Knocking noise in front suspension

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Tierfreund

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Hello all

I have a problem with my front (most likely left side) suspension. I have a nasty knocking noise when going over a bump or pothole with the left front wheel. More prominent when the front left is loaded (fast right-hand cornering), more likely if the bump/hole only hits the front left, less likely if both sides are going up or down.
The noise first came when I hit a very deep pothole this winter.

History:

- All rubber on the chassis was replaced 3 years (60.000mls) ago.

- Replaced the front and rear shocks and springs 3 months ago (makeing the sound more prominent)

- Replaced the wheel bearings on all 4 corners 2 months ago (checked and rechecked the front bearing clearance several times)

- Had the car checked for road-worthyness (german TUEV) where front supension was checked (they put it on sort of a horizontal shaker and check for play in the bushes). Nothing found.

- (Visually) checked all front suspension components several times (including fron anti-roll-bar and it´s rubbers. Found some slack in the anti-roll-bar coupling rod nuts, tightened - to no avail)


Plan:

As they are inexpensive and easy to change, I´ll be changing the anti-roll-bar rubbers this weekend, but I have little hope that´ll fix it.
I´ll also take the front struts apart again and will check everything there (maybe the big nut that holds the front shock in the strut).

Any suggestions / any ideas?

P.S. This is on an E3, but I believe the front suspension to be identical to the E9 and this is the most knowledgeable crowd I know.
 
Check that the large "nuts" holding the shock absorber cartridges are completely tight. If not, the strut cartridges can move in the strut and make a banging noise.
 
Sounds plausible. Had quite some trouble getting the nut off when I changed the shock. The thread may be dirty / damaged.
Will take apart, check and post the outcome.

Thanks
 
This happened to a fellow coupe owner a few years ago.

It ended up being the gas strut moving up and down inside the strut assembly. A simple tightening of the large nut holding the cartridge in place worked fine. We did remove the entire assembly for this process but you might not have to if you can access through the springs.

Good luck.

Thanks,
 
That was me. Some how the large nuts holding the strut cartridge in worked them self loose. It was really pissing me off. I pulled (with Shawn's help) the springs off and re-torqued the nut with a special wrench I got when I bought my first set of Bilsteins. You might be able to use a screw driver and a hammer to drive the nut tighter to test our theory without taking off the struts
 
Strut Cartridge Oil

On the same subject, there were a few ounces of oil in my strut tubeswhen I replaced the inserts a few weeks ago. I noticed that RealOEM indicates that there is oil intended to go with the inserts so I replaced the old stuff with some gear oil before putting the new shock inserts in. Does the oil help to dampen the rattling? Does it just keep the insert from seizing in there forever?
 
The handbock says to put in 30ml of SAE30 to help heat distribution.

But that probably applies more to the old oil-based shock absorbers. Not sure if more modern gas-based unit still needs it. I did fill in the oil when changing the shocks (even though they are gas) and might have put in too much (thereby hindering the shock in getting in all the way, then giving me a problem with tightening the nut). I´ll take apart on Saturday and post the results.

The oil certainly did not prevent the knocking (I don´t think anything on a suspension is ever meant to knock. Knock indicates play or undue contact and thereby undue stress on components and danger. I don´t think they´d use oil to prevent the noise...)
 
This happens to me periodically and the tightening of the nut does help, but it tends to loosen again over time and it is a PITA. I was wondering if it has to do with fitting Bilstein sport shocks --- are they too stiff for the E9 application?
 
I had the Bilsteins before and a nut that had rusted tight. No problems :)

Maybe I need to spray some saltwater or acid on the nut and then (over-) tighten it. :mrgreen:
 
Sloppy rotation, dry bearings, up and down or yaw movement, visual inspection shows damage to the ball bearings, cracked broken rubber.
2 main symptoms of bad strut bearings that I see are hard steering/ poor return to center and noise from under the hood while going slowly over bumps.
 
Dry upper strut bearing

When I removed the struts 4 yeas ago on my new bought E9 (garage sleeper since 1980) I noticed the upper strut bearings were totally dry. No sign of grease or oil!

That I found very strange and thought the bearings was lost despite of they felt rather tight in clearance .

Anyway, I cleaned them up and filled them with grease and they were remounted.
To my relief they still works.

I wonder what kind of grease or oil that was put in the upper strut bearing from the beginning and how it could totally vanish over the years.

Anyone with similar observations?

Tierfreund, perhaps with a raised front and with for example a large crowbar affect the strut and at the same time observe the upper strut bearing. A loudly clearance is often also an visible clearance.

Best luck
//Stefan
 
An update. Issue fixed, but not sure why

A little update:

Step (weekend)1:
Took the struts out and apart (again) to look at the nut that holds that shock in the strut. The one on the left strut would not go all the way in so I replaced it with a new one that I had ordered (and that fit nicely). Might be that the nuts I had on the struts we´re not the right ones in the first place (I had Bilsteins in before, went to Boge Gas Struts now). The new one fit like a dream. Put it all together and some loctite on the thread. Found that the nut on the right strut, was in even worse shape. It had actually split and didn´t have much contact area with the shock anymore. Since I, the cheapo, had only bought had one new nut, couldn´t finish the job (bugger). Put everything back together.
Car still had the problem

Step (next weekend)2:
Got another new nut and some new rubbers for the anti-roll-bar. Took the struts out and apart (again), replaced nut on the right strut, Now both shocks were really solidly held by the right and proper nuts. Looks splendid. Should never give problems again.
Replaced the rubbers in the joints holding the anti-roll-bar on the front subframe. Tried to replace the rubbers on the anti-roll-bar links but since the bolt and hollow bit were severely rusted tight I could only replace the lower rubbers
Put everything back together, drive car, clunking noise still there
BUGGER

Thinking phase (that´s a first, I usually skip that):
Since I have to rent a garage space with a lift each time I want to work on the suspension and I don´t want to spend EVERY saturday under that lift, I decided to ditch the scientific approach of changing one part at a time and went to the dealer for a bigger order.

Got new:
- Uper strut bearings left and right (expensive)
- all washers, nuts, other parts that somewhoe belong on and in the vincinity of the front struts / mounts / etc. (had seen some quite badly bent and beat up washers/pieces /reinforcement pads on the shock/uppershock bar.
- new anti-roll-bar linkage parts (bolt, nuts, washers, hollow thing (tube), rubbers)

Step (weekend)3:
Took front struts and anti-roll-bar out and apart (AGAIN). Needed an iron saw to take the anti-roll-bar linkage apart
Cleaned everything, put it all back together with the new parts as best I could with the help from the blue books
This time, I don´t use an impact wrench to tighten the shock absorber rod nut (that goes through the upper strut bearing and holds the whole strut shebang together). Instead I used a big crooked spanner for the big outside nut and a smaller socket and wrench to hold the rod. I figure, maybe i`m bending / breaking stuff with the impact wrench.

Put everything back together, drive car:

HURRAY!. No more clunking noises.

Two problems:

1. I really don´t know what the problem was.
2. I took a few pictures with my mobile to show here. But before I could transfer them from the phone, I drop it, break the glass, try to replace it, break the phone for good, get a new one, have no pictures. Sorry.
 
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