Oil Pressure

[agee11]

Lets start when I start the car 1999 996 Cab. The oil pressure shows just above 4.0 once car is in normal temp to drive 180. Outside temp 75 or so. Oil pressure is about 3.0 when ouside temp over 85 oil pressure drops to 2 or so. When at idle pressure drop under 1.0 Need to know what I can do before it ruins my engine. car has about 140k let me know if anyone has this problem and can help. Thanks

[ivangene]

IMO this is completly normal and well withing the limits of acceptable. - as long as it doesnt go below 1/2 at idle I would not worry - your car moves a ton of oil around..almost more than any other car out there... it is not an issue to see these numbers...

[Richard Hamilton]

Apart from idle, you don't mention revs, which would give a much better indication if there is a problem. What pressures do you get with the water temp at 180, outside temp 80 or so, at 3000rpm and 5000rpm?

[whall]

This is the note from the MY03 Carrera Owner's Manual (page 80):

"With a warmed-up engine and at a speed of

5000 rpm, the engine oil pressure should be

approx. 3.5 bar."

I would imagine the above note would apply to your engine (MY99/3.4 litre vs. MY03/3.6 litre) as well.

Bill

Edited August 27, 2009 by whall

[1999Porsche911]

Should not fall below 1.5 bar at idle and should be over 4 bar at engine speeds above 3000.

[agee11]

AT 3000rpm its about 2.5 to 3 same for 5000

Apart from idle, you don't mention revs, which would give a much better indication if there is a problem. What pressures do you get with the water temp at 180, outside temp 80 or so, at 3000rpm and 5000rpm?

[Loren]

A car 10 year old car with 140,000 miles will not have like new oil pressure - everything is somewhat worn.

If you are using 0W-40 or 0W-50 oil I think your oil pressures are about right for a 140k engine.

Depending on how you drive and handle maintenance you could get another 100k out of this car (or more).

All IMHO of course.

[Richard Hamilton]

I have only seen two M96.01 engines stripped down, and what surprised me (although the rebuilder said it was common) was that the bearing journals and shells, pistons and rings, were in remarkably good shape. I haven't searched here, but I don't recall many incidences of low oil pressure. Personally, I think 2.5-3.0 bar at 5000rpm is low. That's only 37-45psi.

So if it is unacceptably low there can be 3 causes. Leaks, wear, or that the oil pump isn't producing pressure. If it was me, I would look into changing the oil pump pressure relief valve piston and spring, as the parts are cheap, and I think it can be done on the car. According to the manual, the engine has to be reemoved to change the oil pump, but someone else here may know if it is possible to do on the car, as that would be my next thought.

You don't say what oil you use, but if you can't get the pressure up any other way, you might consider changing to a heavier weight 10W-50 or 15W-50. You might want to do that anyway, with the mileage you have. I think that is what Loren may be intimating.

[stobbie]

my pressured dropped to 0.8 at idle with a hot engine, this was with 0W40 oil.

I got a little worried and have changed my oil to mobil1 5W50, now I have a pressure of 1,8 bar with a warm engine, about 1.3 with a VERY hot engine on a hot day. Much better. But now pressure is at the maximum of the scale, 5, when revs are > 2500 RPM..

Is that too high? Will it destroy oil seals?

[dcdrechsel]

Question for 1999 Porsche 911.How did you arrive at the conclusion that oil pressure must be 4 bar at 3,000 rpm when the manufacturer is saying 3.5 at 5,000 is ok ?

Dave

[SA321]

interesting conversation. I just replaced oil pressure sender on my 996c4s 2003 and strangely at frist it read 5 even at idle. (no i didnt accidentally swapped wires) only after i took car for a test drive and revved it up to (almost) redline pressure started showing 3-5 depending on revs and around 2 at idle. is this normal?

[RFM]

@ SA321, assuming that the test is performed starting with a cold engine and the recommended oil weight, which become warmer while driving, everything seems to be OK.

[vitamincpp]

Well, I was a little worried too, because I own the car for 2 weeks now, and my pressure when engine is hot (above 95C) drops to 0.5 and even below. But what I've noticed is that when I start it cold the arrow goes little below 4 and stays there even if I rev the engine to 3k rpm. It is like stuck at just below 4. That makes me conclude that the gauge is mis calibrated and the arrow shows the actual value -1. I have no warning lights and I have gone to diagnostics before buying the car and at Porsche service they haven't found any errors.

[whall]

There are two possible indication problems. The first concerns the oil pressure transmitter. It is the usual culprit and the least expensive to remedy. The other is the gauge in the instrument cluster. With the ignition switch on the "OFF" position, the oil pressure gauge needle shold be below the 0 point of the gauge....about a millimeter below. With the ignition switch in the "ON" position (with the engine static) the nedle should move to the 0 point. If this isn't the case - and the previous owner hadn't replaced the instrument cluster faces (incorrectly re-indexing the oil pressure needle) - you probably have a bad instrument cluster.

Because the oil pressure "idiot light" is the final arbitor when determining whether or not there is sufficient oil pressure - and it is not illuminated - you probably have oil pressure. To be on the safe side I'd suggest taking the car in and have a technician put a direct reading gauge on the engine. BTW, the Boxster/Cayman series has no oil pressure gauge, relying solely on the idiot light.

Bill

Edited September 22, 2010 by whall