Porsche Repair: 1980 911 SC Green OEL Light, oil pressure gauge, low oil pressure

Question
I Have a 1980 911 SC after letting the car warm up 15 min or so the Green OEL light and the Brake
light come on at idle once i give it a little gas to about 1000 rpm the lights go out, until it idles back down to about 600 rpms. Oil pressure and temp seem to be normal. Oil level on the stick is 3/4 of the way to max. I'm using Castrol 20-50 motor oil. Any suggestions ?

Answer
Followup.........

Hi again...

I hit the send button before I answered you second question.  About the brake light.  I'm concerned the brake light is wired incorrectly.  If it is supposed to show brake pad wear but comes on only at idle...this is suggestive of a mixed wire situation.   If you can trace the wiring to get at the brake light wires and the oil light wires at the same time, this can be tested.  Let me know if you can do this.

Dave............


Hi Kevin,

The green oil light is designed to supplement the oil pressure gauge.  In the case where you are merrily crusing on the freeway ay 65 mph and not paying particular attention to the oil gauge, the light will alert you to a VERY low oil pressure more readily than the likelihood you will notice the gauge.

I suspect what is happeing with your car now is its age is beginning to show.  It is typical of every engine to have it's lowest oil pressure reading at idle...and should not be of great concern IF the pressure rises dramatically and proportionally with the gas pedal movement.  Higher revs, higher pressure.  Higher engine load, definitely higher pressure.  If these movements aren't your "norm", there's something else going on.

So...if your engine has some "maturity" to it and is not freshly rebuilt, let's say, then all is well.  I would definitely begin to think of your oil pressure gauge as an indicator of "normal".  Look at it as if you could see inside the engine every moment.  Your engine is "normal" when the gauge is fairly low at idle, but it acts "normally" as it ramps up in relation to acceleration, right?

Your job, from now on, is to watch for and react to abnormalities.  Crusing on the freeway and the pressure falls to zero.  Ideally you'll have the engine shut down before you even see the green light, OK?

Dave