Oil Level Sensor - Odd behavior

B

BadgerDog

Member
I know theres been much discussion about this frustrating sensor (seriously, my kingdom for a dipstick)...

However, I've been searching around this evening and have not come across anyone discussing the behavior I experienced. Wondered if anyone here had any brilliant ideas.

Went to see a movie this evening as a friend had rented out a theatre for his birthday. It was about 40 minutes away. When I was nearly there I got a notice from the car that the oil was low. "Crap," said I. Well, nothing to do about it right then.

Then I got in to go home. Watched for the oil level to be calculated again and lo and behold its just fine. Middle of the range. At first I chalked this up to a bad reading (car took it on a slope or whatever else). However, I noted that over the course of the drive home it started reading just a little lower... then a little lower... then a little lower. Until finally nearly home (same distance as before) it told me it was a quart low again.

So it seems that its reading lower over time, which is strange. I would think its related to temp, but Im certain that the COOLANT temp at least was stable long before it hit the 1L low point. I suppose its possible the oil temp was still climbing? Its a pretty mild temp out tonight, neither hot nor cold.

So, any thoughts? I've got a number of small, strange issues going on with the car I need to address (I think my battery is on its last legs), but this is certainly a new one.
 
I’d recommend getting the battery replaced ASAP as a failing battery can cause lots of issues with the E89, I’d probably put a little oil in as well just to make sure you are at maximum
 
A decaying battery can and often does cause all sorts of spurious faults / behaviour so IMHO that’s your first fix.

Oil level wise the sensor seems to always respond to scrutiny by varying around..

The best level deduction is after a long run..so since it’s said it low iafter a long run I’d take that value..

1 litre is the amount to add if it’s giving you a low oil warning..

Then having added that a 20 mile drive will show you the correct new value..
 
OK, thanks guys. I'm not certain the battery is dying, but have suspicions, and its certainly pretty old at this point. I'll top off the oil for now, then try to figure out where I buy one of these beasts of a battery around here (hoping most auto parts places can get them, but with my luck its some "ship from germany only" nonsense). I've got the ability to code in the new battery with ProTool at least.
 
Was it a good film? :)

Whilst in favour of electronic gizmos, among things that make me :roll: is no 2-bit, tried and true dipstick, and no easy means to put the 35is in neutral while off.

I’ve been reading (mostly here) that a faulty, old, low battery can cause heaps of misfires. Good to know this one as well. :thumbsup:
 
I think almost certainly down to oil temp variation between the two readings. Mine came up with low oil warning yesterday just before I got home, but driving to Halfords to pick up some oil this morning it said all was fine. Topped it up with 1L regardless and booked in for an oil change on Wednesday and a quick check over as oil level seems to have dropped quicker than I expected over the last week - not sure how accurate the oil level sensor is though, is it a purely analogue reading or more of max-mid-min indication (like most oil temp gauges)?
 
tiglon said:
I think almost certainly down to oil temp variation between the two readings. Mine came up with low oil warning yesterday just before I got home, but driving to Halfords to pick up some oil this morning it said all was fine. Topped it up with 1L regardless and booked in for an oil change on Wednesday and a quick check over as oil level seems to have dropped quicker than I expected over the last week - not sure how accurate the oil level sensor is though, is it a purely analogue reading or more of max-mid-min indication (like most oil temp gauges)?
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There was an article posted about the sensor and it’s logic..it’s actually 2 sensors in one plus some nifty logic..measures quantity and quality..

Had a lot more respect for it after that.

As they said if it says low then 1 litre should take it close to the top again,,

Cautions against ‘topping up’
 
Thanks Pbondar, I imagine the sensors are far more intelligent than I am! I don't completely trust the oil quality measurement - BMW are clearly very keen on a long oil change interval which saves them money, so I suspect the quality measurements will reflect that.
 
tiglon said:
Thanks Pbondar, I imagine the sensors are far more intelligent than I am! I don't completely trust the oil quality measurement - BMW are clearly very keen on a long oil change interval which saves them money, so I suspect the quality measurements will reflect that.
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I was suprised ..the sensor measures the acidity of the oil and deduces how shot it is..usually these things do a trend smoothed projection to predict end of service life..best to change every 5k or annually anyway!
 
I posted earlier having had the same issue. Only happened the once and when I checked it at the end of my journey and again the next day, all looked well.

Have a spare litre of oil now just to be on the sure side.
 
Marcoose said:
Was it a good film? :)

Whilst in favour of electronic gizmos, among things that make me :roll: is no 2-bit, tried and true dipstick, and no easy means to put the 35is in neutral while off.

I’ve been reading (mostly here) that a faulty, old, low battery can cause heaps of misfires. Good to know this one as well. :thumbsup:
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Back to the Future! So I'd say so, yes. First time I've been able to see it in a proper theatre which was pretty cool. Limiting it to 20 people you know is awesome, too.
 
Nanu said:
I posted earlier having had the same issue. Only happened the once and when I checked it at the end of my journey and again the next day, all looked well.

Have a spare litre of oil now just to be on the sure side.
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Must have missed that, but good to know I'm not alone. Working on the MG B today in prep for a little parade next weekend, but I'll turn my attention back to the Zed soon enough. Get the battery changed finally and then see which of the other odd crap goes away or comes back!
 
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