My oil pressure reading 85-911 normal or off balance?

[69porsche]

I have a stock 85-911 Coupe-I notice that my oil pressure is 95% at the number 5 mark with a slight deviation that It will go down to 3 mark and then jump back to the 5 mark and stay there....My oil lights and my oil temp are all in the normal range (normal being defined as no warning lights coming on, etc)...It starts off at 5 and after driving several miles 20 plus and 40 minutes drive time...it remains the same

Is there cause for concern? if so, any reason why it stays at that range...Thanks I used the search function but it did not provide any real help.

Thanks

[Superman]

Interesting. Are you saying your oil pressure gauge reads 5 Bar all the time, cold or hot?

[spuggy]

Pretty sure I had a pressure sender fail like that - reading unreasonably high.

It wouldn't be a bad idea to verify oil pressure with a mechanical gauge, even though it's probably far more likely the sender went wonky than that there's an obstruction in the return system, or the engine thermostat has failed shut etc.

You can test the gauge; pretty sure it's just a mini voltmeter with the sender providing a variable resistance. In which case, it should peg full scale if you disconnect it completely, and drop to zero if you ground it on the engine case. Or maybe the other way round, I forget...

[sky1jord]

From my '88 Owner's Manual, it should apply to your car.



That said, my understanding is that a healthy engine will register 1 bar per 1,000 RPM with the oil at operating temperature.

[69porsche]

Originally Posted by Superman

Interesting. Are you saying your oil pressure gauge reads 5 Bar all the time, cold or hot?

basically yes----I don't drive all the time but when I do---yes as far as I can remember

[69porsche]

Originally Posted by sky1jord

From my '88 Owner's Manual, it should apply to your car.



That said, my understanding is that a healthy engine will register 1 bar per 1,000 RPM with the oil at operating temperature.

Thanks I have my manual as well and was reading it but did not see anything about reading high.

[69porsche]

Originally Posted by spuggy

Pretty sure I had a pressure sender fail like that - reading unreasonably high.

It wouldn't be a bad idea to verify oil pressure with a mechanical gauge, even though it's probably far more likely the sender went wonky than that there's an obstruction in the return system, or the engine thermostat has failed shut etc.

You can test the gauge; pretty sure it's just a mini voltmeter with the sender providing a variable resistance. In which case, it should peg full scale if you disconnect it completely, and drop to zero if you ground it on the engine case. Or maybe the other way round, I forget...

Thanks-Gives me a good starting point!

[69porsche]

Is this a relatively easy fix? if the diagnosis is correct?

[manbridge 74]

Best practice would be to put a standard oil pressure gauge in the pressure side of lubrication circuit to confirm what the dash gauge is reading.

[patkeefe]

Originally Posted by manbridge 74

Best practice would be to put a standard oil pressure gauge in the pressure side of lubrication circuit to confirm what the dash gauge is reading.

[spuggy]

Originally Posted by 69porsche

Is this a relatively easy fix? if the diagnosis is correct?

Although it has worked for some (most of who say they wouldn't dare do it that way again), it's considered dangerous to attempt to remove the sender from the block it screws into while fitted to the car. Sender should be on the block pretty darn tight, and it can easily over stress the hollow through bolt. If the hollow bolt breaks off in the case, you may have to drop the motor to address it.

So remove anything in the way (A/C bracket if fitted etc), remove the oil line & through bolt. Sender and block then comes out as an assembly; remove the sender from the block in a bench vise. Assembly is the reverse of disassembly etc.

Gauge or sender?
mechanical oil pressure gage
Another Oil Pressure Sender Replacement Thread with pics
Question on replacing the oil pressure sender
Are all VDO 0-10 bar oil pressure senders the same?
Oil Pressure Sensor loose?

[69porsche]

Looks like I will make an appointment with my mechanic and see what he says. Hopefully it does not cost me a kidney.

[manbridge 74]

5 bar reading at idle too? What about ignition on only? Perhaps just a dirty connection at the sender. I wouldn’t sweat it too much...

[69porsche]

Originally Posted by manbridge 74

5 bar reading at idle too? What about ignition on only? Perhaps just a dirty connection at the sender. I wouldn’t sweat it too much...

5 bar at idle and 2 bar on ignition only.

[Flat Six]

Typically you'd expect to see (warm oil & engine) 1 bar per 1K rpm.

[al lkosmal]

It sounds to me like you have an intermittent connection to the pressure sensor. If you disconnect the wire that connects to the pressure sensor, the gauge pegs at 5......if the wire is partially broken/frayed or the connection is somehow intermittent it can peg at 5....hit a bump. make temporary contact...jump down to 3 ....hit another bump....disconnect...peg at 5......you see where I'm going with this?

[manbridge 74]

Agree on dirty connection possibility, should be zero with ignition on but engine not running.

[69porsche]

Does anyone have photos of where the said oil pressure sensor in question located? and a photo of the pressure sensor as a part itself?....I do not have a lift or any type of garage that I can work on the car-but perhaps, I might be able to do a very simple things so I can isolate and talk intelligently about the issue when I take it to the shop.

[pampadori]

Just to the right of the alternator fan. Its that large cylinder looking thing with a wire on the top of it.

[69porsche]

Thanks to all for the info----Stupid question, but if I was to replace oil pressure sensor myself, does the car need to be drained of oil, etc.....is it plug and play or am I oversimplifying it?