Stilll Running Too Warm
 

My '89 Carrera began running warm late last summer. It would get to 250f and above. I did the following: Checked the actual temps with an infrared gauge, checked my lines for dents or crimps, checked and cleaned the front cooler, replaced the seal around the cooler, changed the fan thermostat to the one that comes on at 200f, replaced the spring in the external thermostat. All of those things brought the temps down a little, it would climb to around 240f. By then it was time to put the car away for the winter. Beginning this spring I was still plagued with the too warm temps so I had my mechanic check the internal thermostat. Sure enough it was bad. It wasn't beginning to open until 250f. He installed a new OEM thermostat and I then saw temps between 210-220f in 90-100f outside and the a/c on. As the summer has worn on the oil temps seem to be creeping up though the outside temps are moderating. Thursday I picked up a friend and we took a run into SLC, outside temps were in the low 90s and we drove on the freeway at 70-75mph. My oil crept to above 230f. When I dropped my buddy back at his shop I switched the a/c off for the run home into the slightly cooler mountains and the temp dropped to around 220f. Finally, here's the strangest part of this, the oil temps seem to rise the most at freeway speeds when you would think there would be a drop.
When I got home I checked, again, for any obstructions in front of the cooler. None. I noticed the fan didn't come on with the ignition so I started the motor and let it run until the fan kicked on at 220f (checked at the oil sending unit with an infrared gauge). I keep wondering about the fact I have SSIs with one side hooked up to heat (which works fine) and the other open.
Any ideas? My mechanic and I are scratching our heads.
Thanks.

Opening the engine air shrouds to check for animal nests or food caches?

Thanks. The engine was out for a clutch, etc. and didn't run warm prior to that. I had the mechanic check for obstructions when he changed the thermostat.

When your IR reading is 230 where is your gauge needle?

open anything on SSI is not helping to move hot air away...

Has the dash gauge reading stayed consistent when compared to the IR reading?

I have numerical readings on my oil temp gauge which helps with knowing better what the temps are. The needle is halfway between 210 and 250.
Do you think the open right side SSI could have something to do with it? It's connected at the front but open at the rear.

I know this is the obvious one to most... but have you completely eliminated vacuum leaks?

Thanks SS. I can't say there's no vacuum leaks, but there aren't any other symptoms to indicate a vacuum leak. Any ideas as to where the leak would be to cause warmer oil temps?

Not for nothin, remove the alternator and check for debri over the heads, last time I removed my alt, I discovered so much crap in there. I promptly cleaned it out

You stated that It ran hot after a clutch job. I would look at it all from that prospective. Go over the steps for clutch replacement and look for anything out of place. Use a thermometer to check temps IR's are wholly inaccurate when checking temps on metal parts.

just to create thought.
what if the problem isnt the cooling capacity of the car, but the fact it is running way to hot to start with. make sure the car isnt running really lean. at highway rpm it would cause it to run hotter.
have your engine checked for lean condition

This and ignition timing.

Thanks everyone. I've wondered about the mixture and timing. I have a SW custom chip and followed his instructions by putting it on a dyno to look at the AFR numbers and they checked out then. I don't know about the timing. Can they change? I thought they're controlled by the DME and can't be adjusted. Is there another way to check mixture besides a dyno?
Immediately following all the work the temps were okay. Within a week or two I started seeing higher temps, that was finally attributed to the bad internal thermostat. The temps have never been as low as I expected but recently seemed to have crept higher.

I just pulled my dyno sheet and there are two numbers in the AFR section, 14.00 and 15.41, indicated at 4300 rpm. The AFT line was erratic with high spike, SW told me that indicated either a bad coil, distributor cap or intermittent problem with an injector. The cap was new, I replaced the coil and recently had my injectors tested and cleaned. Timing is not checked or indicated on a dyno, how do I check that?
Thanks again guys.

14.00 is a CO of 1.3 but I don't have 15.41 on my chart...that is way lean. I have an SC so am not sure what you run but I'm running a 3.0 (13.38)co at idle (I suspect your first number and generally stay in the mid to high 13.s at speed...it will only spike higher 14/15's when you lift at shift points (onboard afr gauge).
I'd fatten up your CO.....lean will really heat up a 911.
Note. Porsche rec a lower CO for my car but they were concerned with emissions not drivability in the US. Runs better a tad fatter and I run no emissions gear.

Reiver,
Thanks, do I change those number via the chip or is there another way to adjust the mixture?

I've an SC so I can change mine manually (CIS) not sure about your Motronic set up.
I'd say this is part of the problem though as 0.1 co is 14.72 and if you are running at 15.41 you are so lean your computer is also probably retarding your curve to avoid detonation. Retarding your curve also increases heat I've been told (am no expert).
For comparison the factory setting for my car is 1.8-2.0 co and I've bumped that up to 3.0. Runs better that way, less chance of detonation and also cooler for the heads (more fuel= less heat).
Your shop will obviously know how to change the co, give them a call.

Here is a link to some good info. I would start by seeing where your switch is and also check the altitude sensor.

What is the altitude where you are?

911Chips.com - Fuel Quality Switch

Good luck with that deal....I'd get a confirmation on your present CO, only takes a few minutes if they warm the machine up while you are enroute.
Find a shop with a recent calibrated computerized CO machine, I've seen wide variances depending upon the machines state (older analog) nothing wrong with the analogs IF they've been recently calibrated.
Why not try running your stock chip to see what happens?

Im sub'd to this as I have almost the exact same issue. Took the car out of storage this year and noted it running a little warmer than last and at highway speeds, if pushed, I can watch the temp climb.

Harder on the throttle, warmer it gets, go easy it really wont pass 210, but at will I could get it to 240.

Local shop told me to check timing and was sure the car should be dyno'd to tune it better. Could be lean at high rpms!

I'm typically at 4,400-5,200. It's funny because Steve Wong saw my dyno file and thought everything looked okay. I could put the stock chip back in to check temps. I'm leaning (no pun intended) to the too lean theory. Is there a way to adjust the mixture outside of re-programming the chip?