Over Heating 911 3.0

[GLASEM]

Looked through the thread but did not find any prior postings that seemed to relate

Have a 1977 911 with an 1983 3.0. Replaced the trombone cooler with a Mocal in the right front fender. Never any over heating or oil pressure issues.

Recently having over heating (275 area) and lower than normal oil pressure (20-35psi) when on the freeway. After cooling off and running on the street it stays right around 170-200 in temperature and great oil pressure.

Just started in the last week. Both times from the freeway use.....nursed it home. Once I got onto surface streets.....oil temp cam down and oil pressure came up.

Do I have an oil thermostat issue? If so.....which one????

[lindy 911]

I don't think you have an oil related issue. I'd check for a mouse nest or two under the fan shroud on top of the cylinders. Look up under the car with a good flashlight through the cylinder cooling fins and see if there is anything blocking the air flow. Next check the color of the exhaust outlet. It should be a light to medium grey color. Anything towards white suggests that the CIS is running lean and will heat up the motor.

Lindy

[Vincent Hill]

Originally Posted by lindy 911

I don't think you have an oil related issue. I'd check for a mouse nest or two under the fan shroud on top of the cylinders. Look up under the car with a good flashlight through the cylinder cooling fins and see if there is anything blocking the air flow. Next check the color of the exhaust outlet. It should be a light to medium grey color. Anything towards white suggests that the CIS is running lean and will heat up the motor.

Lindy

I was expecting ALL kinds of answers but not this one and it is a Good one. Also the Lean or retarded makes them heat up also! I will tell you one thing, If that mouse decided to stick it out for the ride, it is an Over Done mouse now!

[GLASEM]

Checked to make sure that a mouse was not an issue.
Pulled the alternator out last week to inspect under the sheet metal.

Did not see any mouse or any type of debris.
Did see the typical oil/sludge build up....nothing that should cause overheating.

[schumicat]

feel the mocal cooler to see if it is getting warm. if not the external thermostat (by right rear wheel well) isn't opening. but even without the front cooler you shouldn't overheat, barring extreme driving conditions (track session or driving up a mountain in summer). there is also a thermostat on the engine for the small engine-mounted cooler. I would confirm gauge is accurate; I did this by buying a cheap mechanical temp gauge ($17 at Pep Boys) and lowering the sender into the oil tank.

[DohertyCM]

I would agree with the last post....Intermittant means there is a problem somewhere....but the mouse thing would seem to be a constant problem, not intermitant... A thermostat problem is what i would look at first. Not that looking for a mouse is a bad thing...because you should look at all of the air passages and oil cooling spots.

[Vincent Hill]

To check for Lean, FInd a "Friendly" Garage and ask them how much to put a "Sniffer" in your exhaust? If they will do it for $50 or less, check Idle and slowly rev the engine up to 3K RPM and hold it for a second and see what the reading is. Anything above 16 to 1 is lean and below 12 to 1 is rich. I do not know what A/F a Porsche runs to be perfect but for my Motorcycle I want to be in the 13's. Being a Car my guess is the low to mid 14's is good for Power and cooling Very low 15's should be close and High 15's to low 16's should be lean and hot running engine. Others may know better.

[GLASEM]

Did purchase one of those infrared pyrometers fro "Harbor Freight"
Temperature Gage seems to be reading OK. Shot the sensor on the right rear side of the engine and it was close to the Gage on the dash.

In my hast to get the car home......did not get a reading of the oil cooler or the thermostat in the wheel well. Very hard to shoot with a lowered car. Not much room in the fender wells.

Am al;so concern as to why the oil pressure drop when this happens.

Again....only occurs on the freeway. No issues last year at all......even when on the track

Don't think its a fuel issue. Exhaust temperatures were fine when shot at the exhaust outlet to the header. All appeared pretty equal.

[lindy 911]

As the oil heats it will thin resulting in lower oil pressure so the two are related. The cause of the additional heat is the unknown. There are really only two things that cause additional heat under normal operating conditions and that's fueling and ignition problems. If the fuel leans out it'll get hot and if the ignition timing is not right it'll get hot. When the motor gets hot the oil gets hot.

My 3.0 hot rod motor only goes to the front cooler when it's driven hard. Normal highway driving will not get it hot enough.

[Vincent Hill]

Originally Posted by lindy 911

As the oil heats it will thin resulting in lower oil pressure so the two are related. The cause of the additional heat is the unknown. There are really only two things that cause additional heat under normal operating conditions and that's fueling and ignition problems. If the fuel leans out it'll get hot and if the ignition timing is not right it'll get hot. When the motor gets hot the oil gets hot.

My 3.0 hot rod motor only goes to the front cooler when it's driven hard. Normal highway driving will not get it hot enough.

AGreed about the Oil pressure and temps. After installing an Oil Cooler I now have 1 bar at idle on a Hot day!

I have a question, WHen cold starting, does the car now have a Higher High Idle? Have you recently had to "LOWER" the Warmed up Hot Idle?

[GLASEM]

I have a question, WHen cold starting, does the car now have a Higher High Idle? Have you recently had to "LOWER" the Warmed up Hot Idle?

No to both questions

[GLASEM]

Bump.....

If it is the unit in the right rear fender well.......can it be cleaned? rebuilt? or replacement the only option?

[lindy 911]

Drive the car again and let it get hot. Stop and get out to feel the oil lines running under the car to the front cooler. Check to see if they are warm. If they are the thermostat is working. If they are not the thermostat is not working. Pretty simple. I have yet to see an SC that actually NEEDS the front cooler during normal driving, highway included.

[Bob Kontak]

I would first perform the thermostat test lindy speaks of to eliminate that variable. Highway driving will not impact it's function.

Highway driving has lower rpm and lower air flow. Are you absolutely sure the back corner where the air flows into the engine oil cooler is free of debris?

[lindy 911]

Another possible issue might be fuel delivery through the injectors. If the car sat all winter you could have varnish in the injectors and delivery system that could lean the mixture. You might want to try a good fuel injector cleaner in with a half a tank of gas. At any rate, I think a thorough and complete tune up is in order.

[GLASEM]

Already ran injector cleaner on the prior tank.

[Vincent Hill]

I am keeping track of these answers for if I have a problem because some of them are not ones I would think of like the Injectors leaning out the mixture. I also have another crazy question. Are you using or recently switched to "Shell" Gasoline??

[GLASEM]

Been running Shell gasoline since day one.

Personally from my research......looking at the oil system.....my gut feeling as an engineer is the rear wheel well thermo is the issue.

[lindy 911]

I offer this once again; an SC will run fine at proper temp without the front cooler. I have a 10.5:1 compression motor with big cams and it won't go to the front cooler at 70+mph unless driven hard. Normal freeway driving will only net a mid-gauge reading. A check of the oil lines running forward will tell the story in short order. Are you planning such a check?

[GLASEM]

The weather in Michigan since Saturday has not been ideal to drive it again.
Am planning to drive it this weekend for another trial and will use my infared laser pyrometer to check temperatures all over the car.

No one so far has mentioned that the internal engine thermostat could be an issue.