911 Temperature
 

I have recently purchased my first 911. It is a beautiful 1977 Targa. The car has been owned by a doctor and maintained by the same Porsche mechanic for 20 years. The engine is the factory 2.7L. I got $17,000.00 worth of reciepts with the car. My question is ... what temperature should this car run? I am seeing about 250 degrees not running the AC on a rainey day about 75 degrees outside.

Thanks

That's too hot. I think you should be probably be closer to 210°-220°.

That's way too hot. You'll hear "250 is way too hot" a lot here. It's not a problem if you see it every once in a while, but under certain circumstances it is bad. I hope your gauge is just reading wrong, because if you said the weather was 100 degrees and you saw 250 sitting in traffic it might not be too bad, but at 75 in the rain I would expect to see between 180 and 200.

Your temperature is exceedingly hot for a 75 degree day, just driving around. Your internal thermostat has likely gone bad.

You can do an initial test by getting the engine hot, then reach under and put your hand (carefully) on the internal oil cooler. It should be too hot to touch. You will need to jack up the right rear to reach, and be carefull, there is plenty of oportunity to burn yourself.

You did not mention if the car has an external oil cooler, I assume it does not.

My '77 seems to run around 210 or so at 85 degrees...

Does the car have an external oil cooler in the front passenger-side front fender?

UPDATE:

Well last week I got the car really hot (140) when I felt the trumpet tubes in the passanger front wheelwheel thet were COLD. I called on one of our big suppliers and ordered a External Oil Thermostat (insert). Today I had the car all jacked up and when the part came in, it was a internal engine thermostat. Great news, I was able to take it apart and get the same Thermostat that goes into the external housing. Got it all hooked up, install ed new oil and the car is now running about 210! It is fixed and I did it.

Congrats!

Even without an external oil cooler, this is way too hot. Especially on an average day, like you mention. My car does not have an extenal oil cooler and even on a hot day rarely exceeds 205-210F... and then only briefly. Most of the time it is below 200F.

-MAS

Agreed! I will again suggest testing the internal thermostat.

You also might want to test to make sure your temp guage is accurate.

Other things which you could pursue include:

1) Does the car have a 5-bladed or 11-bladed fan? Mid-year cars fitted with thermal reactors also had 5-bladed fans so the engine WOULD run hotter to meet emission requirements. If so, get an 11-blade fan.

2) Very lean mixture? Ever backfire? Car would run hotter with this condition. Is the timing over advanced?

3) Main thermostat...this opens at 180 degrees to allow hot oil into the main cooler.

4) Auxillary thermostat...found in different places on different cars. Opens scavenge oil retun line to the aux. cooler when return oil reaches 180. If your trumpet is cold and your engine is hot, this thermostat is probably toast.

5) Are the air diverters on top of the engine still intact? These direct air to the vanes/fins on the engine via air from the fan mentioned before.

6) Is the fan belt slipping? Check for about 1/4 inch of slack. If too loose you'll have to remove the nut and adjust your shims to tighten properly.

7) Finally, blockage in the exhaust system could cause overheating.

Ryan