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Re: 535 oil pressure (archive)
[ Follow Ups ] [ 5-series (E28) Message Board ] [ Msg. Board FAQ ]
Posted by Bob on October 23, 2000 at 02:28:09:

In Reply to: 535 oil pressure posted by Peter on October 22, 2000 at 20:37:30:


I have an 88 535i that runs great with 140k miles on it. But on starting the car in the morning the oil pressure light stays on about 10 seconds+, much longer than I'd like. I replaced the sender switch and it was the same. I hooked up a VDO guage temporarily and got 70 lbs. at 5000 rpm (warm engine) and about 12 lbs at warm (not hot) idle, which seems good and within spec. I read somewhere that the oil pump pressure relief valve doesn't always seat. The sender itself is high in the engine so it receives pressure last. I checked those oil spray bar bolts when I adjusted the valves and they were snug. Does this happen often with the big six?
I won't hesitate to replace the oil pump if that helps but are there any other possibile causes?


------------------------------------------------
From my experience it is more common than not.

The anti-drain back valve washer in the oil canister mounting gets hard and doesn't seat well eventually, though I cannot say for certain that this is the problem. BMW says that the valves should not be removed from the mounting, and that the entire assembly must be replaced when the washers get hard from engine heat. For this reason, BMW won't sell the 30 cent washers, and a new part is $250+. You can try installing a new washer from Lowes hardware. Bring your old one with you to match it up. It takes a while for the oil siphoned from the filter when the car sits to be replaced and build pressure.

BTW, older M30 engines didn't have the anti-drainback valves installed even though the BMW part # moulded into the casting is the same, though the casting is quite different INSIDE!

Yes, the oil pres relief valve can get stuck partially open from varnish. The pump is fairly easy to remove and clean in solvent. Worth a try. before you replace the pump, fill it with Vasoline or STP so it will prime quickly.

12psi at idle is not wonderful, but as long as it comes up quickly to 25-35psi at 1000-1200 rpm and shows 50psi by 2500 rpm you are fine there.

bob

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