Rod Knock Gone After Replacing with BE Bearings | Old Bearings Fine

Hey guys,
I am just sharing a recent experience. I had a 'heavier' metallic knocking sound when the car was warm and I would pulse the throttle to 1K and 1.5K.

The car is a 2010 with only 15K, but I recently installed a Harrop Supercharger, so I took it straight to the shop to have it checked out.

Mike at BPM Sport supplied the BE bearings and rod bolts and the team at Performance Technique (PT) in Fremont, CA did the work. Joe and the team at PT are outstanding and the work was fast and clean.

Long story short, my old OEM rod bearings were fine. The tech (Kendall, cool guy) did note that the old bearings were loose in the journals and dropped out upon dissassembly.

The symptom noise is now gone though and I have been running for ~800 miles since.

I thought I would share this unique experience of a knocking noise with bearings in fine condition.

If anyone needs this work done in the bay area I highly recommend Performance Technique in Fremont, CA. I am a mechanical engineer and I typically do my own work, so it is hard for me to trust shops, but PT came well recommended and they exceeded expectations. When I got the car back I could not even tell a single bolt was removed and the car drove flawlessly. Thanks Joe and PT Team!

Special thanks to Mike at BPM Sport for jumping through hoops to get me a set of BE Bearing and bolts in time!

I'm pretty sure I sure I saw your car in the shop recently. Glad you got the problem solved!

👍 this is the car

Nice, I need to hear how loud that whine is one of these days.

those bearings are already starting to show some wear for 15k. if you had 100k on the car, we'd talk more, but at 15k, the wear isn't great.

What was the oil before and after the service?

Any chance that you were hearing valve or other drivetrain noise, usually a clicking sound, and changing the oil got rid of that noise?

It seems normal for some oils to be noisier than others.

My car seems to make noises at the RPMs you described but I try to quell my fears and just accept that the S65 is a noisy engine.

I will guess the sound was not rod knock. Your bearings would show it if you had it. But whatever it was, it got fixed as a result of the car being taken apart underneath and put back together again. Time to start driving the car. 1.5k miles per year is not much.

Definitely wasn't rod knock or bearing related but hey at least the noise is gone.

This may be one of the most interesting cases yet!

bmwlover0725 wrote

This may be one of the most interesting cases yet!

Nope sounds like a misdiagnosed noise.
It can't be rod knock, if there is no play in the rod assembly to cause a knock. The noise has to come from somewhere.

tdott wrote

Nope sounds like a misdiagnosed noise.
It can't be rod knock, if there is no play in the rod assembly to cause a knock. The noise has to come from somewhere.

It’s valve noise, common at those RPMs, and usually solved by a flush or new oil. Wish this forum wouldn’t promote so much hysteria around these rod bearings. Just because they wear doesn’t mean they’ll seize or spin anytime soon.

At least this mania has led to awesome prices on the secondary market.

https://www.m3post.com/forums/showthread.php?t=1167323

https://www.m3post.com/forums/showthread.php?t=1418410

#3

It’s not mania. Educate yourself by looking at pictures of bearings that come out of these motors. About 90% look bad.

https://www.m3post.com/forums/showthread.php?t=1253084&page=48

It could have been valves, but it had a heavier sound which was most audible near the driver side wheel closer to the ground. I will try to upload a video of the before condition.

doogee wrote

Definitely wasn't rod knock or bearing related but hey at least the noise is gone.

This...

The tabs do look fairly worn. It's probably good that you had them replaced even though the wear isn't too bad.