Porsche Repair: 911 sc targa porche, trouble with overheating,, oil gauge, temperature gauge

Question
Hi,
I have a 911sc targa porsche 1983, with about 90,000 miles on it.  It has been going on for awhile, but is getting much worse now.  It started out that the engine would be a little past the middle mark on the dash board. then it rapidly got worse, and before i knew it, i cannot drive down the block without it going not into the red, but the top of the line heat.  when it is especially hot it is really bad.
i watch the oil in it, and as I recall, it used to have the sound of a blower fan still on, when the engine  was turned off. i know longer hear that any more. is there a fan that does that? also the fan in the front of the car's trunk is loose.  also some of the belts have some tears and probably needs replacement. can you help?

secondly, all my  head lights on the vechile are not working. ? fuse is ok.  

Answer
Hi Penny,

I'm going to focus on your oil problem and leave the lighting for later. There are two oil issues to be concerned with.  First, Heat.  Second, Pressure.

The air-cooled engines, as you know, are dependent on a belt driven fan to push ambient air through the engine's cooling fins.  Oil in the engine is partly responsible for absorbing and pulloing off some heat, but it's primary role is simply lubication.  The "typical" car uses water and a radiator for cooling.  

The temperature gauge you are referring to is a measure of the engine oil's temperature.  It's not a perfect measure of the "heat" of an engine, but for a street car it's perfectly acceptable.  The ways oil can be overheated deal with loss of the cooling fan's ability to cool the engine...and the oil gauge going higher is a typical result.  This could be as simple as a loose belt.

The other reason the oil could be overheated is low quantity.  Meaning that, for example, if the engine oil level were half of what it should be, a smaller amount of oil would absorb all the heat normally dispersed over a larger quantity.  I realize you said you keep a good eye on the oil level...that's very smart.  The reason I mention this, however, is related to the pressure issue.  If the car's oil level was low, the ability to keep oil pressure within normal operating ranges is much more difficult.  So...that's one important question...have you noticed a change with the "normal" oil pressure readings?  Especially, slightly lower readings at all times?

This pressure issue is potentially troublesome, espcially since you have two oil pumps.  If one failed or is failing, the oil would definitely get warmer AND the pressure would be at lower levels.

As for the fan question, I was able to find a wiring diagram for an '84 model and I do see the presence of an engine fan, and two "additional fans".  Both the fan and the additional fans have their own relays.  So...if you used to hear a fan sound and now you don't, there is every reason to believe the relays are kaput.  If you can id them from your car's fuse/relay chart, I can show you a simple way to test them.

I doubt he oil cooling issue w will not be solved just because we get a fan running again.  I like you to help me understand the sequence of events.  For example, before the heating prblems began, did you have an oil change performed by  someone new to the car?  When was the last oil change and how many miles are on the car?

Write back to me and let me know if you can find those realys.

Dave