Suppension Knock After Rebuild

[BUCK57]

Ok, I know this has been around since day one. 01 M Roadster (my 3rd Z, 97 1.9, 98 M, 01 M and my 9th two seater) So I've been around the block with Trimphs, MG's rebuilding you name it including my tricycle when I was 3!!

So here's my problem, Just finished replacing all bushing front and rear with Powerflex poly, B6 shocks w/mounts (front OEM, rear ECS ball bearing with reinforcment plate), gubio (installed properrly and pre load center drive shaft bearing), all sway bar links, new rotors and pads, bled brakes and clutch, change diff and engine fliuds/filters, belts. No subfarme damage on my garage queen I picked up 1/2017 all OEM with 53K and knew it needed work. Everything torqued to spec under load ecept RTAB that I torqued while the subfame was out knowing it's tight in there. And of couse there is a knock going over bums. Sounds universal from left to right like shock mounts or subframe. Shock mounts are fit flush and tight, no play. Gas tank and canister tight, I addressed them when subfarame was out with new rubber pad.

On smooth road no issues, tracks straight with no alignement yet and truns with no knock until a bump. I've jacked it up and visited eveyting twice pushing, pulling, checking torque, put a jack under this and dat to see if any play and I can find nothing lose or what is the culprit.

Any suggusts are appreciated because I'm thinking next step is drop subfame and reinstall???

Thanks

Steve

[Vintage42]

... On smooth road no issues... no knock until a bump... I can find nothing lose or what is the culprit...

A loose bumper weight (tuned mass damper) can make noise.
http://www.bimmerforums.com/forum/sh...6#post28785216

[BUCK57]

Thank you for the idea. It didn't make the noise before I started the project. The top of both rear OEM shock mounts were blown out and cliunked but not as loud as now. All the bushings looked decent but replaced anyways. I had no lose parts afterwards if you don't count beer cans. Maybe that was the issue, I didn't drink any while working on it.

Is there any access to stick a finger, screwdriver or something to see if the weights are lose. I've read some posts and didn't see any test procedure?



Thanks all

[khammack]

I'm guessing you have checked the obvious, but I'm going to point it out anyway. Verify all bolts are tight. Also check the rear body mounts for the sway bar. They are just spot welded and one of mine broke loose.

[kornfeld]

Any suggusts are appreciated because I'm thinking next step is drop subfame and reinstall???

Thanks

Steve

Wow, it would take me a mountain of troubleshooting before I went all the way to removing the subframe.

Here's a suggested process:

Begin by shifting your mindset. This sound could be caused by something you recently worked on, or it might not be related at all. It could literally be anything, so don't start by assuming it must be something you just worked on.

Next, gather more info. Get another person in the car to help you listen while you drive, or vice versa. Have them drive past you while you're standing outside the car and listen from the outside. Go over a speedbump (or whatever will cause it) slowly. Narrow it down to being only in the front suspension, only in the rear, or in both front or rear. You said it's "universal left to right," but did you try going over bumps that only hit the left tires, or only hit the right? Is it more pronounced when going over a bump forward, or backward, or is it the same in both directions? Can you get it to make the noise just by abruptly getting on the gas or brakes? All of these things should help hone in on the issue (or issues, because it could well be multiple things).

Next, assume it's something small. Search for a tool (like a loose socket or screwdriver) you left behind somewhere in the engine bay or tucked up on top of a suspension piece. Seriously, it happens.

Next, look for something else rattly that came loose, like the battery, or a brake caliper (did you recheck all of these?), or (as mentioned above) the bumper weight, or an interior trim piece, or something in the glove box.

After all of that I might consider putting the car back up on stands, and then jacking each control arm (or trailing arm) up one at a time so it's closer to the angle it would sit at while driving, then seeing if you can shake things and make it clunk.

I would need to have a reason to think it is the subframe in order to drop the subframe...I wouldn't do it as part of the troubleshooting process unless I had exhausted literally every option.

Jumping straight to the subframe seems like not a good next step, my friend. :

[BUCK57]

Good mornng kornfeld

Good advice that I have taken to heart and already done. It's frustrating to have done the work and expense only to have made a mistake. Oh the fun of having toys

[kornfeld]

I'm only able to give that advice because I'm not the one who just did all of the work. Believe me, if I had just finished that work and had a clunk after doing all of it (and I did do all of that same work over the course of the last year and a half), I would be ready to rip it all back apart again as well. It's good to have outsiders bring you back down from the edge.

[dbarton62]

BUCK57

Sway bar end links not torqued was my missed area

[BUCK57]

Well I went and did it. Jacked it up and stuff all over the place. Little piles and big piles. As it sits right now it's sitting on 8 pallets with 450 pounds in it. Everything looked good. No lose bolts or miss aligned components, no wear marks, NOTHING!!! So It's torqued to spec under load. Tomorrow, Jack it up, remove 450 pounds, remove 8 pallets and tidy up any lose ends and put the super sprints back on to see what it does. The bumper weights move from side to side as designed and are not lose. What a fun day!!!

Thanks for the suggustions

[Bryson]

Did you say you put in spherical bearing rear mounts? If they're not rubber isolated, I've never seen a set that doesn't clunk. No experience with this exact brand, but it's a data point for you

[kornfeld]

Well I went and did it. Jacked it up and stuff all over the place. Little piles and big piles. As it sits right now it's sitting on 8 pallets with 450 pounds in it. Everything looked good. No lose bolts or miss aligned components, no wear marks, NOTHING!!! So It's torqued to spec under load. Tomorrow, Jack it up, remove 450 pounds, remove 8 pallets and tidy up any lose ends and put the super sprints back on to see what it does. The bumper weights move from side to side as designed and are not lose. What a fun day!!!

Thanks for the suggustions

Did you do a driving test with someone else driving, with you in and outside of the car, yet? If so, what were the results?

I suggested that before lifting the car again because it involves the least work and can provide hugely useful information.

[BUCK57]

Bryson, regarding the shock mont, They are Mfg Part # 002542ECS01KT, ECS Part # ES#2762983, Polyurethane-isolated monoball design. They look nice??? So here I am online instaed of working on the M. Nice day here and I just might take the bike out for a ride instead as I know the M will be right where I left it!!! So if it still knocks time to try a different shock mount would be the simplest test????

Any recomendations on a good shock mount?


Ultimate Performance Rear Shock Mount Kit

Polyurethane-isolated monoball design
Ultimate Performance Rear Shock Mount Kit

Polyurethane-isolated monoball design

[Bryson]

It's tough to tell from the photos but essentially the thing you want is that the spherical bearing is 100% isolated from the metallic housing. This means both bearing shoulders and outer diameter should have some rubber, urethane, etc material in between to guarantee silent operation. I think the consensus is the OEM e46 M3 Cabrio shock mounts are the most reliable OEM option if you're considering OEM

[BUCK57]

I got it all back together and took it out for a nice drive. Fantastic sunset this evening from Pt. Vicente CA. Time to replace the shock mounts and see it that eliminates the knock. It's better than before but still a knock over some bumps. Seems the big bumps don't knock but the little ones do?????? I will say this, outside of the knock the car is on rails. Sign says 20 MPH hairpin doing 50 and no sway or tire squeel. The car is tight and handles so much better after the rebuild. It's drivable until I get the new shock mounts and find out if that is the issue. I get back and turn the lights off. Head lights go off but running lights stay on. Looks like time for a new headlight switch. I disconnected the battery. I just love this cage!!

[BUCK57]

I spoke with ECS customer service and they are sending me a new set of rear shock mounts no charge. Same mounts and if theres a problem give us a call. I asked for other type of mount and the Gentleman said we have had no issues with them and I'd be the first. Give the new set a try and call me ......... What can I say. They don't carry the Rogue Eng mount so if I still have an issue I'll buy the Rogue mounts. It's only $. ECS was great as they gave me a nice discount for placing a large order for almost all shocks, mounts, bushings and more for the rebuild. I'll continune using them. They have the new headlight switch but 3 days to ship plus transit time. I have it ordered from local BMW to pick up Wed for a few bucks more.

[BUCK57]

It's fixed!!! Solid rear end with no knocks, rattles or clunks. Thank you ECS for the new replacement shock mount at no cost. The old ones are in the trash. The rebuild was a success and very pleased with the results. For any of you thinking that you can't do a suspension rebuild you're either going to DIY or pay someone to do it. Best results for a project I have ever completed on a car. Your car needs poly!! Take my advice, you'll be glad you did!!

Now that the time has changed and warming up, time to go wear out the tires

[ECSTuning]

Glad my guys were able to help get you taken care of!

-James