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      08-23-2018, 12:09 PM   #1
Andy198712
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Chasing a knock,need ideas

Hi,

Got a 2010 E91 325d N57 LCI
Itís on 80k miles.
Non run flat tyres

I noticed a knock when the front left wheel went over bumps at slower speeds which started to get worse, at first thought it sounded just like a loose bush/ ARB link, that sort of hollow metal ish rattle/clunk

Got the car up on a two poster and could feel no play in the wheels in any range of movement.
ARB links felt solid, Sus links felt fine, nothing appeared loose.

I did notice a worn ARB bush in the left front with witness marks on the bar and cradle. Changed that yesterday and thought Iíd cured it but sadly not.

Any thoughts or ideas to check?

Cheers
Andy
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      08-23-2018, 12:59 PM   #2
wallsmk2
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As you say, it could be anything. Sometimes when the wheels are hanging in the air, it can be hard to tell where the play is. I would first do the drop links as they're cheap and easy to do. They'll be about £20/side this bank holiday for lemforder at ecp. Tie rods can cause a bit of clunking so I would look there too. The thrust arms and upper control arms I've not heard clunking until they get really bad and then I'd think you would hear under braking etc but you never know. Then check for any play in the strut - it may be a worn top mount or there could be play in the strut piston rod. I had some play in a bilstein rod and it made quite a noise at low speeds on rough roads.

Good luck!
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      08-23-2018, 01:38 PM   #3
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Take it into your local STS, Kwikfit etc & have them do a free suspension check, they may have a shaker lift which shakes the car around whilst a chap looks underneath for issues.
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      08-23-2018, 05:22 PM   #4
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All of the above plus check the coil springs are not broken.

To be fair BMW's are not as bad as some other manufacturers for this but it does happen sometimes. I had to replace springs on my Z3 because the bottom coil of one of the rears had snapped off.

The breakage can be difficult to spot and you really need to get good light under there and prod and poke about with a screwdriver but it seems you have access to a lift which simplifies matters considerably.
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      08-23-2018, 05:31 PM   #5
Andy198712
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Cheers guys,
I did have a good look at the springs but will look closer, although one thing I did note when changing the anti roll bar bushes, the driver size would push onto the studs okay
But the passenger side which I think my clonk is coming from took loads of effort to push up, needed a trans jack.
No matter if I did that one first or not (I tried a few times)
Maybe I need to inspect it more....

Never knew about the shaking table will look into that chappers


I first thought links but just holding off changing them as I doubt theyíll be as good as oem, sounds silly I know lol
Iíll inspect the shocks more, do plan to change them in the next 20k miles or so, birds setup looks nice.... £££
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      08-24-2018, 01:23 AM   #6
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ice got one,,more of a rattle/knock,,eeven sounds a bit plasticky,,had it on shaker plates etc and nothing,,i also have a slight steering wheel wobble when braking,,ive got all arms for front and gonna invest in some new discs(zimmerman) and some yellowstuff pads...sick of brake fade when pressing on and doing a few deceent speed braking sessions..
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      08-24-2018, 02:53 PM   #7
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Double checked the springs today by running my fingers along them and felt and looked fine.
I did measure a 5mm height diff either side but could be anything including floor

With the bonnet up I rocked the car firmly (wheeey) and I replecated the noise I think (hard to tell being outside the car hearing it vs inside) but was in my own so will have to get a mate to rock it while Iím under it on the lift looking around!
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      08-24-2018, 03:04 PM   #8
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Quote:
Originally Posted by Andy198712 View Post
Double checked the springs today by running my fingers along them and felt and looked fine.
I did measure a 5mm height diff either side but could be anything including floor

With the bonnet up I rocked the car firmly (wheeey) and I replecated the noise I think (hard to tell being outside the car hearing it vs inside) but was in my own so will have to get a mate to rock it while Iím under it on the lift looking around!
All the e9xs sit lower on the drivers side, BMW made them that way to compensate for the weight of the driver on lhd cars & they couldn't be bothered to change it for those of us that drive on the correct side of the road.
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      08-25-2018, 03:56 AM   #9
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Ah! Well there you go
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      09-11-2018, 12:12 PM   #10
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so to follow this one up, put it on the ramp again, this time weight on wheels, poked around and only thing i can feel is the lower control rods move slightly on their rubber bushings but only what i could call, normal movement for a rubber bushing, not play and thats being super picky.

when i bounded the car from under it by hanging on the roll bar and pulling down to bounce it, i heard a clunk from the right hand shock are (bear in mind it sounds like its from the left in the car, and its mostly when going over bumps on the left)

so took the car off the ramp and jacked up the front right wheel an inch, put a pry bar under the tyre and moved it up and down then. i can feel a bit of play i'm sure, and it looks like it may be top mount.

if i slide my hand up past the spring and onto the metal at the top and lever the wheel up and down i can feel movement up there, id say more so on the right and to a lesser extent on the left, BUT this is a rubber bushing with the bearing mounted in it isnt it so.....

but my gut feeling says it could be the top mounts as it just doesn't feel right.

i tried the 3 mounting bolts either side and they were tight, and popped the cap off and both big nuts had the same amount of thread showing.


i'm thinking change the top mounts and go from there, at 82k on what i think is the original its not too much of an issue.
was going to wait till 100K to treat my self to a BIRDs setup, just can stretch to that at the minute (unless it turns out the shock is tits)

going to go with the Lamforder brand as people say they seem to be OEM or close to.


would that cause my knock? i don't get clunking on steering when slow or stationary which would normally be knackered top mounts and springs are intact (checked again)

I'm happy to start working through suspension parts anyway as it has some miles on it.

oh i changed the roll bar bushes as they were worn and it did tighten the handling (febi brand) which was nice but didn't heal my knock.
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      09-12-2018, 01:13 AM   #11
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Quote:
Originally Posted by Andy198712 View Post
so to follow this one up, put it on the ramp again, this time weight on wheels, poked around and only thing i can feel is the lower control rods move slightly on their rubber bushings but only what i could call, normal movement for a rubber bushing, not play and thats being super picky.

when i bounded the car from under it by hanging on the roll bar and pulling down to bounce it, i heard a clunk from the right hand shock are (bear in mind it sounds like its from the left in the car, and its mostly when going over bumps on the left)

so took the car off the ramp and jacked up the front right wheel an inch, put a pry bar under the tyre and moved it up and down then. i can feel a bit of play i'm sure, and it looks like it may be top mount.

if i slide my hand up past the spring and onto the metal at the top and lever the wheel up and down i can feel movement up there, id say more so on the right and to a lesser extent on the left, BUT this is a rubber bushing with the bearing mounted in it isnt it so.....

but my gut feeling says it could be the top mounts as it just doesn't feel right.

i tried the 3 mounting bolts either side and they were tight, and popped the cap off and both big nuts had the same amount of thread showing.


i'm thinking change the top mounts and go from there, at 82k on what i think is the original its not too much of an issue.
was going to wait till 100K to treat my self to a BIRDs setup, just can stretch to that at the minute (unless it turns out the shock is tits)

going to go with the Lamforder brand as people say they seem to be OEM or close to.


would that cause my knock? i don't get clunking on steering when slow or stationary which would normally be knackered top mounts and springs are intact (checked again)

I'm happy to start working through suspension parts anyway as it has some miles on it.

oh i changed the roll bar bushes as they were worn and it did tighten the handling (febi brand) which was nice but didn't heal my knock.
i suspected top mounts,,but as you say,,when stationary i get no sound when moving steering wheel..my rattle/clonk is quick when going over course gravel/dolomite..i only seem to hear i t when going slowly,,that is what leads me to think top mounts,,driver side mpunt has noe cap on it and the inside looks a bit dodgy,,will wait and see if it develops
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      09-12-2018, 04:21 AM   #12
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A little unrelated perhaps but an indication of how difficult these sort of noises are to track down.

Back in the day when I had a Jaguar XJR I spent many hours and a fortune replacing all of the bushes, dampers, mounts, links, bells and whistles on the rear suspension and still the noise would not go away. I even had the diff rebuilt!

One day I was right underneath the car doing something totally unrelated like a fuel filter or something and I accidentally leant against the gearbox which moved about 2". Referring to my Jaguar Daimler Heritage Trust Manual, how I wish other manufacturers would make comprehensive manuals like this available to mere mortals, I noted that the gearbox had a coil spring over damper type arrangement as a tail mount. Upon investigation it turned out that the damper was almost non-existent and the whole gearbox was bouncing around on a coil spring unchecked. I ordered the parts, fitted them in about half an hour and fixed a problem that had been unresolved for several years. The car suddenly became so much nicer to drive!

Moral of the story is that your problem is likely to be a suspension component but do not rule out the possibility it could be something else.
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      09-19-2018, 05:34 AM   #13
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I had the front left top mount on my e91 go bad quite quickly. You could hear the knocking while driving normally and it was so loud you could hear it above the radio!

Ended up changing both front top mounts and although the bearings are mounted in a rubber bushing they were so bad you could tilt them side to side

Fitted the new top mounts and there was no play and it cured the horrible knocking I had.
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      09-19-2018, 07:07 AM   #14
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Quote:
Originally Posted by bishbosh View Post
I had the front left top mount on my e91 go bad quite quickly. You could hear the knocking while driving normally and it was so loud you could hear it above the radio!

Ended up changing both front top mounts and although the bearings are mounted in a rubber bushing they were so bad you could tilt them side to side

Fitted the new top mounts and there was no play and it cured the horrible knocking I had.
was the knocking like this,,if going over say pebbles,,did the knock quicken up as suspension went up and down,,and did it sound non metalic?
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      09-19-2018, 12:14 PM   #15
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Originally Posted by rasa bmw View Post
was the knocking like this,,if going over say pebbles,,did the knock quicken up as suspension went up and down,,and did it sound non metalic?
In my experience the first sign of worn front top mounts is a creaking kind of a noise whilst slowly manoeuvring.
My local BMW dealer told me top mounts would unlikely be the cause but I changed them anyway & the noise went away.
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      10-11-2018, 01:10 PM   #16
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top mounts are now done and did the drop links at the same time, one top mount had play, other wasn't too bad but bearing wasn't so smooth.

drop links, one had play in one end, and the other had a slight bend in it!

anyway, i "think" its now sorted but will know better later after a longer drive on less then smooth roads!

fingers crossed
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