F451

Hey gang,

Just bought a '83 944 (NA = North American model?), manual tranny. I'm happy as a clam with the 944. My first Porsche. Been lurking here and learning a ton. Great site.

The car has about 65k miles, in good to excellent shape. Car starts and runs fine. Has a re-manufactured water pump put in about a year ago. No idea if they refilled the coolant with the recommended procedure to purge the air.

I have a feeling the PO sold the car when the over heating issue cropped up.

I searched the threads, but thought I would start a new thread anyway.

Problem: over heating under load. Gauge fluctuating between the 3/4 mark and the beginning of the danger mark when running under load at highway speeds, 70 mph or so. No leaks or coolant loss that I can see. Electric fan does not appear to be turning on at all. Gauge needle visibly jumps slightly as it gets hotter and cools down. This seems strange to me, seems like it should move pretty steadily and slowly up and down.

Car seems to be running fine. No loss of power. No knocking.

Should the electric fan be turning on when it gets up past the 3/4 mark? Seems like it should. Would it even do anything at highway speeds?

This weekend I'll be changing the coolant and seeing if I can refill it correctly to make sure its purged of any air. Beyond that, I'm thinking maybe the 23 yr old radiator is plugged.

Are there any ways I can check to confirm that the water pump is in good shape?

How about the rad? Anyway to check that out?

Any and all troubleshooting feedback is greatly apprecaited.

Thanks!

Ed

MyBlackCar

Assuming your thermostat is fine and nothing is clogging your radiator, you either have a hose leak or a head gasket failure. Use a coolant pressure tester to determine if you have a hose leak. Tighten all clamps with a socket wrench.

Check your sparkplugs to see if it is steam cleaned. Do you have white plumes of exhaust and it smells like antifreeze? Regardless, you will have gases (air or exhaust) in your cooling system.

F451

Thanks. No white exhaust plumes at all, and no coolant smells anywhere. Good idea about the pressure tester, I will see if I can get my hands on one. Will also look at the plugs. Hopefully they will be a nice tan/brown color and not all shiny and new looking.

I think the thermostat was replaced with the water pump, but that doesn't mean its not shot. Ok, some good ideas. Keep em coming. Thanks!

ibkevin

Congrats on your new baby!

OK, I always tell people to start in the archives fo rseveral reasons, 1) it helps you word your question correctly and to the problem, 2) you just might actually find your answer, 3) you will definately stumble across accounts of RELATED problems and hopefully solutions that will give you a "bigger picture" of your new rig, and 4) it gives you a good example of the "Renn" atmosphere.

Go with known fixes!! Very important. Take the car out, set the cabin temp to hot, get her up to temp, and vent the coolant bleed screw on top of the block. Take the usual precautions for hot coolant. Check to see if the fans are running and go home. Test the fan switch in the radiator and the fan relay, these are the most likely offenders. Next may be the cooling fan resitors...

You are now well on your way to learning about your new 944.

KuHL 951

As Kevin had stated the archives are full of info. Having an 83 I can say I had the same 'problem' as you. The early cars had a different cooling set-up for the fans to come on and the guages read much higher than the later cars. I don't think your car is overheating at all. I think it does the same continual up/down cycling all the early cars with the 3-blade fans do and it looks scary on the gauge. I got tired of the leafblower fan coming on everytime I stopped at a light and watching the gauge dance. I did a twin 6-blade fan conversion from a later car and have never had an issue in over 2 years now. I didn't even change the fan thermostat. The later fans and shroud are a drop-in and easy to do. The plugs and the right hand rad. hose are different but really don't need to be replaced, just tied back with some Ty-Raps. It is probably the best cheap mod on an early car you can do. Cost me $35 and about an hours time.

Try the bleeding again and see if the highway speed problem is solved first before anything.

F451

Great, thanks for the additional tips guys!

For the archives, I see. I didn't realize that there was a completely seperate archives area. Ok, I am all over that.

F451

Very cool. I will bleed it and see how it behaves.

And its funny that you mention that it might not be overheating at all, because I was wondering the same thing myself. It didn't seem to lose any coolant, and I didn't smell any antifreeze smell at all, nor is it smoking white at all, so it seemed odd to me. Doesn't mean its not overheating, and of course the temp gauge climbing while I did the hill on the highway seems consistent with overheating.

Anyway, I like the sound of that mod and the price is right. I'll do my archive reading, some additional troubleshooting, including the bleeding, and see how it goes. Thanks!

Keithr726

Yup, I have the early 944 cooling "problem" too! How did the six blade conversion go? Any breaking/drilling to make it fit? I'm interested in doing this to my 83.

SoCal Driver

When going to the six blade fans buy a new radiator hose; the one going from the water pump to the bottom of the radiator. The older ones can be hit the tips of the fan blades and worn through. New ones are formed to clear the blades.

Charlotte944

I had a similar issue with my first Porsche, an '84.

To help you isolate the problem do the following:

Get on the highway and settle into a normal cruise at or just below the posted speed limit in 5th gear.
Note the temp gage reading.
Down shift to 4th gear and accelerate to just under 10 over the limit (I use just under 10 over to keep from getting a speeding ticket.).
Note the temp gage reading.
Slow down to the posted limit or your previous cruising speed.
Note the temp gage reading.

Park the car and stop the engine. Note the coolant level in the expansion tank. The normal level is between the Min and Max marks when the engine is hot. Squeeze the radiator hoses. The hoses should be firm but you should be able to compress them slightly.

Let the engine cool and then remove and inspect each spark plug. A "normal" running plug will have orange to light brown or tan deposits. Lean plugs will be bright yellow to white, and rich or fouled plugs will be dark and sooty and may even be wetted by unburned oil or gas. If one plug appeaars to be "cleaner" than other plugs, but does not appear to be running rich, you have a head gasket leak into that cylinder.

While the engine is cool, add enough coolant to the expansion tank to bring the coolant level up to the Min mark. As you drive the car, monitor the coolant level.

If your curise test caused the temp gage to rise sharply under acceleration and then the temp returns to "normal" when you slow down, chances are you have a leaking head gasket. A leaking head gasket will also cause the radiator hoses to be VERY firm when the engine is hot.

With a leaking head gasket you may not see the typical white smoke from the exhaust, but you will see a slow coolant loss with no signs of any external leaks.

Finally, the cooling system is designed to maintain the coolant temperature at a fairly constant level without running the fans when the car is moving above about 35 MPH or so. However, when the car comes to a stop, the temp reading will quickly rise, causing the cooling fans to run. When the fans come on the temp reading should start to drop. If the car remains stopped and left at idle, the fans will cycle on and off and the temp gage will follow. Additionally when the radiator is hot and the ignition is turned off, the driver side fan should run at a slower speed.

Chris_924s

Welcome to Rennlist Ed!
Best of luck with the new addition.

Keithr726

My post earlier was to you, I clicked the wrong quote...oops

KuHL 951

Cliffs advice is right on the money for the original post. He needs to find out why it runs hot at cruising speed first. If he's not losing coolant it might be be an clogged radiator, air in the system, or high coolant/water ratio. The fan conversion I did was to minimize the irritating temp cycling and fan operation of the early cars. I never overheated but it would always get very close in traffic before the high speed fan would kick on. The 6-blade set-up keeps the car in a much narrower temp range now. It is a simple swap and I would recommend getting the fans and shroud as a unit for easier installation. Another plus is they are extremely quiet. No holes to drill or anything. I just tied my wires and hose back with strapping and it works fine. When I do hoses I'll get the new style hose that fits better. Any 86+ car with AC has the twin 6-blade fan set-up so there are plenty around.

F451

Yes, that is the mystery that I need to solve. I haven't driven it under those same conditions since. But for slightly mellower driving on our smaller highways here, it hasn't run as hot as it did that one night. Althought the gauge is all over the place still, just not going up as high/hot overall.

So, need to find out why its doing that first. Once I solve that, I am definitely going to look into the twin fan conversion. It sounds clean, cheap, and effective. A no brainer in my book.

But first things first. I'll be trying to get some time this weekend to check it out. And I'll report back what I find. Thanks again guys!

Ed

ps: I am having SO much fun driving this car!



I can't believe I haven't bought one sooner.

kcryan

not sure if it was said but NA= Natrurally Aspirated, or not a turbo model

Good luck