E90 Low Oil Pressure light on Dashboard

[Dan R]

Hi - The oil pressure light has popped up a few times over the last 12 months of having my 2011 318i (E90). It always happens when I come off a motorway and slow down for traffic lights, junction etc. It pops up, the car runs as perfect as always with no noise, knocking or anything and then when I turn the engine off and on again, it disappears as quickly as it came. 
 

it is a bit weird and a few mechanics have given different diagnosis (based on assumptions rather than looking at the moment). My usual Indy mechanic reckons if it was an actual real problem with my oil pressure then it would have destroyed my engine already and not continued perfectly over the last 12 months so reckons it’s a software issue but I thought I’d check here to see what people think.

it’s been a couple of weeks ago and this issue cropped up before and continues to do so afterwards so I’m positive it isn’t the oil filter etc.

so far, I’ve been told potential culprits are the oil pump, crankshaft and also possibly timing chain debris in oil sump with one garage reckoning around £1000 to fix, but with the car running no problem, I am reluctant to just hand the car to them with my debit card as it really doesn’t feel mechanical. I am however, NOT a mechanic!!

Any thoughts/ideas??

[Steve66]

My initial thoughts would be a sensor or the oil pump 

[SilverJohn]

Haven't been on the forum for a while so maybe this is too late, sorry, been busy with family stuff.

How often do you change the oil and filter? What's the mileage? If the car is getting to a higher mileage > 100,000, then maybe switching from 5W/30 to 5W/40 or even 10w/40 may help resolve this issue. Certainly oil pump may be the culprit if high mileage.

Hope this helps or maybe you already have the solution.

[Dan R]

Hi - Apologies, I haven’t been on here for a while. So I had a loose timing chain which one mechanic thought may be the problem as it drives the Oil Pump and therefore dropping pressure. Got that changed and then maybe a week later, light comes up again.🤦🏻‍♂️
 

Car currently has 68k on the clock so low mileage for an 11 year old car. It doesn’t ‘feel’ like the oil pump at fault as the car runs perfectly in every other way and as soon as I restart the engine, light goes off and doesn’t come back on. This fault has been occurring for about 12 months now (in my ignorance I thought it was low oil so just added a little too up previously)and car is fine. Runs like a dream, just this light. I am going for a sensor change next to see if that works - as soon as I get paid that is as the Timing chain was £460 and I also needed new Brake discs all round last week so a pricey month!

The light still only comes on after I come off a motorway after a few miles and pull up at lights etc and slow right down to a stop. Ill post an update once my sensor has been changed and tested to keep you updated.

[Greydog]

Hi Dan

Is the car running the correct oil ? Is the oil level correct ? If yes is the answer to both questions it could be a sticking pressure relief valve in the pump there is another in the oil filter cap or a dodgy oil pressure sensor. The fact it seems related to motorway driving and then slowing down sounds like low oil level.

I would first flush the engine to clean any crud from the system refill to the correct level with the correct oil plus new filter and oil filter housing cap. Changing the pressure relief valve in the pump is a sump off job so fingers crossed not that one.

Dave