Higher than normal engine temps

[ChkbookMechanic]

The car running hotter, like others have said, seems to be par for the course. However, it still worries me with my '84 being my first Porsche and air-cooled car. So today after driving it around in 100*F weather for lunch I figured I'd better check and make sure the oil cooler was getting oil since the temp gauge hit the 3/4 hot mark.

Being the moron that I am, I reached under the passenger side of the car and touched the oil lines instead of just putting my hand near them to feel the heat. At least I confirmed the thermostat works and does send oil to the oil cooler while getting a reminder to actually look before I put my hand someplace hot.

However, it still makes me want to throw another oil cooler onto my car to help deal with the heat... perhaps project make it project 501 on my list of things to do.

[rusnak]

I'd suggest getting the oil temp gauge with numeric indicators then. It comes with a calibrated temp sensor. The whole project takes less than 2 hrs, and can be done at home.

[burgermeister]

Being air cooled, there is some temperature and engine load that generates enough heat to keep all thermostats open. From this point on, engine temperature will move linearly with air temperature (sort of, humidity and altitude probably have an effect as well) - for the constant air volume to remove the same amount of heat, the temperature difference between the engine and the air must remain the same. Mine runs off the thermostat anywhere above 70 or 75 deg F ambient. From that point on it gets warmer with the air temperature.

My oil temps went up maybe 10 degrees when I switched from the PO's 10W40 to 20W50 oil with my first oil change. Not sure why.

[jonbot]

I can see where all this is going.... Later model Carrera oil cooler with fan... $$$

[jonbot]

Will this work in my car?

FS Mocol 19 row oil cooler kit

[stlrj]

Originally Posted by jonbot

No it hasn't. However, ever since I purchased the car i've been having some off-idle surging. I've worked on the fuel system a little, I got some fuel pressure numbers, and tried paying with the CO adjustment, doesn't seem to help. When I posted the pressure numbers on here a couple months back, I believe it was paulporsche who mentioned that my numbers appeared to indicate that the car runs too rich when cold, and too lean when warm. I'm gonna tinker with the WUR today and see if I can get the pressures back within spec... I got the fire extinguisher ready, wish me luck!

From many years of experience tuning 911s, I can tell you that the most significant influence for oil temps on these engines is timing and mixture. If your mixture is off, particularly in the too rich category, temps will soar as well as having the timing too retarded.

Since you have been having issues with the mixture lately, which tells me that it may not have been dialed in satisfactorily, you may be better off putting your efforts dealing with your mixture before you consider covering up the problem with a Bandaid such as a radiator style oil cooler. All that does is lower your oil temps while allowing your head temps, which you have no way of monitoring, to soar dangerously high with disastrous effects to your valve guides as you drive off thinking all is well.

Originally Posted by burgermeister

My oil temps went up maybe 10 degrees when I switched from the PO's 10W40 to 20W50 oil with my first oil change. Not sure why.

Thinner oil runs cooler because it has less internal friction which is why I prefer 5W30 on my 3.2.


Cheers,

Joe
74 911 w/ 86 3.2 with a trombone cooler only and no temp issues

[jonbot]

stlrj, you are right, my intention is to address the issue, rather than just apply some bandaid, I was just thinking for the future, this might be a good deal, and I could grab it now, and save it for later.

[Bill in OKC]

I have noticed on some other engines (not my Pcar) that they will run hotter when I run the 10% ethanol blended gas. I *think* the o2 sensor cars will adjust somewhat as I have not had the same experience with my truck, but my non-o2 sensor motorcycles don't like what is maybe a leaner mixture from the ethanol.

[stlrj]

Originally Posted by jonbot

... this might be a good deal, and I could grab it now, and save it for later.

I also had thoughts of installing one of these fancy oil coolers, good deal or not, but in retrospect, I'm glad I made the choice of keeping my stock trombone as a way of monitoring my engine temps as an honest indication of what's really going on inside my engine.

I've always had a problem with the the Bandaid approach, that even Porsche uses from time to time, without ever finding out and dealing with the real source of the problem. Why don't we just tune our engines so they inherently run cool and last much longer? Could it have something to do with the confusion over mixture and timing?


Cheers,

Joe

[jonbot]

stlrj, interesting perspective on the topic, one I had not considered, and a good point well taken. I now realize that perhaps the state my car is currently in is raising some unwarranted concerns on my part for the adequacy of the cooling system.

(ie: I'm freaking out!)

[NathanR]

Jonbot,

Don't freak out.

The change you described in the first post of this thread is easily attributable to weather.

If you know you have mixture issues, its time to take a deliberate, methodical approach to resolving them. They may or may not have anything to do with temperatures, but it sounds like they need to be addressed regardless.

FWIW, my car does pretty much the same thing you described when its really hot outside. The way I look at it, if the needle is not pointing at the red line, I'm not going to worry too much. If the factory wanted us to be concerned at above halfway, they would have labeled the gauge red above halfway.


Cheers,
Nathan

[ramonesfreak]

i agree with nathan. mine does the same. i just took a ride, 15 miles, 80 degrees...needle was up past the second white line after only 2 miles. if i compared my 911 to my jeep, i would worry. my jeep is always in the same spot regardless of outside temp. perhaps your using the wrong oil for your environment. its obviously very hot where you live

[jonbot]

meh, we'll see what the shop says next week. I still need to take my infrared gun and point it at the engine and oil lines, who knows, maybe just the sender is bad

[burgermeister]

Are the exterior oil lines before or after the engine-mounted oil cooler?
strlj has a good point - can't hurt to check it out.

Still, my 3.2 does the same thing you describe as well, and it has an external radiator cooler. And the timing can't be off (Motronic, factory original chip), and the mixture shouldn't be either (new O2 and CHT sensors). Not sure the radiator cooler does much if the fan isn't on (and it doesn't come on till 250 deg F or something like that) - it's pretty covered to protect it from rocks and debris and whatnot thrown up by the tire. Next time I have a chance, I'll measure the oil lines right by the cooler and note the difference.

[stlrj]

Originally Posted by burgermeister

...and the mixture shouldn't be either (new O2 and CHT sensors).

Great assumptions but even new 02 and CHT sensors does not assure that the mixture is correct. The air flow meter is the main input used by the DME to determine mixture and the 02 sensor can easily become overwhelmed due to it's design limitations.

Rich running conditions have plagued the 3.2 DME engines from the beginning and are largly responsible for sluggish low end performance issues as well as being implicated as the cause of premature valve guide wear. Perhaps this gave the engineers at Porsche the perfect opportunity to apply the ultimate Bandaid when they installed the radiator style oil cooler for these engines.