911 Overheating - Drop In Oil Pressure - Help!

[guidob222]

I have a 1982 911 SC with 66,000 original miles. It has had new ARP head studs, pop off valve, carrera chain tensioners. I have never had an overheating problem until now. I recently changed my oil @ the 3,000 mile interval - and cleaned out the engine oil sump screen like I always do. I added 10 liters of Mobile Clean 5000 10W-30 Motor Oil - then 1 more liter of oil to get the oil in the middle of the dip stick. TOTAL OIL - 11 LITERS. OUTSIDE TEMPERATURE AROUND 85 DEGREES / AC has been removed - The car drives fine for about 30 minutes of regular street driving - if I reach above 60MPH, I notice a loss of oil pressure and the temperature starts to rise. I just tested the car with the same scenario & the car reached a little over 266 degrees/130 celcius after going over 60 MPH after a leisurely drive around the neighborhood. I shut the engine off to cool for thirty minutes, then drove home. I touched the trombone oil cooler and it is hot after street driving - so that should mean the oil cooler and thermostat are working, right? Could I have installed oil sump screen/plate/drain nut incorrectly to block oil flow? Is there a specific position/orientation that the sump screen/oil drain plug needs to be? I know not to install the drain plug under the oil pick up tube..I am pretty sure I did not do this. I have all original oil lines. Should I drain the oil and check the oil sump screen orientation/plug? Should I try a thicker oil 10W-40? If I do another oil change - can I use the new filter I just installed? It has less than 100 miles on it. Do I need new drain plug gaskets as well? Please let me know your recommendations. Thanks!

[Walter_Middie]

Was this your first drive after the engine work was done? Or was it OK until the oil change? Or maybe you didn't drive it very hard until the oil change?

The things that come to mind first are:
Cylinder air deflectors installed incorrectly.
Too much timing advance.
Running Too lean.
Temp gauge not working correctly.

And yes, check your oil screen again. You can re-use the oil filter.

Who did the engine work? Have you found any silicone gasket maker material in the oil or on the screen? Could something be blocking your oil passages or oil squirters?

[tonythetarga]

10W30 is TOO light. You want 20-50, especially for the midwest heat of summer. If you drive at all during winter you could switch to 15 -40. Your filter should be fine.

[911nut]

Also, keep in mind that engine speed and oil temperature are directly proportional. You will always see the highest oil temps as a result of prolonged highway driving.

[Gogar]

I think if you do a search, you can find a picture of the correct sump plate orientation, so you don't have to go through all of that draining, refilling, etc.

But yes that's too hot. Did you have 10-30 in there before, or something else?

edit; Tony beat me to it!

[Gunter]

Drain plug orientation below.
I use 15W40 because of the Diesel-additives (High temp and pressure) 10W30 sounds low for Summer driving.
I replaced the Trombone with a Carrera cooler.
Don't use a bra because it blocks flow.
Re-use the filter, check the sump orientation, check for fan belt slipping.
You don't mention if the pressure was good on the gauge.
Where was the needle on the temp gauge? Still in the white?

needle on the temp gauge?

[guidob222]

Thanks so much for all of your responses. No - I had the work mentioned done over a year ago...that car has run great since the work done. Yes - I have defintely driven it very hard since the work. I always run 10W-30 with no problems. I have had no overheating before - just since I recently changed my oil. I never find anything in my sump screen - just oil. My drain plugs are both magnetic and all there is is slight dirty very fine metral residue that I wipe off with a paper towel every oil change. I took my wife on a trip to Evansville, IN for our Anniversary - put about 600 miles on the car - it drove beautifully. I opened it up - outside temp was in the 90's...my car NEVER gets above the mid point of the oil temp gauge (250 degrees). The car never got into the red gauge - I wouldn't let it...pulled over and shut her down to cool off....I shut her down at 266 degrees/130 celcius. My sump screen cover with drain plug is pointing to the front of the car - not to the left as pictured....does that matter? Also - is there a WRONG way to install the sump screen? I am going to drop the oil here later this evening to investigate...this is driving me nuts. Thanks for all of your help...you all have been a blessing. Any more suggestions/help - just let me know. Thank you!

[tonythetarga]

I guess you can run whatever oil you want...it's your engine! But the factory never recommended an oil that light even for winter time use. The Shell Rotella 15-40 as Gunter mentioned or a 20-50 is what you want.

[Steve@Rennsport]

Hi:

If I might offer,..


1) 10w-30 is too light for air-cooled cars except when the outside temps are close to freezing. Use a good 15w-40, 15w-50 or 20w-50.

2) Sump plate and pickup screen orientation are both CRITICAL. Failure to install those correctly results in cavitation and thus increased oil temps (which results in low oil pressure).

3) Mid point on the oil temp guage is around 250 deg F and thats too damned hot. Engine life suffers, oil leaks become an issue, and performance REALLY suffers. I would recommend that you do something about that (Carrera cooler).

4) Make sure you use a Mahle oil filter. Don't use an American one!

[guidob222]

Thanks guys - I will take back my oil and try to find some 20W-50 conventional oil. I try to stick to Mobile; however, I don't know if I will be able to find that where I live. Do you recommend any special brands of 20W-50 oil if I cannot find Mobile conventional? Thank you so much for the exlanation of how critical the orientation is - I will drop my oil tonight and re-do. Please let me know brand recommendations on oil...I only have autozone in my area. Thanks!

[guidob222]

Thank you - just called autozone - they have valvoline conventional 20W-50...going back to take 10W-30 back and get the 20W-50....is valvoline okay?

[guidob222]

Also - is there a wrong way to install the sump screen? Can you explain exactly how to re-install? Thanks!

[Eagledriver]

The sump screen should only have a hole in one spot for the pickup tube so you can't install it wrong. The orientation of the sump plate can be wrong so you need to look at the pickup tube and make sure the sump plug is oriented to prevent hitting the pickup tube. Gunter is probably correct in his picture but I can't confirm as I'm not home.

If you installed it wrong you may have damaged the pickup tube. It is epoxied into the pump and if the epoxy cracks or breaks it will suck air at the pump instead of oil at the pick up point. You can wiggle the pickup tube with your fingers. It should be tight and not move. You may also be able to see where it enters the oil pump with a flashlight.


I think Valvoline 20-50 is OK but there is lots of information in these forums about motor oil and lack of additives. Gastrol GTX 20-50 seems to be the only conventional oil with the additives we need.

-Andy

[djpateman]

Brad Penn oil is the best conventional oil by far; it is the old Kendall oil and has all the required additives. Royal purple oil is the next best. Most of the rest do not have the proper additives for our air-cooled engines.

http://forums.aircooledtechnology.com/forumdisplay.php?f=47

[Wil Ferch]

Even some senior people have gotten some things wrong on this post.

In the 70's Porsche did not "trust" multi-grade oils and insisted you use straight 30 weight in the summer. Why would today's 10W-30, driven in summer conditions, be much different? I don't run this light myself but I don't think it would hurt the engine. Anyone?

Also..."midpoint" on the gauge, depending upon the model year is either around 210 or 230 degF. Midpoint ( 9o'clock) would never have been 250, IIRC. Ask NoHo to confirm...

- Wil

[ramonesfreak]

ive been using 5W-50 castrol synth. it was my first oil change since owning and i probably wont use it again, but my car has run with great pressure and low temps even in over 90 degree summer heat.

[Gogar]

On a stock SC oil temp gauge, the line at the 10-oclock (2/3, whatever it is) mark is 120C, 248F.

[frogger]

The comment about loosing pressure above 60 mph concerns me. Is that because you're shifting into a higher gear and dropping rpms, or does that happen in a constant gear but increasing speed (RPMs), or at a constant speed? The pressure should not drop with increasing RPMs, maybe drop just a little bit at a constant speed as the oil temps increase. How much does the pressure drop?

[Wil Ferch]

Cogar, you are correct, the mid-80's carrera gauge reads the same.

The 10 0'clock white line is 248 degF.

With the 8 o'clock line at 194 degF..that would make midpoint about 210 or 220, since the gauge is not absolutely linear and symmetrical from horizontal. Earlier gauges place the midpoint closer to 230 as I recall. A quick call to North Hollywood Speedometer would confirm the various configurations.

- Wil

[weare138]

Originally Posted by Eagledriver

If you installed it wrong you may have damaged the pickup tube. It is epoxied into the pump and if the epoxy cracks or breaks it will suck air at the pump instead of oil at the pick up point. You can wiggle the pickup tube with your fingers. It should be tight and not move. You may also be able to see where it enters the oil pump with a flashlight.



-Andy

Beware the damged pickup tube... My 78sc had identical symptoms to yours. I ended up tearing apart the engine (it had plenty of other problems to) and I discovered the oil pickup tube was loose and there was a little notch in the tube from something contacting it like a drain plug.