kmm944

I know this is an old can of worms reopening, but after examining almost all posts of the kind, over and over, I could not find a feel good resolution... I ran the car hard for few traffic lights, after I came to a low speed creep to look for parking on the street I noticed the " ! " and low oil pressure lights came on, and the oil pressure dropped to 2 bar at 3k and when stopped, dropped to 1 bar! No metallic noises or weird vibrations engine was smooth. I parked and left it to cool off, the next morning I started it and no ticking no ratleing noises, all sounds and vibrations were good, but oil pressure was low at 2 bar and all the above mentioned lights were on, after warm up pressure down to 1 bar, after couple of light revs pressure flickered to 5 bar and then back to 1 but then flickered more and drops to "0", and brake lining and brake system lights come on! Now engine is smooth and normal sounding except all the above. WTF? I have less than a bar of pressure at the instrument cluster gauge, no metal noises, I checked cluster is good, wiring at sensor is good cranck bolt is in the proces of being checked but the pulleys are straight on and when removed the filter it's full of oil so its priming ok and pump gear must be straight on! I noticed when engine is running I pull the dipstick and oil actually becomes higher than the top mark??? Other wise oil is at just above top notch. And again engine is running smooth and quite with instant trotle response. Any input will be apreciated...

dizzyj

failing oil pump?

kmm944

Soooooo..., Is it repeatable, do I clean and reseal it or its a one time item?!?

kmm944

... tired, I meant reparable ...

krystar

it's either a small problem or a big problem

small problem: your oil pressure sender or sender signal wiring or sender ground wiring broke.

big problem: rod bearings or oil pickup tube cracked.

i'd start with diagnosing the sender electricals.

kmm944

I am strongly hoping for the electrical, I will have to remove that "PITA" sensor and install a mechanical gauge to verify the pressure..S#@T

kmm944

What are the voltage or resistance values for the oil pressure sender itself?

dizzyj

while I would agree to hope for electrical, my gut feel is that it would be a work/doesnt work situation, vs a low oil pressure.

you could do some easy thing, change the oil/filter, check for any blockage. Otherwise, your looking at some decent engine work to get at the oil pump/pickup tube.

kmm944

Filter has couple hundred miles on it, and its original porsche.., now I don't question the idea but is it, if the valve in the filter is stuck open no oil pressure and if stuck closed, it is high oil pressure???

fortysixandtwo

It would be good to verify the low oil pressure condition with a mechanical gauge. Installing one will require you to get an adapter that goes between the oil thermostat housing and oil filter.

I doubt the problem is in the wiring. A break in the circuit, will cause the gauge to peg at 5+ bar. The warning light and gauge are driven by separate wires (sending unit controls gauge reading and warning light separately). So, if both the gauge is reading low and the warning light is on, the sending unit is relaying a low oil pressure condition. This can be due to the oil pressure actually being low, or the sending unit's pressure sensor has failed.

fortysixandtwo

The filter is down stream of the oil pressure regulator (OPR) and up stream of the oil pressure sensor (OPS). If the filter was clogged and the bypass valve (most filters have a bypass valve so they limit the filter's pressure loss when it becomes clogged) is stuck closed, you would see low oil pressure. This is because the oil pump would be dead heading against the oil filter and the OPR would be redirecting the oil back into the pan.

If the OPR is stuck open you would have low oil pressure, because a large volume of the oil will be directed back into the pan, without going through the bearings.

The filter valve being suck open will not hurt oil pressure. But it will cause the oil to not be properly filtered.

If the OPR was stuck closed, you would see very high oil pressure. This, sometimes, will cause the oil filter housing to rupture.

dizzyj

I would definitely confirm if you have low oil pressure with a mechanical gauge before driving the car again. These cars do not respond well to low oil. my gauge was pegged and I spent a day debugging the wiring just because I wanted to be sure my pressure was ok.

V2Rocket

could be grounds, if the other lights are coming on. mine reads 3-3.5 bar at idle and 5bar at around 2000rpm and up, but sometimes with the headlights and foglights on even driving around (~3000rpm) it will only read 3 bar. grounds need to be checked...

kmm944

WOW "fortysixandtwo"... This is great input, thanks!!! I m heading for the store to get the gauge, it should be a spin-on adapter right?
So it is a possibility of bad filter, OPRV, OP-Sending Unit... if its light situation !?

kmm944

Still I wander what readings I should get when I connect the DVOM to the pressure sending unit?
Any ways thanks to all you guys!!!