Hello All,

I am having a cooling problem that has me stumped. About 3 months ago the car started to heat up more than usual so since then I have replaced the fan with a black magic electric fan, had the timing belt replaced along with tensioners and waterpump, new thermostat, pulled radiator and took it in to be tested, which came back fine, also bypassed the heater valve.
And before you guys start flaming me for the electric fan switch, let me just say that at the time I thought it was my fan clutch and this was a cheaper and faster option.
My problem is actually strange because I have let the car sit in the driveway in the sun for 30 min's and it is fine. But, when I get out on the road it starts to climb after about 15 to 20 min's. It has yet to overheat even after 2 hours of stop and go traffic in 90 degree heat here in Jacksonville today but it does climb close to the 3rd mark. I understand that maybe the electric fan could cause this but all of this is happening with both fans going and not using A/C.
So if anyone has any suggetions, I am all ears.

Thanks,

 

Check the airflow through the condenser. If the condenser is blocked with debris, it will restrict the amount of air going through the radiator. Flowing water with a garden hose from the engine side through the condenser fins (opposite of normal airflow) may push out dust and crap.

 

Crap, I new there was something I forgot to add. Actually Greg, when I had the radiator out I gave both of them a through cleaning and beyond a few small rocks in the condenser coil they were both pretty clean to begin with.
Thanks for the suggestion and keep'em coming.

 

I had the same problem with my '79 Shark. Purchased off of e-bay a factory puller fan set-up from a fellow member (thanks Eric!!). It came off of his '87 S4. I eliminated and removed the front aux. fan, clutch fan, and removed smog pump belt and wired both electric pullers to run constantly at 12 volts. No problems with pull on voltage!! These babies really pull some serious air! The temp never has gotten above the half-way point in the gauge, whereas before, it did the same thing as yours. Also, the A/C will freeze you out now!! That's what worked for me.

 

EBStokes- thanks for the suggestion, I may have to try that if nobody comes up with something else that it could be. How hard and by what means did you attach the S4 fan?
It just seems weird that it would still heat up even after I am going 30-40 mph, becuase from my understanding the fan doesn't really make a big difference after your are in moving.

 

Checked the ignition timing? I once had a car that got hotter the faster you went, seemed to pull ok. Timing was retarded 6Degrees, and thats all it was. Try advancing the timing until you get ping, and see if the temp falls.
Just a thought, as long as there are no symptoms of running lean, which will also lift the temp.
jp 83 Euro S AT

 

Check the rear seal of the T-stat. Not the big o-ring, but the part pressed into the housing. It was the problem on my 87. I got the tip from Erik in Denmark.

 

Actually jp that is something that I haven't thought of, but thats a good point. So, I'm off to check the timing. As far as the car running lean, are there any tell tale signs of this. because the car actually seems to run fine other than a very slight miss at idle.

Thanks for the ideas,

 

Tresamore, you know when I replaced the thermostat I don't remember seeing a seal there. Just to make sure I am thinking of the right seal, this is what the thermostat presses against when it opens, correct? Basically, when you pull the thermostat it is directly across when looking in?

Thanks for the help,

 

Hi,
the engine is designed to operate at/near to 90C
The radiator is actually a heat sink - not like a "normal" cooling system.
You say that it is not "overheating" well it probably won't - considering the oil thermostat does not open until 87C
If the air flow is good etc. then enjoy the fact that the cooling system has a lot of capacity with a OEM thermostat that "cracks" at 83C and is fully operational at 90C. The closer an engine runs its coolant and oil to 90C the greater its life and efficiency - all else being equal
It is possible in some climates that the oil thermostat may be fully open very rarely
The cooling system on the 928 ( both coolant and oil ) has a lot of reserve capacity. Do not judge it against you average car
Regards

 

Hey Doug,

That is good info, all of which I had no idea of. LOL But makes sense once its broken down like that. I am actually basing the overheating on the fact that I purchased my car last year and driving in Vegas 110 degree heat and it never went above the half way point even with the A/C going in stop and go traffic and now it has risen to the 3/4 mark quite a few times and this has been in 60-70 degree weather.
My next step is going to be the thermostat gasket, because of the fact that when I am driving it will go up a little and then back down a little without changing driving conditions, not to mention I didn't know to change or check this when I replaced the thermostat.

Thanks for the information,

 

Yes, its the seal the disk on the back of the t-stat sits against. I never needed to go in there on my 85, but my 87 seal rubber was gone and the steel "skeleton" was there, but it wasn't enough to stop the coolant from bypassing it. I think the 87 and 85 setups are the same. If you get it locally make sure you stress its that rear seal. I don't think it shows in the t-stat diagram, everyone kept trying to sell me the big o-ring. As soon as I got the correct seal and installed it, my temp came right down and stayed there.

 

All electrical gremlins aside...

Anybody know what the marks on the temp gauge correspond to in actual temperature??

 

Hi,
my gauge readings ( base accuracy questionable ) are 80c second mark, 90c third mark.
Read my earlier post on "Oil Condition Report No2". This contains some data on temp. measurements around the engine
The S4's "red" digital highest coolant warning is at 120c
Regards

 

I had the same problem on a 924 a few years back until I discovered the plug to the primary fan was installed backwards. It changed the polarity and the fan ran in reverse. The plug was notched but the receptacle was cracked which allowed it to install either way.

Dennis