735i '88 Oil Pressure Sensor

I have a 1988 735i with 125,000 miles and the oil pressure sensor message came on a few weeks ago after the first below freezing night. The mechanic changed the sensor and checked the car out and everything
seemed OK. The other day, also below freezing, the message came back on. Since then it has been mild and no message. Any ideas out there? I have been driving the car the past few days, it has been in the 40s and everything seems fine. Should I be concerned?
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scott wrote:

I wouldn't worry about it. As long as you have oil.
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Bob wrote:

That's some really BAD ADVICE.. if the oil pressure is low - the engine will be ruined.
A rather common fault with the E30 engine used on that car - the oil spray bar for the camshafts is held down by hollow bolts that also pass the oil under pressure to the spray bar. The bolts can loosen up causing this sort of symptom. Since the oil is no longer getting to the spray nozzles on the bar - the camshafts aren't lubricated correctly and will wear rather quickly.
Cure is new bolts - BMW added some locking compound to the new bolts. You can tell if you have new bolts by opening the oil fill cap and looking for the most forward bolts. If you have new ones - the heads will have a groove cut in the top. If no groove - it's the old bolts.
Other possibility is a failing oil pump, or the wrong oil viscosity for cold weather, or a failing oil pressure sender. Since your mechanic replaced the sender - it leaves the other possibilities to check. I'd want a real oil-pressure test done on the engine (where an oil pressure gage is screwed in place of the oil-pressure sensor.
I would NOT simply ignore it. Bad advice.
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True. But BMWs seem to be fitted with the most unreliable oil pressure warning switch I've known. All mine have had this fail, and some more than once. So before checking anything else I'd try a new one, or do a proper pressure check.
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Dave Plowman (News) wrote: >> That's some really BAD ADVICE.. if the oil pressure is low - the engine

Dave - if you reread the original posting - his mechanic already replaced the oil pressure sensor.
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Indeed. And it's quite possible the new one has failed too.
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Dave Plowman (News) wrote:

And at this point the best test for this would be to screw a real gage into the head and measure the oil pressure.
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wrote:

Same thing happened to me, same car. I had it checked at the shop. Oil system is okay, dashboard is known for horrible errors and maintenance. It also tells me "brake light" when the light is fine. Stereo also beeps "CLN" for "clean" for the tape heads when there is no tape playing. They want one grand to replace dashboard, I said no way. 1988 is horrible for electronics, I've fixed about everything electric on that car, seats, windows, you name it.
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Absolutely. Certainly before dismantling the engine looking for faults that may not exist.
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admin wrote:

The best, but not necessarily the most cost-effective. These senders are unreliable for a reason: they're cheap (or is it the other way around?). About $6 new. I'd probably spring for as many as 3 of 'em (I seriously doubt the failure rate is over 66% new; and I've got two running M30s at my place now, so the odds are good I'll need 'em someday.) and replace them before paying for a pressure check. Total cost would be about $20 for the senders. If all indicate low pressure, then I'd believe them (collectively) and start troubleshooting the oil system - starting with the banjo bolts. -- C.R. Krieger (Been there; done that)
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If you DIY, probably as cheap to buy a gauge and check it yourself - it doesn't need to be a super accurate gauge as a few psi either side doesn't matter.
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If the light comes on soon after starting the car, my guess is that the oil is too thick as a result of the cold weather. If this is true, you should try using a lighter weight oil for winter, perhaps a 5w30 or something like that.

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