help me track down a suspension rattle

[slovakE70]

Originally Posted by arb

@LightlyToasted, is your rattle like this?
https://www.youtube.com/watch?v=jW6r4r3WL0s
https://www.youtube.com/watch?v=vVEh2y_wIuA

I spent 6 months about a year ago just like you. I replaced EVERYTHING in the suspension except the springs In my case, my front lower thrust arms failed a few months into their life. I had just replaced them so I started convinced it wasn't them. I replaced half the suspension, was ready to push the truck of the cliff, but before I did brought it to BMW. They charged me $700 to tell me to replace the other half of the stuff I hadn't replaced and were useless (later they gave me 300 bucks store credit back at least).
Eventually i got new lower thrust arms and that resolved the issue.
https://xoutpost.com/bmw-sav-forums/...ion-noise.html

I know exactly how you feel. It's terrible and I'm sorry for you right now, but soon you will be over it and then you can replacing your timing cover gaskets, valve cover gaskets, oil thermostat oring, valve stem seals, coolant pipe and valley pan just in time for the thrust arms to fail again...

I had exact same rattle as on the videos. I commented on 1 of those videos and the guy replied that it was front trust arms. If it was you then THANK YOU very much.

I replaced my with Lemforder and rattle was gone ! Before i even had wobble during harder braking.

Strange thing was that with pry bar i couldn't see/feel anny play or loosenes in ball joint nor bushing. After i removed right trust arm, i could feel small play in ball joint with hand. Bushing looked ok to me. Left trust arm looked all ok, but replaced anyway.

Funny how such a small play can create such a loud rattle noise.

But i still have some very small wobble when hard braking from 100 mph.

[ard]

Originally Posted by slovakE70

Strange thing was that with pry bar i couldn't see/feel anny play or loosenes in ball joint nor bushing. After i removed right trust arm, i could feel small play in ball joint with hand. Bushing looked ok to me. Left trust arm looked all ok, but replaced anyway.

Same issue on many cars. it is my suspicion that when the suspension is unladen (ie up on a lift, wheels hanging) that the thrust arms are loaded in a way that they just cannot be moved. SO it all seems OK.


My theory.....

[arb]

Originally Posted by slovakE70

I had exact same rattle as on the videos. I commented on 1 of those videos and the guy replied that it was front trust arms. If it was you then THANK YOU very much.

I replaced my with Lemforder and rattle was gone ! Before i even had wobble during harder braking.

Strange thing was that with pry bar i couldn't see/feel anny play or loosenes in ball joint nor bushing. After i removed right trust arm, i could feel small play in ball joint with hand. Bushing looked ok to me. Left trust arm looked all ok, but replaced anyway.

Funny how such a small play can create such a loud rattle noise.

But i still have some very small wobble when hard braking from 100 mph.

Yup, that was me on YT.
I also couldn’t detect a thing with the suspension on place. I was dreaming of rigging up a dyno with hydraulics to simulate quick bumps in the road before I just went for it and swapped the thrust arms.

[slovakE70]

Originally Posted by ard

Same issue on many cars. it is my suspicion that when the suspension is unladen (ie up on a lift, wheels hanging) that the thrust arms are loaded in a way that they just cannot be moved. SO it all seems OK.


My theory.....

I was checking trust arms at inspection pit, so suspension was at ride height and laden.

Your theory could be right. I think unladen suspension components probably can't show it condition as when laden.
So better checking at pit or wheel alignment lift, i guess...

[slovakE70]

To arb : I also couldn't figure it out. Then you said on YT it was the thrust arms. So i told myself - f*ck it, lets replace them and will see

And it solved the problem

[LightlyToasted]

Based on the recent comments, I've ordered a pair of Lemforder thrust arms and will replace them later this week.


If the bushing is indeed failing, what is causing the knocking noise? Is the thrust arm hitting the chassis? One post suggested that the outer and inner metal parts of the bushing were contacting, but I would think that would require the rubber to be so bad as to be easily detectable. If it is the chassis, I wonder if I could jam some foam or something between the two to see if it muffles the noise.

[slovakE70]

Originally Posted by LightlyToasted

If the bushing is indeed failing, what is causing the knocking noise? Is the thrust arm hitting the chassis? One post suggested that the outer and inner metal parts of the bushing were contacting, but I would think that would require the rubber to be so bad as to be easily detectable. If it is the chassis, I wonder if I could jam some foam or something between the two to see if it muffles the noise.

In my opinion if bushing is so bad that the arm is hitting the chassis, then you could easily detect it just by looking at it.

Like i said in my previous post, i had no noticable play in bushing nor joint when checking with pry bar. I found out that 1 ball joint had VERY small play when i pulled it/press it with hand.

It was making the same rattle/knocking sound as on the YT video.

[Badsmerf]

Originally Posted by LightlyToasted

Based on the recent comments, I've ordered a pair of Lemforder thrust arms and will replace them later this week.


If the bushing is indeed failing, what is causing the knocking noise? Is the thrust arm hitting the chassis? One post suggested that the outer and inner metal parts of the bushing were contacting, but I would think that would require the rubber to be so bad as to be easily detectable. If it is the chassis, I wonder if I could jam some foam or something between the two to see if it muffles the noise.

Any luck? I almost ordered some on the Memorial Day deal with Advanced Auto... hoping to get your feedback first.

[LightlyToasted]

I just finished replacing the thrust arms about an hour ago, but haven't gone for a test drive yet. Both bushings were fine, but the ball joint on the left arm had significant play. Since my knocking was from the left side, I'm hopeful that this was the cause of the noise.


Will take a test drive tomorrow morning and will report back.

[LightlyToasted]

Problem solved!!!


Clunk from tap braking, and rattle from stutter bumps is gone.


I checked my records, and I had replaced the tension struts / thrust arms less than 2 years and 14k km ago which is why I didn't suspect them. I can't believe the left ball joint wore out that fast. I can make it click by hand. The right ball joint, and both forward bushings were fine.



New tension struts are Lemforder from FCP, so if they fail again at least I'm covered for parts.


Time for a well-deserved pint. Wonder what's going to explode next....