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weber magic

Oil pressure light came on.

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Driving from my house to my sisters (about 10 miles all dual carriageway 60mph +) yesterday in my 518i m10 4 cylinder car and when I arrived at idle the oil pressure light began flickering. So I shat myself and switched it off.

No big puddle under the car although lower timing chain cover was very wet with fresh oil and the sump appeared to be leaking almost all the way round in equal parts. I let the oil drain back into the sump for 30mins and checked the level which read a quarter high on the dipstick measurement, so plenty of oil in it.

I have worked out that it has the wrong oil pressure switch fitted but judging g by the fact I've been driving it for two weeks and it's been ok I doubt this is the problem although I have the correct one on order.

Now, it is leaking from the lower timing chain cover and the sump as described above but it's not dripping or coming out at any great rate. Could these leaks be enough to create low pressure, they don't seem bad enough to me.

I have since topped up the oil and the same thing occurred only it happened more quickly this time. The engine runs fine and has no knocks or rattles. Obviously I have stopped driving it until I work out what the problem is. Leaks will be cured anyway but I am not convinced they are bad enough to create such low pressure.

Any opinions would be great fully received, thanks.

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Wow, that sounds like crankcase pressure problem, I'm not familiar with these 4 pot engines but do they have any sort of crankcase breather system? If they do this could be blocked.

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It does, very similar to an M30, straight off the cam cover and recirculates to the induction boot. I will check it out.

Car is also hideously bad on fuel. Recon I'm only gonna manage 200-225 on a whole tank, it runs and idles well but feels like it's being choked when driven. Could bad crank case ventilation also cause this?

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In general a drop in oil level doesn't (in my experience) lead to a low oil pressure light unless the oil level drops below the oil pump pickup in the sump. At that point things can get very bad very quickly as the pump can't do it's job.

As long as the engine has the correct oil (and pressure switch), a flickering oil pressure light at tickover in a hot high mileage engine doesn't necessarily mean disaster.

Obviously the leak/crankcase pressure needs investigation too.

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Fixed it!

Turned out to be a dodgy oil pressure sensor so that was an easy fix. Now the panic has subsided its clear the oil leaks are old.

Worked my way through the breaker system for good measure and no blockages. Oil spray bar pumping out plenty of oil in all the right places.

Hideous fuel consumption likely down to the split distributor advance vacuum line as car feels much more lively now I've replaced that.

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