I have a 1973 911T with the 2.4L MFI. I took the car out today for a short run and with in 5 to 7 miles, my oil temperature gauge indicated nearly 260 degrees. Out side temp was about 81F. I got home quickly and as I pulled into the garage, I noticed that the gauge now indicated 210 to 220F. I have had this problem for a while now, but since I work out of town, and rarely get to drive the car, I haven't really done anything yet to fix this. The oil thermostat was changed out 4 months ago thinking this was the problem. It did not help. I am running Mobil 1 20W50. The engine was rebuilt less than 1100 miles ago.

Thanks,
Scott

 

I know little about the 1973's, however, start with the basics. Is the intake fan turning? Belts are to appropriate tension. Oil level is correct? When the engine is at operating temp, or hot as you described is the front cooler also hot to the touch? If not then the line is not patent. Mechanically or physically blocked.
regards,
Steve

 

A little additional background on my car.
There is no front oil cooler, only the engine mounted cooler. Fan is turning, belt is tight and not slipping. Timing is set correctly, mainly due to the assistance I have received on this forum. Oil level is at proper level on dipstick when engine is at temp, which takes about 5 minutes of speed limit driving at 45mph. Yesterday, I apparently developed a small leaker on the drivers side. Location unknown. I am planning to pull and replace the 30 year old engine mounted cooler when I finally get some time off from work.
Scott

 

Even without a front oil cooler, your temperature should not be anything like this high (and even if you added a front oil cooler to help, you still would not be addressing the main overheating issue). Also, I doubt if small oil leaks, which are common to all 911's would have anything to do with the problem either... unless, you are dealing with something like a damaged oil return tube, which could also be a leak source too.

Check the oil screen at the bottom of the oil tank, if it is clogged, the oil will not circulate properly, and the engine will overheat.

I'm no mechanic, so I'm only repeating here what I've heard and read (since I've had no overheating problems with my 2.7 911S... it also does not have a front oil cooler).


-MAS

 

Before you take anything apart, you say you seldom drive the car. Is something perhaps nesting in the engine? I would have a really good look in there before I do anything else. The new leak could be related to the really hot oil fining a new path. I agree these temps are way out of line for your car at that ambient.

 

Of course, we are assuming that the oil temp gauge is reading accurately.
Perhaps, start there before you go off on a snipe hunt.
regards,
Steve

 

I wondered about the gauge too. Just before I pulled into the garage the gauge was still reading 260ish. As soon as I stopped the car and shifted to neutral, I noticed the gauge now read about 220. How can I verify the gauge is functioning properly, and on that same track, the sender?

 

Could also be a bad sender unit. There was an article sometime ago, and I can't remember where, about testing the oil temp sender and gauge for callibration using those two units, pulled from the car, boiling water (212 F) and a 12 volt battery.

As a caveat, a number of years ago, I purchased a new VDO, numbererd temp gauge and sender from a now (apparently) defunct company called Imparts. I was amazed at the decrease in my 84 Carrera's operating temp. Only last year, did I fully realize that the thing was malfunctioning new, out of the box!
regards,
Steve

 

Check your grounds. A bad or missing ground to the chassis from the engine can cause sporadic gauge readings as well as other issues.

 

I vote for a bad ground, or bad/incorrect sender. I have never seen the temps go down as fast as you describe.

I am assuming with your recent rebuild, your cooler is clean.

Are you sure you are not running too much advance? Plugs and points correct? Brakes dragging?

Just another thought: are you running too lean?

Good luck and let us know.
Even if you get it sorted, a front cooler might still be a good idea.

Paul