BMW 335i Low Oil Warning vs Sensor

[blackgrape]

I have a yellow low oil warning light.

The car has just been serviced, and filled with oil. This light comes on after 20 minutes, and when the car is stopped. The car had been on a car transporter and may have been shipped on an incline.

So, it seems unlikely it is an oil problem if it has just been filled. They found no oil leaks when I had the car inspected last week. There were no fault codes on the diagnostics.

Do you think this is a faulty sensor?
Or something to do with the way the car was shipped causing a false reading?
I would add more oil, however I've read that over-filling with oil is not a good idea.

Your thoughts? How would I determine the cause? There doesn't seem to be a way to measure the oil level, apart from using the electronic reading, which relies on the sensor, of course.

Oh for a simple dipstick!

 

[Torn Mind]

Lol, no dipstick is to satisfy the many "sophisticated" buyers who thinks that we have "advanced" to electronic monitoring. But a dipstick is reliable on a level or near-level surfaces and cannot malfunction. Poor fellas seem to forget that technology helps us do things, not slow us down. The dipstick will always be the superior tool.

My totally uninformed guess is the sensor, but yeah, I don't know Bimmers.

 

[XavierMace]

While I agree no dipstick is silly, when I got the first low oil light on my 135i, I did some research and couldn't find any reports of the sensor failing. It's possible it wasn't completely filled the first time. The light comes on when it wants you to add a quart of oil in a 6 quart system. By the sound of it, you're only getting the light intermittently? How long have you been getting it?

 

[blackgrape]

It goes on around 20 minutes after driving. I can cancel it and it doesn't come on again until I stop the engine.

They said they filled it with oil and did a full service
Didn't see any errors from diagnostics
Put it on a truck
Sent it to me
Happens each time I drive it

Dealer - who is not in the same city, else I'd just take it back - thinks it's likely a false reading on the sensor, but contact him again in a few days if it persists. I'm trying to see if it's possible to troubleshoot before then, but if I add the stated oil, will that cause damage from having too much oil?

 

[Railgun]

A yellow warning isn't the end of the world. You're a quart low IIRC, which is fine for most normal driving. I'd take it back to the dealer or add a half quart to see if that fixes it. A half quart isn't going to hurt it.

 

[boomerang]

http://forums.anandtech.com/showthread.php?t=2437781

 

[Mutilator]

While it's possible the sensor is bad it'd actually be at the bottom of the list for me - my 135i electronic gauge is like clockwork as far as oil level/consumption goes even as I approach 100K miles. Much more likely is they simply didn't actually add any oil, or not enough if they did. At least you didn't say they did an oil change. Either way, only way to be sure is to drain the oil, see how much comes out, then put the correct amount (of new oil) in. And change the filter while you're at it. If things don't add up then I'd probably find a new place to have my car serviced, or do it yourself if possible.

 

[Railgun]

http://forums.anandtech.com/showthread.php?t=2437781

And?

That thread has no bearing on the N54/N55.

 

[blackgrape]

Thanks Guys.

So, I might test this way:

- add 1/2 the specified amount (approx 1/2 1 litre). This won't damage the car? Test.
- if that doesn't work, drain oil and measure physically. I take it there is no other way to physically measure the amount of oil?
- if those don't yield results, take to dealer. Likely faulty reading or oil leak somewhere, although the latter seems unlikely as it has just had an oil change. Warning light appeared on first drive following oil change. No error code recorded prior to this service or transportation. No signs of oil leaks during inspection.

"At least you didn't say they did an oil change"

Sorry, it has just had an oil change and service. Dealer in another city, so I trust what he is saying is the truth. There is an oil sticker on the windscreen specifying same.

 

[blackgrape]

Ohh...kay....

So, added 1/2 litre. Reading hasn't changed at all.

Starting to assume the reading is wrong? Surely it should have gone up?

 

[Mutilator]

In my 1 when I get the qt low light and add 1 qt it goes from the min line to the max line.
Consistently burns 1 qt every 2500 miles.
As for 335 specific stuff you may be better off @ http://www.e90post.com/forums/index.php rather than here, probably get more responses faster.

 

[tracerbullet]

The engine will take about 7 quarts, quite a darn bit, so adding 1/2 quart might be w/in the threshold of the meter not really saying it's sensed a difference. Not exactly a super calibrated device.

You are correct that overfilling is a bad idea, if it's so high the crankshaft spinning around hits it you might do some interesting things.

Was it a BMW dealer or like a used car dealer? There's a chance they didn't fill it enough if they don't know the car well.

I'd consider draining and refilling the oil, to be sure it was the right amount. or replacing the sensor. Whichever is less expensive since it seems 50/50 at this point. I want to say the sensor is in the pan and not that big of a deal. How "mechanically inclined" are you?

 

[blackgrape]

Thanks Tracer.

Not mechanically inclined. I quite like working through the problem, however, but I need you guys to help correct my thinking if I'm missing something.

I take your point that the threshold of the meter may not have sensed a difference. I guess I don't want to keep adding to see where the threshold is, as this may result in too much oil, and cause different problems.

Used car dealer, not BMW. They did plug it into BMW diagnostics though, and it showed no errors. Car also had further independent inspection, and they found no leaks from visual inspection. Compression test fine, if that helps.

Is it difficult to drain oil out? Never done it before.

 

[blackgrape]

BTW, if I wanted to become "mechanically inclined", how much work can a lay-person do on these cars? Aside from these forums, any good books you can recommend? Tool requirements?

 

[SOFTengCOMPelec]

Redacted

(An earlier post, had a better answer.)

 

[XavierMace]

I highly recommend picking up a cable so you can check the data yourself. I've got one for my 135. Just reset some codes over the weekend after wrenching on it. But yeah, 1/2 liter isn't enough to make the light go off. Light goes on when you need to add 1 full liter.