pits928s

My 1985 928S coolant temperature run high, and too high when in traffic during the warm months. I have replaced the radiator (CSF) and replaced the belt driven fan with an electric fan that comes on when the temp needle exceeds the first white line on the temperature gauge. At highway speeds in 5th my gauge reads above the first white line, not quite halfway to the second white line, which means that my electric fan is running all the time. When I am in traffic my gauge elevates to the second white line and in hot weather exceeds that line. I have also replaced the water pump and thermostat in the last 500 miles. Common sense tells me that airflow through a new radiator at highway speeds should result in enough air flow to not require the fan, but on the other hand the old set up with the belt driven fan provided airflow help all the time, so I am not sure what to conclude. My question is their anything else I should be looking at that could be causing this?

bureau13

Keep in mind that the belt-driven fan had a clutch. It may have been spinning at all times, but it was most certainly not moving the same volume of air at all times. I suspect that your fan clutch was going bad, hence the running hot in traffic. Halfway or less between the white lines sounds about right on the highway, tbh. I don't think those lines are necessarily accurate, just guidelines, but that seems fine. If your fan comes on at the lower white line, then it probably is going to run all the time. Which is not necessarily what you want.

bureau13

I will add that without knowing any details of your electric fan it's impossible to know if it's providing enough air flow in traffic to deal with the heat load. How about your aux fan (pusher on the front of the condenser)? It should come on at some point as the car heats up. If not, you may have a bad temp switch in the radiator.

Mrmerlin

how did you rig the elex fan?
I had a 84 with a 12 inch elex fan the car ran hot in traffic,
once on the freeway it would cool off.
The fan was mounted to the radiator so it was only cooling a small area of the whole core.
If you have an elex fan it would be best to incorporate the fan shroud as well so the effective air movement covers the whole core.
That said,
Buy a new fan clutch for 195.00 and put on a new fan belt,
and you will find that the engine will run as it should,
make sure the aux fan on the front side of the AC condenser is also working.
If not then post back what you see

Speedtoys

So...we had a working design for 30 years, then replaced it..and its not working.


Id suggest putting the stock design back, and worry about it in another 30 years.




Such is the problem with "upgrades" against a problem that never really existed.

DeWolf

I made this sucker using a single 17" fan with a two speed Volvo relay and on high this thing moves some air! With it running on high and the door open you can feel the hot air coming from under the car. And forget not that Porsche went to electric fans in the later cars.

SeanR

You tell us what the gauge reading is but no real details on actual temps. Go get you an IR thermometer and get true readings. I'm betting your car is running just fine and the position of the needle is causing you angst.

bureau13

Certainly an electric fan retrofit CAN work, but it's also pretty easy to come up with a solution that won't. I think a lot of people don't realize the importance of a working fan clutch and immediately blame the belt-driven fan concept as the problem, which it is not. Which reminds me, I have a new fan clutch from Roger that I still need to install....

davek9

OP, do you still have the stock pusher fan in the front for AC & Over temps?
The stock system had two fans, one moving air all the time (more when hot) and one that kicked in when needed (like stop and go).

As for a reference, just above the first white line I read 180/185 from a separate temp sensor installed in the water bridge to an Auto Meter Temp gauge, near 3/4 is around 200.
The stock gauge can vary a bit depending on the connections and age of the sender, like already said, check w/ an IR gun.

Dave K

pits928s

Thank you all for your input. I drove the car a little more over the weekend and found that at higher rpm's the engine would actually cool off down to the first white line. I was at 3000 to 5000rpm going through the gears on some nice twisties rather than chugging along at highway speeds around 2200 in fifth. I'm cooling down by pushing it harder - obviously flowing more coolant through the radiator, but at the same time generating more heat - I'd like to hear thoughtful comments on this behavior.

Another thing I noticed was my A/C condenser looked fairly banged up and I'm sure a bit clogged with road grime - like it was 34 years old with 100K miles on it! Wondering if a new A/C condenser would improve the air flow (and my A/C, which is weak at best), and thus coolant temps in general.

The move to an electric fan from the factory set-up was made after absorbing advice from many sources including this forum. I understand how the viscous belt driven fan works, and it had clearly failed - barely moved at all and the high temps made no difference. I replaced the radiator because it had a minor leak. When I priced this out, upgrading to the electric fan cost less than replacing the fan clutch (I did not find where to get a new fan clutch for anywhere near $195). I decided to do what Porsche did and switched to the electric fan - as they did with their later models - not just because of cost but because it was considered a better solution. Since I am where I am I'd like to try to make this work. I've saved everything just in case we need to switch back. My fan is mounted to the radiator so I see the point behind moving it out to the edge of the fan shroud - so I will make that change if necessary. However, this electric fan moves a lot of air and it runs all the time so I do not think the fan itself is a problem.

I will definitely check the front fan for proper operation at higher temps. Can someone tell me at what temperature that front fan should power up? When I get the IR temp reader I can check this as well as get the other readings recommended. Interestingly, when I started work on the car the front fan was jumpered to run all the time - I had presumed it had to do with someone trying to get the A/C to work. Maybe this was done to address the issue of the higher temps in traffic because the sensor was not kicking it on.

Thanks again!

Pit

Mrmerlin

Roger has brand new fan clutches for $195.00 look up 928sRus.com
Where are you located?
The front fan will come on at 195F
NOTE the updated factory fans include 2 fans with them being mounted off the core of the radiator,
Your belt driven fan will work well with a new fan clutch installed.

NOTE driving in 5th gear at 2K is lugging the engine try keeping the revs up and using a lower gear,
this will also move the more coolant through the cooling system.

Did you also replace the rear Thermostat seal if this isnt done then the system will run hot

WALTSTAR

So what is the actual engine temperature that makes you believe the car is running hot? I have a 84 standard and my temp gauge runs normally just a needles width under the upper white line. Yesterday after a spirited 15 mile run on the thruway, i immediately checked my upper/lower radiator hoses and cylinder heads with my temp gun. I had 183, 152, 196 respectively. Your needle being just around the lower white line causes me to wonder where the needle is and what the actual temps are when you perceive the engine as hot. I removed my AC system years ago and dont have the added interference that you might have with the debris you mentioned. You should surely clean that out.