JCP1990S4

I havea a 1990 S4.

Over the weekend I while driving to Vegas I had to shut my A/C off because while I was climing an incline the temp gauge went to the starting line of the red.

Once I shut the A/C off it lowered to the furthest white line to the right.
Note it was 105 degrees outside.

I checked the fans (both working) and the water overflow seemed fine.

My question is this something I should worry about. or is it pretty normal for this car?

WallyP

First suggestion is to check the temp gauge - they are notoriously inaccurate. You can use a non-contact thermometer to check thermostat housing temp, radiator inlet and outlet temp, etc.

A overheated engine feels hot, smells hot.

FredR

If your gauge is correct try the usual fixes- dilute the antifreeze to 33%, throw in a bottle of Redline water wetter and have your radiator cleaned and flushed out if has not been done before or for a long time.

At 105C you are seeing temperatures similar to what we see every day in the Middle East summer season. The 928 stock cooling system struggles and it not unusual to see a stock system hit the redline with the a/c system on.

I run with a big radiator and the above conditions with an upgraded fan system. My needle sits just below the last white line unless I am hammering it in which case it climbs above the last white line.

Regards

Fred R

WallyP

Good to hear from you, Fred!

FredR

Hi Wally,

Have been out of circulation for quite a while- had problems accessing Rennlist for some weird reason so gave up. Also lost all my contact details in a hard drive failure so have been out of touch with many friends. Since meeting many of the UK 928 owners at a UK track day 3 years ago have been posting on a UK based website-nice to pick up our previous dialogue offline if you can send me your e-mail address off line happy to take up where we left off if you still have my e-mail address in your doubtless most efficient style. Trust you are keeping well.

Regards

Fred

Bill Ball

I think uphill in desert heat with the AC on, this is a common problem. I can cruise on level ground in 105 heat with AC on at just under or near the second white line. Hit any significant uphill grade and the capacity of the system to remove heat is exceeded. I do not ever let it get to the edge of the redzone. If I kill the AC, the temp will drop, although not dramatically until I get over the top of the grade after which it will plummet even with the AC on. Also, even at highway speeds, the fans are still critical to airflow. I have had one fan go out, and I'm OK on level ground, but a hill at 60-70MPH is a major strain even with AC off. The stock S4 fans are OK, but I wish we had more powerful fans. The fan control system is rather complex and may not keep up with sudden high demand.

dprantl

It would be nice to be able to have some manual control over the voltage of one/both fans. Doesn't the LH have some input on how fast the fans run?

Dan
'91 928GT S/C 475hp/460lb.ft

FredR

Dan,

The system has a number of protections to cut out the a/c if the water temp or the auto gearbox fluid temps exceed a critical number [cannot remember what it is but it is in the manual].

Louie once told me that the output from the fan controller struggles to put out full system voltage for some reason and suggested wiring directly to the power terminal under the hood via a relay that could be manually engaged if the system is struggling. I also have the twin 12 inch spal fan module fitted- largely because my fan motor bearings were shot and two fan motors were more expensive and less powerful. It will be interesting to see how they stand up but two years on the clock and no problems to date.

With my bigger ally radiator and 30% water/glycol/waterwetter mix the only time I go above the last white line is in summer if I clog it in 2nd [as recently during sharktuning runs].

Regards

Fred