SC Running Really hot
 

So with the summer heat coming I need to solve this problem that I've ignored during the winter.

My '82 SC with 139K miles runs hot. Engine is bone stock.

After about 30-60 minutes of 80mph cruising in 80+ degree heat, the temp guage registers between the upper white hash mark and the red zone (10:30, if the guage were a clock). Let me know if I need to post a pic of the guage.

On even hotter days and longer drives it reaches the bottom of the red zone (11 o'clock). This has to be bad. During the cold weather, it has run in the normal temp zone (9 o'clock)

Data:
- The oil lines and trombone cooler are really hot to the touch.
- Only one small dent in the line, and in my non-expert opinion can't be having a material impact - or can it? You tell me. Can post pic if needed.
- Have installed the oil cooler scoop in the marker light
- I run 20/50 non-synthetic Castrol and yes, the level is up.
- The fan belt is tight. Is there a tension/free-play test to check it?
- When I did the plug wires I was lazy and did not use the rubber wire routers that plug into the shroud. So there are 3 or 4 small holes in the shroud where the routers should be. Would this have a material impact?
- The part number on the fan/shroud is 930.XXX.XXX. Does this mean a PO upgraded to a turbo fan?


Should I bite the bullet and try the oil thermostat ? (yuk, PITA)

I've heard an old/bad catalytic converter can make it run hot. Would that be bullet #2 to bite? Car seems to have good power, so it doesn't drive like the exhaust is clogged, but I also wouldn't know what it *should* feel like. It's my first 911.

Other ideas, from this crowd of experts?

Wow, that IS hot for only 80+ degrees and at cruising speed...and at colder temps I NEVER see even close to 9:00, even stuck in traffic. I'd check the fins and engine area completely (PITA, but behind the fan, too) to make sure you don't have debris (or a mouse's den) stuffed up in the crevices. Then maybe check that you're not running too lean. Once you find the problem, it may be worth it to you to get a cooler (Jared Fenton mentioned in another thread he found a Euro 28-row cheap ...might be a poss for you). Hope this helps. Post back your findings ...I'm curious, anyway. :)

Edward

Yup, something is seriously wrong. Under those conditions my SC never gets off the white mark.
Either the oil isn't flowing as it should, or it is getting too hot in the first place. Is your engine running extra lean?
I think I'd pull a spark plug or two and see what they look like, if its running lean that would make it run hotter.
A useaful tool is an infra-red temperature gun. You could map out the temperatures to make sure you have a temperature drop across the lines to the trombone cooler.

Do you park the car where critters could get to it and move in? I have seen mice set up camp on top of the cylinders - not good - but you can usually smell that.

Any chance it is running lean?

My bet is a thermostat.

George

My engine before rebuild had this problem. It was a non functional engine thermostat.

Just too hot. I would not drive it that hot becuse if you encounter some traffic during your ride it could really hurt the engine... however, no panic yet, it could be as simple as a faulty sender or temp. gage, thermostat... Go by elimination until you get to the real problem.

BTDT, this was the problem. Use a pyrometer on the oil lines, or better yet on the temp sensor to verify your gauge readings. You were running between 250-300 degrees. :eek:

Thanks for all the ideas.

Can't wait to get home, open the Bentley book and start poking around.

It is likely the on-engine thermostat. Test by carefully reaching under the on-engine cooler and touching it. It should be too hot to keep your hand on it. Watch out for the exhuast.

Could it be that old problem with some SC's: cavitation in the oil pickup? This is cured by installation of an updated engine drain plate that includes a reformed strainer screen, which sacrifices the drain plug (I think). This problem usually happens at high RPM and is accompanied by loss of oil pressure.

Howard

The oil-pick-up problem was with 78 and 79s. I would check behind the alternator as others have suggested. Also the gauge itself to see if it's reading correctly and matched with the sender.

How long have you had the car and did it run cool before? My 78 before the major rebuild ran hot. When we tore it down we saw the engine oil cooler was coated and clogged from an oil leak. Might be something for you to look at while you are investigating the thermostat.

Check the accurancy of your gauge & sender.

did this just suddenly start? Make sure your timing is not too advanced. Is your WUR OK?

problem found...


- The oil lines and >>>>>trombone cooler<<<<< are really hot to the touch.


euro 28 rows are cheap!

but if it was fine before... my guess is the t-stat.

That's hot! If all is well with the engine, the trombone should keep this thing cool unless you're driving the pi$$ out it. Check the internal cooler to see it's circulating oil. If so, before you put in an additional cooler, find the problem.

I suspect if you richen and retard, you'll see a difference. Check your timing and make sure you're not too far advanced. Then if you haven't had your mixture checked do so or, just richen by an 1/16 - 1/8 of a turn.

__

I don't see that as a problem. The oil lines going to the trombone cooler should be hot after a long drive. That's an indication the thermostat is openning.

I'd venture to guess that the trombone cooler and lines shouldn't be hotter than 210 or so under those conditions.
Upgrading to a better cooler would be a band-aid in this case, trying to treat the symptom and not the disease.

There is two thermostats on your car. The one to the trombone needs to open, but also the one letting the oil go to oil cooler on the engine. That thermostat is located on top of the engine case in the front.

George

"The oil lines and trombone cooler are really hot to the touch. "


then at least that T-stat is working...

I still think your gauge / sender combo is the first thing you should investigate. These commonly go out of callibration. Drive to a shop & get them to measure actual oil temp.

Had the car for a year and a half (Nov '03), started mid last summer. But that was the first summer I owned it so......

Will check everything, including engine oil cooler. Stupid confession #378: Didn't know the thing had an on engine cooler.

Also, funny that Paul mentioned the WUR. I do have an idle hunt problem and occassional full-on bog on when starting from a standstill first thing in morning. Problem is gone within minutes of first firing engine. sammyg2 is setting me up with a WUR. This problem did not exist winter of '03-'04 only just this past winter.

Lots of ideas to keep me busy this weekend.

Bump to catch opinions of the weekenders

i gotta agree with the baseliner opinions already listed..confirm the accuracy of the temperature gauge..have a shop set proper timing and mixture to eliminate those factors. if trombone is hot, then aux thermostat which leads to the aux cooler (trombone) is functioning..i believe this is supposed to happen at about 170-180 degrees. next time it's hot, check the temperature (hot to touch?) of the ENGINE oil cooler (not the trombone) and see if it's hot as it should be.

i agree that your cruise temps at those ambient and driving conditions should put you near the top of the normal operating range, which is generally 180-220 for these air-cooled motors without aux oil coolers, thus your normal range should be maybe 10-20 degrees lower. good luck and let us know what happens.
ryan

last year I had high temp problems - my engine mounted oil cooler was gunked up by some past oil leak. so I pulled the alternator/fan out, used carb cleaner, followed by simple green, and a garden hose pushed all the way back. all kinds of black pieces and cottonwood tree fluff balls came flowing out. now my temps are back down to normal.

I know that it is difficult and very subjective to determine if you are too lean or too rich so looking at your gas mileage might be a good indication of where your mixture is.

Cheers,

Joe

again, if you aren't much of a diy'er, have a shop set proper timing, idle and mixture (they have the gas analyzer you need, unless you're familiar with estimating by duty cycle). this won't cost a fortune and will nicely baseline your car. new plugs, cap and rotor..points if you use them..are a good idea too.
ryan

Update:

-Timing, idle, and mixture set. It was a little lean.
-Cat was beginning to clog, so it's gone.
-The shop worked on the on engine cooler - apparently it was a mess. But a PITA to R&R and clean without dropping the motor so lots of degreaser sprayed in. It's a little better, so that thermo may be OK, but too much oil and goop on that cooler seems to be the culprit. The cam seals were just replaced due to oil leaks - would that impact the on engine cooler?
- Will check all fuel pressures next time in for AC fix and see if I need a WUR too.

Any secrets to R&R the on engine cooler without dropping the motor?

Thanks everyone for all the input.

Put a Piragua in the engine compartment to it cool down.

I always thought excessively retarded timing causes excessive heat. i had the timing retarded when installing a new distributor on a chevy smallblock and saw the headers glowing red.

After a run, all the headers glows red. Drive your Porsche at night and see the headers glowing.

If the car is running to lean, what MPG numbers would he be getting?

-I think 20ish around town and mid to high 20's (running 70-75mph) on the highway is normal??

I have been getting around 23mpg highway with a 70-80 mph average.

Hypothetically, I crossed 100 coupla times last night without adverse temp impact. Dare I say it ran cooler at 100 than it has been at 80? But its just a hypothesis. I never exceed the posted limits.

I'd love to see that mileage on my SC. I get high teens around town and about 20mpg on the freeway. I've seen as low as 16mpg. That was when the car was new to me and I couldn't keep my foot on the accelerator nor the smile off my face. :-)

Interesting,

I don't have any temp issues, and I just tuned the car, which has never run particularlly lean. I've got 140k miles or so on mine, and I get about 20 around town, and 25-27 on the highway-if I'm staying at a steady 70ish..., fast running over say 85, and I get about 20 even..

-Adam

Changed to synthetic a couple of weeks ago.
Before 23.2mpg
After 25.7mpg.

do you guys only drive downhill? If I'm lucky I get 15mpg. On long freeway shots I might get up to 18 or 19....maybe. Typical is about 14mpg.

Maybe its my driving style :p

btw, the trombone cooler was fine at keeping my car relativley cool even in 100degree temps in SoCal...at least on the street. It was *not* sufficient for track use in those ambient temps.

I agree on the cooler bit, if it's clean and set up correctly it works pretty well-at least on the street..

-I'm told that sc's prior to 81 get a bit lower mpg than the later year cars, I've only had an 83 so I don't have personal experience but my concern has always been not to run too lean because of the related problems with that...I remember a guy a few years back in the 914 club that was bragging that he was getting mid to high 30's on the highway, problem was he was running lean as hell and killed his motor..