Severe overheating issue - running out of ideas

[Dogbreath]

I have a 1977 Porsche 911S that I recently purchased. The original engine was replaced with a 2.7L engine from a 1974 car (original was a MM disaster) but other than that everything seems original. It has CIS which seems to be functioning properly.

The PO stated that he had been driving the car, but I bought it from a shop where it had been sitting for a few months. The car didn't run when I bought it but I did a few minor things to it and it seems to run fine now.

The problem I have is that it gets hot very quickly. In fact, yesterday I timed it. Granted the ambient was about 85 degrees, but after starting the car and driving it very easy for 5 minutes the oil temp was 210 degrees and after ten minutes it was over 250 degrees. The oil pressure also starts to drop as the temp increases.

I have used an infrared thermometer on various parts of the car while its running hot to confirm the temp gauge is working. For example, if the gauge says 210 I get similar temps on the oil return tubes, the side of the oil cooler and the hard lines going to the cooler.

I have searched the forums and read many threads. I have tried pretty much every suggestion that I found. This is what I have done so far...

Dropped the engine and did the following...

-Replaced the engine thermostat with a tested, working one
-Replaced the temperature sensor
-Replaced the pressure sensor
-Checked the drain plug relative to the sump plate
-Changed the oil with 20w-50 and confirmed proper level
-Took off front sheet metal and checked under the shroud for debris or nests
-Confirmed that shroud cover is secure over the oil cooler
-Sprayed the oil cooler fins with carb cleaner...they seemed to be in good shape and fairly clean.
-Adjusted the valves
-Reset the timing
-Put on a few new hoses, breather cover gasket, sump gasket, oil cooler seals, etc.

Put it all back together started it up and the temp shot right up again.

Here is a little more info and observations...

-There is only one oil cooler on the car...no external or front cooler
-There are no broken head studs
-The car has an after market Bursch muffler and some fairly beat up heat exchangers
-The PO appears to have used silicone in lieu of proper gaskets on sump, breather cover and some other components. I am wondering if some silicone pieces may have found there way into the oil, been sucked up by the pump and into the oil cooler and are now plugging it up.

My questions...since one of the only things I haven't changed is the oil cooler, would it make since to bite the bullet and find a used one that has been cleaned and tested and install it? I am not looking forward to dropping the engine again but may have to.

Would you think there could be any problems with the oil pump itself?

As I mentioned, I am running out of ideas.

Thank you for any advice.

[T77911S]

i dont think you can put the engine T stat in backwords, but i would focus on that and the engine oil cooler.
for it to heat up that fast, oil has to be bypassing the oil cooler or no air flow thru the cooler.
the fins could be clogged up down below the top of it.

even with no external cooler, it should not heat up that fast under normal driving conditions.

[racerboyrt]

How is the mixture set? If the car is way too lean it will run very hot.

[shadowjack1]

Check for a mouse house on the top of the cooler.

[Dan J]

It could well be the scavenge pump is not getting the oil out of the case. Check to see if the sump plate is installed correctly (drain plug on driver side) also take the plate off and check the pick up tube isn't loose or damaged

[bpu699]

You have a laser thermometer?

Use it on the radiator, inline and outline... that will let you know if its cooling. You can even scan parts of the radiator...

If you don't have one, Harbor Freight has them for $20 or so.

Are the thermal reactor things gone? Does it have the newer multiblade fan?

Is it running lean (CIS PLUGGED) from sitting? Check the plugs...

Are you saying the car doesn't have the front thrombone cooler?

Is the temp ok as long as you are moving/speeding?

Need more info...

Bo

[john walker's workshop]

big lower pulley and small upper makes the fan spin faster. SC style. every little bit helps.

[boyt911sc]

Test your auxiliary thermostat in a water bath and watch it slide open @ 186°F. Below this temperature it is fully closed. By 190°F the slide valve is partially opened. Check the other suggestions too.

Tony

[Bob Kontak]

Originally Posted by Dan J

It could well be the scavenge pump is not getting the oil out of the case. Check to see if the sump plate is installed correctly (drain plug on driver side) also take the plate off and check the pick up tube isn't loose or damaged

+ 1

Didn't the guy from the island off of Portugal have the same issue several months ago. He posted pics of his sump plate and it was incorrectly oriented.

Here is the thread with pics of correct orientation - near the end.

Help on SC engine issue, please!

[svaldez]

Sir, Dogbreath...

I highly recommend install an external cooler system. May not be cheap but will solve
your problem.
If it does not than silicone may have entered your oil system.
Just a suggest...since you mentioned not having an external oil cooler system.

[quattrorunner]

Oil coolers are a must in my opinion but I don't think thats your problem.

If you have made sure the sump tube isn't blocked with the drain plug, and the oil cooler is clean and clear for flow of air over the fins, then it must be something internal. Like debris in the oil line inside somewhere?
I don't know.
But I would check with someone with lots of experience here or where you are and be careful with this problem.

[T77911S]

adding oil coolers is a cover up. not the way to do things. even then, you are one oil cooler down.
the oil cooler itself could be plugged internally, a line, but as i said, something with the tstat or cooler area.

[Dogbreath]

Thank you for all your excellent suggestions. I tried a few more things this afternoon.

Pulled the plugs...they look fine not overly dry and white and not overly black and oily.

Tested the temperature going into the oil cooler and coming out with a laser thermometer...great suggestion by the way. It appears that the temperature coming out is quite a bit cooler than going in.

I also took off a WUR that was on a turbo and put my non-working one back on just to see if that made any difference. It didn't within 5-6 minutes of running that car the oil temp was over 210.

To answer a few for the questions asked...

I have the 11 blade fan.
I have a tested and confirmed working thermostat.
I have confirm proper orientation of the sump plate.
I have checked the oil pump pickup and it looked fine.
The are no thermal reactors
CIS appears to be working fine.

I can only image that there may be some blockage somewhere in the engine. It gets so hot so quickly I can't imagine what else it could be.

Thanks again

[quattrorunner]

I'd say remove the cooler and test/clean it and replace.

[Travis Neff]

pull your fan and look for a mouse nest....

[schumicat]

agree, I believe it is doable without removing engine (but much easier with engine out).

I would also verify the oil temp in the tank using a long meat thermometer or a cheap mechanical oil temp gauge ($20 at pep boys), you can lower the gauge probe into the tank.

Originally Posted by quattrorunner

I'd say remove the cooler and test/clean it and replace.

[dtw]

Responders to this thread, please re-read the OP - he's covered most of what you're suggesting. I agree with other posters that an external cooler won't fix this.

250 degrees in 10 minutes - I'd be looking at AFRs and also cooling airflow before looking at the oil circuit. Did you happen to examine the oil that came out? How did it look/smell? How long since it had last been changed?

My bet is on fueling/mixture issues on 30-year-old CIS - bad fuel delivery and/or vacuum issues resulting in lean condition.

Since this is a new-to-you engine, cover some basics to ensure it is healthy and running properly (I'm repeating a couple of things you've already mentioned for completeness' sake):

General engine health
-Perform leakdown and compression check on hot engine
-Perform valve adjustment and check lateral runout of exhaust valve stems
-Check head stud nut torque (set torque wrench to 75-80% of final torque value) (a '74 engine isn't at risk of broken head studs, it is pulled/loose studs that get you on these)
-Put engine on exhaust sniffer or Gunson to verify AFRs

Cooling air flow
-Cylinder cooling tin present and accounted for and installed correctly
-Air guide behind alternator present and accounted for
-Fan belt is in good condition, correctly tensioned, and all 6 fan pulley shims are in place
-No rodent nests under shrouds or in exhaust
-Verify heater valve operation, esp. valves return to 'closed' properly when levers between seats are fully lowered.

Fuel mixture
-Check cold and hot CIS control pressures
-Check spray pattern of all injectors
-Check for vacuum leaks
-Check for smooth operation of plunger in fuel disributor
-Repair vacuum leaks as necessary, including injector o-rings and phenolic blocks, runner boots, throttle body/air metering plate boot, intake gaskets, blow-off valve o-ring and epoxy seal, vacuum lines, etc.
-Check operation of WUR and AAR

[docrodg]

If you find it is silicon clogging the cooler better check the rest... I had plugged cam spray bars thanks to MM that torched the cams and rockers. A front cooler would be a good idea... without extra cooling a 2.7 will heat up fast in our low-speed driving. Another thought... condition of the engine surround. If it is not good then air moving in from underneath fights the air coming off the blower and reduces cooling.

[techman1]

My .02 cents.

Sitting in a shop for 2 months. Possibly for this same reason?

Prior engine was a MM disaster. Possible pieces in the oil cooler from the MM engine!

If your mixture was lean enough to cause this issue, wouldn't his plugs have shown signs of overheating?

[manbridge 74]

I've had three cars with 2.7s and at least some of the cam spray bar holes were clogged on every one. Not sure if it affected temps as it is pretty cool here year round. You can use a small bendable mirror to check after removing valve cover.

Is all heater ducting present left and right of fan?

Can you turn fan easily by hand with engine off?