had the same issue with my car and fixed the problem by cleaning the grounds. The thing that got me thinking was the gauge moving up and down when I stepped off and on the gas. The grounds on the bellhousing by the back of the engine were dirty and once they were clean the temp gauge operated right and the crazy temp swings were gone.

 

definitely will give that a try. the headlights affect the gauge right now

 

On the track, my 944S2 will climb up to just under the red hash mark. Do audible signs of air in the system, but I suspect a bleeding of my system may help. I have used water wetter but it doesn't help a whole lot.

What has helped was running with the defrost on. Brings the temps down immediately. But it sure gets hot in the passenger area!

My h2o pump is fairly new, as is the thermostat and other related stuff...

-Z-man.

 

I dont run the heat because it puts air in the system due to the heater core leak. i will go clean some grounds and go from there