Oil Pump Backlash

[SilverDust]

Ok guys,

So I took my '12 in because I have the platinum extended warranty and the engine has started to make a whine that I didn't like. I figured it was just a pulley and would be no big deal. I get a call a little bit later from the SA saying that the oil pump has "backlashed" aka skipped a gear tooth and needs to be adjusted to be fixed. $2300 not covered under warranty.

My questions.

1) Is this "backlash" explanation plausible? Has anyone else heard of this?

2) If this is actually a thing, how could I work this to be covered under the warranty? I have read through the contract it lists "adjustments" as uncovered.... so if i drove it till it breaks, then I'd be covered as the oil pump is not listed as uncovered.

Y'all's thoughts? Thanks in advance for any insight

[SYT_Shadow]

I have never heard of this... lets see what others chime in

[eddunn]

I think it is somewhat implausible that it would skip a tooth without something else happening, i.e. excessive guide wear. I haven't had one apart to know if there is a clocking feature, my guess is no, because it is driven by a chain from an idler gear off of the crank.

[Green-Eggs]

The oil pump is not keyed or timed to the rest of the engine. Even if it skipped a tooth (which probably would cause other issues), that itself doesn't need an adjustment to put it back -- because there is no putting it back.

[Richbot]

I want to know how they figured this out without dropping the subframe and oil pan first. Must be magical X-ray vision at that dealer

[Doc Oc]

Take it to a new dealer....

[SilverDust]

Originally Posted by eddunn

I think it is somewhat implausible that it would skip a tooth without something else happening, i.e. excessive guide wear. I haven't had one apart to know if there is a clocking feature, my guess is no, because it is driven by a chain from an idler gear off of the crank.

Hey guys!

Thanks for the reply's! So to update, Eddunn, I was right with you on it. I have a Mechanical Engineering degree and spent a whole lot of time in school working with our Formula SAE team. I'd never heard of gears skipping without something else happening (wear, broken tooth, etc)- and then "adjusting" them back wouldn't fix the issue.

Once I had a starting point (oil pump) I did some digging and found this thread: http://www.m3post.com/forums/showthr...p+whine&page=2

My car sounded almost exactly the same, and I used Juicehead's experience to get them to cover it. I explained it all to the SA and the Shop Manager and after a detailed discussion and explanation they agreed to replace the whole oil pump system under warranty.

Originally Posted by Richbot

I want to know how they figured this out without dropping the subframe and oil pan first. Must be magical X-ray vision at that dealer

So they showed me how they determined the issue using some software developed by BMW (the SA said it cost like $500k+). Via the OBD-II port they hook up and start the engine. Then with this software taking readings, they rev it a few times and describe the issue in a search box in the software ("whine, front of engine, etc").. After following a trail of questions about the issue, it then pops up with probable causes and a video, with sound of the cause. In my case, the sound was identical to the one my car was making.. Add that to the thread from Juicehead and I agreed with them.

It was a fascinating diagnostic tool. And even with some of the coding experience I have had with our car, it just further showed me how digital this car is. There are sensors and monitors everywhere. Coming from a import background, the German's are just on another level.


I'll let yall know how this shakes out and if it really fixes the issue. I'll also try and speak to the shop guys again and see if I can't get a better explanation on what "backlash" is and how it is measured.

[Richbot]

Fascinating tool which appears to have failed to work properly if it told them to adjust it. Wtf?

[SilverDust]

Originally Posted by Richbot

Fascinating tool which appears to have failed to work properly if it told them to adjust it. Wtf?

Forgot to mention that part. Yeah so in that discussion about what was going on, the Shop Manager explained that the "adjustment" was part of the installation process of a new pump drive gear. When the SA originally called me to tell me about the $2300 in uncovered work, the Shop Manager had only mentioned the adjustment to the SA and not that it would require new components.

When the three of us talked, he showed the SA and I the work instructions on that software which called for replacing the oil pump drive gear and "adjusting" the backlash. I showed them Juicehead's post and all that. Once the SA saw that it required replacement of parts, he was all about getting it done under warranty.

As a tool, it was pretty impressive in diagnostics. The tech didn't have to tear open the car to determine what the issue was. Assuming this is what's actually causing the noise on my car.

[GMWNashville]

What they are likely stating is the issue is the gear to gear connection of your primary oil pump. That pump as you can see from the above picture is then chain driven to the second oil pump. The timing of either doesn't matter as they don't have any but the clearance for the gear to gear connection with your crankshaft is very important.