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rizzo

Oil Pressure Too Low

12 posts in this topic

Hello all,

My 04S with 101K threw up a rather alarming warning last week.

Scenario: I was making a right turn onto a neighborhood street (under 20mph) about ten minutes after starting the car and the alarm tone sounded with the dashboard showing "Oil Pressure Too Low"

I immediately pull over and shut down the engine.

Check oil level and it's spot on.

Restart car and drive it slowly home. Never got warning again.

As a precaution I changed the oil filter. When doing so, I sampled some of the oil coming out. Nothing unusual about color, feel, or odor (no noticeable metallic particles to my fingertips).

The battery has been in the car since I bought it in August of 2008 so it's well over two years and likely more than three years old. I charged the battery for 24 hours and have driven it another 300 miles or so with no return of that warning.

The oil temp has remained the same (just under 200 degrees) for all miles driven since the warning appeared.

Could this warning be among the usual suspects of a low battery, failing sensor, or an engine about to grenade?

I have used Durametric to check for codes and warnings. Nothing is stored.

Thoughts?

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The temptation in these sort of cases is to first shoot the messenger. IE - blame the sensor (or battery, etc.)

The factory workshop manual gives a procedure to test the oil pressure. If it was my vehicle, I'd be doing that before driving the car anywhere. The cost of grenading the engine would certainly hugely outweight the costs involved in getting the vehicle flatbedded to a dealer to have the test done. At best - yes - you can certainly hope the messenger deserves shooting, at worst is ignoring it and hoping it doesn't happen again only to find that you've destroyed the engine by so doing.

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I've tested the oil pressure per the instructions in the service manual.

I have 2.2 BAR at idle (high according to the manual)

I have slightly over 4 BAR at 4,000 RPM. (still high according to the manual)

The oil pressure dashboard warning light did not come on until after the engine was above 1500 RPM. It seems the computer is recognizing that it's not getting the info it needs at a given rpm.

But upon start up/ warm up there was no warning at all. No warning until above 1500 RPM.

Any technicians out there have any thoughts?

The manual states:

• The oil pressure may be too low for a number of reasons:

• Oil is diluted

• Oil pump is faulty

• Bearing clearance is too large (e.g. crankshaft bearing)

• Oil level is too low

• Oil pressure regulating valve is faulty

• Incorrect oil has been used - use only oil that has been approved by Porsche for the measurement

If anything my pressure is on the high side for this test. Oil came to temp in the driveway after 8-12 minutes of idling. Maybe after 15-20 minute drive the pressure would come down a little further to match the numbers of the manual?

If you guys were in the shop, what would you do next?

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I know this might sound hokey, but I would change the oil filter first to see if it helps. I dont know if this engine is one of them but some engines and filters have a bypass if oil pressure gets too high. In any event its an easy and inexpensive thing to try. Your results so far look encouraging. After that I would definitely be looking at the sensor

PKN

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Are you using recommended or quality motor oil? As you ahve already tested the pressure with a manual gauge and it is above spec, I would then replace the sender unit as it might be failing causing a false warning to occur.

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Thanks guys!

PKN - I changed the filter prior to this test. Thanks!

wvicary - I am using Mobil 1 0W40 and there is about 5K miles on this oil. Change the sending unit?

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I agree with you, change the sending unit. I think they are around $40 at the dealer.

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If you verified that it has good pressure and warning light is still on, prolly a sending unit. If you have a multimeter you can check the signal from the oil pressure sender to DME to make sure it has a good signal or not. But prolly just easier to throw in a sending unit and if that dont fix it then you can really dig into it. If it dosent let me know and I will tell you exactly how to check circit and send u diagram if need be.

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Test the pressure with a manual gauge. Has the correct motor oil been used as sludging can cause problems over time from the incorrect oil being used.

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It depends on why it's low, could be from a sticking pressure valve due to sludging. They sell a pressure tester that also has a port so you may install the factory oil pressure switch and monitor it's operation whilst on a road test. If your oil pressure is low you need to address the problem straight away or severe engine damage will result.

I'll ask again, do you know the service history of the vehicle and what oil has been used?

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Take a look at Porsche service campaign #W738 for reprogramming of the DME. What I read from it is that the manufacturing tolerances for the oil pressure spray jets in the block used for piston cooling were broad enough that the instrument cluster could sense a low pressure condition very intermittently. Since this is a continuous monitor it could set a fault anytime oil pressure drops out of specs pre-programmed into the instrument cluster. This is not necessarily going to last long enough to cause a dangerous situation. The fix, according to the bulletin is a reflash of the DME via PIWIS.

What they will tell you at the dealer or your service guy that this doesn't apply to your car. What they DON'T tell you and they probably don't recognize, is that if the car has EVER been reflashed it could have the same software as cars covered by the bulletin.

I don't have a copy of this bulletin that I can fax or e-mail to you but it may be available elsewhere on this site.

HTH,

Craig

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