928 S4 Engine Temps
 

My 1991 928S4 tends to run at or just below the hash mark between the 170 mark and the 210 mark (red area) which should represent 190 on the engine temp gauge. The electric fans are working and kick on at the 190 mark to bring the temp down to around 180. It has never gone beyond the 190 mark and has never overheated. Is this a normal operating temp for these cars?
Thanks. Chris

Are you checking the obvious (coolant level)? When was the last time you replaced your Thermostat? Are your fans kicking in at all? Not really familiar with the S4, but they have a belt driven fan/clutch set up? If so, when cold does spinning the fan give resistance?

928 Engine temps
 

Yes, my fans are working properly as I stated around 190. Coolant levels are fine. Don't know when thermostat was last changed since I've only owned the car for a little over a year. My question is...is this running temp of 180-190 in the normal range?

Has anyone actually compared the OEM temp gauge with another meter? I'm new to Porsches, but a long time veteran in the Z scene. The 300ZX (both generations) temp gauges are notoriosly inaccurate and a lot of guys end up using a second temp gauge.

My 84S runs in the same area. New OEM thermostat, water pump, recent coolant change, redline water wetter, etc. Stock fan clutch engages well. Aux fan kicks on just before it hits the 2/3 mark then drops down a little. I was planning just to use a different temp switch on the AUX fan. I believe the stock switch is a 92C switch (i.e. 198 F) before kicking in. I'm considering swap it out with a 82C (180F) switch unless I find some reason not to.

That temp sounds just fine.

S4 as I understand it has the fans controlled by the LH brain, and they are dual electric fans. I don't know the normal temp range, but agree on the dash gauge only being a entertainment device, not an instrument. ;) As long as both fans work, come on with AC as well as temp, and the gauge stays in the normal range, I suspect you are ok.

Zdriver, if your front AUX fan is coming on, except with AC, the clutch fan is bad or the radiator clogged. Its not for normal cooling, just a back up to prevent overheating when the clutch fan starts going bad.

928 engine temp
 

Thanks to all for the good info. Now I can worry about something else going wrong.

Thanks for the input. Was planning a radiator upgrade anyway. Maybe that will be my push to get me to do it.

I don't think its the fan clutch. It certainly "feels" engaged and seems to be moving a lot of air. Although I realize that is just an observation.

Simple test, let the motor idle, generally that heats it up.

Does the AUX fan come on without the AC running?

Once the temperature is up, drive at a constant speed between 40 and 60 mph for a mile or so, does the temperature drop and hold at about a fixed point?

Yes, yes means clutch fan is bad, and radiator is ok.
Yes, no means could be radiator and or other parts of the cooling system.

Thanks. Aux fan only comes on sometimes in stop and go traffic - keep in mind I'm in central florida. I'll test it as described. Found a couple of helpful write-ups on rehabbing 928 fan clutches at least to try before buying a replacement.

If you are still trouble shooting this, I just ran across a really good trouble shooting discussion over on Rennlist.

http://forums.rennlist.com/rennforums/928-forum/422773-water-temperature-help.html

One issue that can have an effect on the performance of the cooling system is the rear thermostat seal. Most owners do not know it is there and the rubber part deteriorates.
Worth checking and changing.

That is what is making me crazy, I can't remember if I replaced the rear thermostat seal when I did my thermostat. I suspect I will end up taking it apart to check before summer really kicks in.

928 S4 1987 overheating light comes on
 

Hello,
I am having an issue with my S4 lately... when driving with or without AC on normally the temp gauge is on the second grade... driving uphill it goes up towards the third level and the red warning light comes on even before it reaches the third level.

It never reaches the 4th red level though...

Fans working perfectly, coolant level checked...

would greatly appreciate your opinions