Higher than normal engine temps
 

I've owned my car for almost a year now, and up until a couple of weeks ago it never ran above the midway point on the oil temp gauge. It would normally sit a little below the half-way point, even during some semi-spirited driving.

A couple of weekends ago I went on a drive with a local Porsche club and was driving the car fairly hard, not probably as hard as I would at a track, but a little bit more than "spirited". During the run I noticed my oil temp creeping up a little past the half way mark, not in to the red, but getting up there, almost half way between the mid point and the red. I figured it was because of the spirited driving, and took it easy for the rest of the drive.

Since then, my engine temps are usually hanging out right at the half-way point, and more often than before, coming up just above the half way point. Any ideas what may have happened? This is my first air-cooled car, on a water cooled engine the first thing I'd suspect is the thermostat, should the same logic apply here?

Next time you take it for a run check the front loop cooler.
It should be hot after temp is up to just below mid way.
If it is not it means your thermostat has quit or you have a kinked oil line from someone jacking the car and hitting one of the lines that runs along the passenger side.
If the loop cooler is hot that I strongly recommend you invest in the "cool collar".
This unbelievable device is unbelievable...honestly.
Did I mention I have one for sale :)
I do but they don't work.

I don't know if "invest" is an accurate word... :D When I was out today I touched the tubing and it was hot, I'm not sure how hot it should be, but it was hot... If for some reason the thermostat was faulty, is it serviceable?

I don't think the thermostat is serviceable but it is replaceable.
If the front loop is hot then it is working.
Nice looking car.
What wheels are on it?

Do some testing. Go to Harbor Freight or Sears and buy one of those infared thermoters and go hunting. Check various places to get an indicaton of what is running hot and where. Is your cooler working? Is your oil quanity proper.

Is there anything in the motor compartment like the sound pad that may have come loose.

It is a long shot but sometimes something can be sucked into the cooling fan, sit on top of the cylinders and create a heat issue.

Is the car running the same. A lean (fuel pump, regulator) condition can make for a hotter motor.

A clogged cat could add back pressure and more heat.

Is it possible the fan belt might be slipping.

Again, a long shots.

Is ambient air temp higher lately, how fresh is your oil and what weight is it, have you changed grades of fuel or spark plug heat ranges?

my hot side oil pipe runs around 190-ish maybe 200, and the cold side about 140-ish or so on a hot day.

You'd be surprised how much hotter the 911 will get on a warm day. Ambient temps above 90 make a huge difference. It got up to 105F today, and very humid. My oil temp at the temp sensor was about 210F. The cat got up to about 400F.

Yes, the ambient air temp today was hot, and also that day I went on the drive with the Porsche group. However, if I go driving in the evening, when the ambient temp drops, the oil temp is still high, it never used to do this. I'm going to do everything you guys suggest, check for loose sound pad, loose fan belt, check for kinks, and use infrared gun. I just don't want my baby running hot, I don't think it's good for her :( I'm thinking it may be good insurance to just spend the 50 bucks and replace the piston in the thermostat, just for good measure, what do you guys think?

I wouldn't touch the thermostat running to the front cooler. That can backfire big time. One thing you can do is adjust the contacts on the heater lever so that it turns on the heater blower while the heater flapper boxes are still open. This will blow cooling air through the heat exchangers.

Hah, that's not a bad idea :D I just got a new dayton blower motor, so maybe I'll try that.

When you mention the idea of replacing the thermostat "backfiring", are you referring to the process of taking the thermostat housing off of the car? Because I would plan on doing it while it's still on the car.

Oh yeah, to answer some of the other questions, I changed my oil 3000 miles ago with Brad Penn 20-50, do you think that could have anything to do with it? I always make sure my oil level is half way on the stick. I am running 91 octane, always have, and no, I haven't changed the temp of the plugs. My cat is gutted, so no clog there.

I'm thinking it may be a good idea to get the temp gauge with the numbers so I can more accurately keep my eye on things.

I just took a closer look at my temp gauge for those tiny numbers written on the side. According to those numbers, and if the gauge is linear, the half-way point between cold and hot is 220*F. The half way point between 220* and 303*(The beginning of red) is 260*. So apparently, my car was running at ~240*F :eek: That's not good, right? We have had some pretty high ambient temps of late, but something must not be working properly in the equation...

an oil change is due and in itself can dramatically lower your temp situation especially if you choose a synthetic, i was really surprised to see how my oil temp was lower totally across the board regardless of outside temp and humidity. best of luck, Bob 83 cab

Another quick note, others had me skeptical of going synthetic over dino, some stating it will cause more leaking issues etc. my mechanic talked me into it and i'm sure glad he did, in speaking with motorcycle owners they also tell me how it lowers their temps as well, i still get the dime size drip i always got no better no worse but it runs so much cooler.

How would that help cool the engine/oil? Cooling the exhaust? Don't see that really helping much if at all.

In fact, don't a lot of racers heat wrap the exhaust headers to keep them hotter so they will flow better? If so, it might be counterproductive.

Just asking the question.


Jonbot, air cooled will run hotter on a hot day, and hotter when you drive it harder (water cooled tend to stay more even temps - that's one reason P went to water cooled, too hard to control emissions w/ big temp fluctuations).

Has the mixture or timing been changed recently?

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! :rolleyes:

I mentioned the external thermostat going to the front cooler. The thermostat body is threaded aluminum, and the threads are known to strip out and stay in the steel oil line nut while the nut is removed. I'd leave it alone unless you are going to change the lines, and even then there are tricks to it.

Racers have headers. If you still have factory heat, then you have heat exchangers, not headers. I don't know about wrapping them to make them hotter and flow better.

I don't have an SC, so I could be wrong on this, but don't some SC owners plug off the ignition advance vacuum in order to get the car to run cooler?

my car seems to be extremely sensitive to the ambient temperature and humidty. when we have a humid 80+ degree day, the temp runs at about the middle point. below 80, its usually in between the first two white lines. if its in the 90's, the temp will crawl past the middle point and then i take it easy on the motor and avoid stop-go traffic.

And when I said "sensitive"...what I mean is : if the engine temp is up a little high because its hot outside, even when I get on the highway and cruise in 5th gear at a conservative speed in order to cool it down, it doesnt cool down.

it appears to me, that the actual temperature of the air has more influence on the engine temperature than the flow of moving air over the motor and oil cooler. this is the opposite of my experience with air-cooled motors. i used to have a harley-davidson that if in traffic, would almost over heat. once cruising at a decent speed, the air passing over the motor and oil-cooler would cool the engine down immediately - not so with the 911, i think for obvious reasons

ive come to believe this is normal with my 911

Scott,

That seems normal to me too. I keep my engine and oil cooler clean in the summer, and keep the oil topped up. Cleaner oil also helps to keep the engine running cooler.

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.

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.

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.

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

Will this work in my car?

http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/419630-fs-mocol-19-row-oil-cooler-kit.html

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.

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

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.

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.

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

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!) :p

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

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

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 :confused:

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.

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.