[Tater.Gator]

Good afternoon and Merry Christmas! I was hoping to elicit some expertise from the group. I have a 2013 825i with approx 9000 miles that is making a noise that I hope to repair before it becomes a bigger problem. Under heavy acceleration, I hear what seems to be a belt slap from inside the clutch cover. When I leave off the throttle and reapply, the noise seems to go away. I am on my third belt in a two year period. When I last replaced the belt, I did notice an area closer to the primary that was beginning to wear through due to belt contact. i was hoping that the old belt may have been misshapen and had caused the issue. That seems not to be the case. A second symptom is that upon heavy deceleration, the machine surges a great deal via engine braking. i have been able to determine that the wheel bearings are ok, the transmission appears to be working appropriately, and i did just replace the front drive axle carrier bearing in that it failed. When i changed the last drive belt, i also replaced the wheels on the secondary clutch.

My working theory is that the primary clutch might not be functioning properly, causing the machine to engage/disengage inappropriately causing excess slack in the belt and the observed surging. Being the shade-tree mechanic that i am, this could be way off... Any advice from the group would be greatly appreciated before i begin the process of checking this theory out the hard way...

Thanks in advance!!

 

[Tater.Gator]

Tried to take a picture, but it didn’t turn out… an area just above the hose that leads to the intake above the cover for the belt is wearing through the plastic housing…

 

[Tater.Gator]

I have not checked primary rollers or weights, I did replace the secondary plastic rollers, but nothing else yet. Jd belt was used after cleaning surfaces and breaking in…

 

[Tater.Gator]

i had some time today to disassemble and take some pictures... i truly hope this helps diagnose the issue. What had caused this to be a problem was the noise i assumed to be belt slap. When looking into this further, I can see where the drive belt was hitting the cover...

The top of the belt had been hitting, but it didn't seem to have damaged the belt outside of when it came off, it was pear shaped, not oval as expected. I pulled the primary clutch out to inspect. I was able to notice some slide wear on the buttons, but the internal spring was intact, the clutch weights were ok and I could not identify any flat spots on the rollers.

Next, i removed the secondary clutch. The springs seemed ok and i had already replaced the rollers on the transmission side of the clutch. I did notice what appears to be significant wear on the outboard rollers in addition to wear on the metal surface of the outboard secondary clutch sheave.

my thoughts as a weekend mechanic is that the outer sheave and rollers are not operating properly causing the belt to extend and slap the cover.

I would very much appreciate other thoughts as I move forward!

Thanks!

 

[Tater.Gator]

So… I wanted to come back to share the conclusions of this journey. I sent the primary to the Clutch Doc to check out… a thorough clean and repacking of the idler bearing is all it needed. Paired it up with a new secondary and belt, then began the break in process. All is now working perfectly… the symptom I now recognize as a faulty secondary clutch was a belt slap under heavy acceleration and surging when decelerating…. Thanks everyone for your thoughts and support!!