The strangest body noise and vibrations
 

Hi all, after recently getting my 85 380se to idle properly, I've been confronted with a new noise coming from the front right wheel well and general vibrations at higher speeds.

the vibrations first: I can drive the car around town up to about 40 mph. I can accelerate all the way up to about 75 mph on smooth road with generally no trouble. However, the minute I hit a rough spot in the road or I have to tap the brakes, I typically get a strong vibration through the steering wheel. I've already suspected unbalanced tires. I've taken them to the discount tire where I purchased them originally and had them rotated and balanced. I suspected shoddy balancing and took them back and they rebalanced them.

After the second go with balancing, I still get vibrations starting at ~45 mph and they can last up to about 65 mph. Vibrations can also now start anywhere above 45 up to about 65 mph. Could it still be a balancing issue? What could explain the fact that the use of brakes generally starts uncontrollable vibrations?

I read on another post created recently a response that listed out a number of possibilities having to do general vibrations. I get a strong feeling (quite literally), that the source of my vibrations are coming from the wheels but I can't quite figure out how. I distinctly remember the day they all started; I was driving out of my parking lot and I hit a huge deformation in the road doing about 45 mph. Since then I've had the brake pads changed and I don't recall the rotors being anything but smooth.

The body noise: Sometimes when I'm pulling out of my parking spot in the morning, I'll reverse and apply the brakes to stop and put it in drive. At the point when I put on the brakes I generally either stomp on them or ease on them.

In the case of easing on the brakes in reverse, I don't get any noise.

In the case of stomping on the brakes to stop the car in reverse, I often get a loud thud noise from the front right (I think) wheel well. What could that be? I had the front suspension completely rebuilt about a year ago which makes me think that something might be loose; perhaps a guide rod linkage, or an upper sway bar bolt, or an upper control arm bolt? The thought's also crossed my mind that maybe its a worn wheel bearing slopping back and forth, but that'd be a bit extreme wouldn't it?

At any rate, I appreciate your advice in advance,

-Troy

Wheel bearing are easy enough to check. Grasp the tire at the 12 and 6 o'clock positions and attempt to rock the tire. If you feel any play, the bearings are loose and need to be replaced. Also, rotate the tire by hand. Any roughness or noise from the bearings would also tell you the bearings are worn or damaged and need to be replaced.

Now the thud noise sounds like guide rods.

Other items worth considering as noises can travel - motor and transmission and exhaust mounts

My .02

Hi Troy,


It sounds like you have a few issues going on all at once, all of which are common to these cars.

First, your wheel vibration is being caused by one or more of the following things; warped brake rotors, or more likely, a worn idler arm bushing and steering damper.

The popping noises you are hearing when braking are probably the guide rod mounts.

What is happening is you've got a whole bunch of slop in your idler arm. Things go okay until you hit brakes or a bump at which point you get a parasitic oscillation. Basically, your whole steering system is shaking back and forth. This is typical of W126 front ends when you have worn components. At a minimum you are going to need a new idler arm bushing and steering damper, and you may also need some lower ball joints.

Take it to a good suspension shop or MB mechanic and have the whole front end gone over. The state it's in now is NOT SAFE. Also, this condition causes premature wear of the steering gear (not cheap). Get it looked at soon. That vibration can become so bad you'll think you are about to lose control of the car completely. Scary stuff when it gets bad.


-tp

Its really the strangest things because not over a year ago, I rebuilt the whole front suspension and had it aligned by a reputable shop in Tucson. I mean, lower ball joints, control arm bushings (which I guess really didn't need to be done), upper control arms, steering damper, idler arm, tie rods, drag link. Everything's been replaced as far as I can tell.

My only guess is perhaps the idler arm bolt wasn't torqued properly and its wobbling now, which really does scare me.

Either that or the rotors are indeed warped which would explain why it happens at specific speeds and typically with the application of the brakes. The thing is, I've never run down the brake pads, I'm always well ahead of schedule with their replacement. Could they still warp for whatever reason? Also, I think the last guy I took them to left out the shims and just tossed them, could that have done it?

Thanks,

-Troy

a bent wheel will do this, balance perfectly but still vibrate
It needs to be taken of and use a dial meter to see if it runs true
Also, wheel bearings as mentioned, however they would really have to be trashed to have slop, easy to check

Well.. I finally got around to putting in the new bearings... as soon as I got it up off the ground I sort of felt that it wasn't all caused by sloppy bearings although I would say that some observations in handling make me want to replace the bearings anyways.

I replaced the front right bearing. In the process I noticed while I was tightening the lugs that the tire bobs back and forth with tension on the lug nut.

Incredible! The guide rods pop in and out. I immediately went to the other side and checked. The free play was definitely less but still noticeable. Is it possible to crush the guide rod support?

Again, I remember the day the shaking all started. I happened to run into a pretty steep dip in the road which almost makes me think now that it might have been like hitting a curb. Is it physically impossible or could I be on to something? Could it be the rapid popping in and out of the guide rods at certain speeds that's causing the vibrations in the steering?

I think about it and I guess this is probably right because at certain higher speeds this issue becomes hard to achieve. I think that's because there's enough force from the tire assembly coming from the road to hold them into the back-most position.

Let me know what you think,

-Troy

the track rod is simply a "rubber knuckle" of sorts, they get brittle and I guess with the right force they could crush. When they wear you certainly can move them about with a crow bar with the car off the ground

Hmm... I see.

Up to this point, i haven't noticed buckling from the guide rod supports. Only free play within the range it now has to move in its worn out state. It must have been from that particular day when I hit that steep dip. Are they normally that sensitive?

Now that I think about it, I probably didn't absolutely need to replace them although I was replacing everything else and thought... why not?

But could the new ones I put in be cheap or defective somehow? They're Meyle if I recall correctly. What do you think of Febi-Bilstein?

On a separate note. Do you think the job can be done DIY with the springs in? I'm seriously hoping so because I'm quite a ways from my shop in Tucson and every shop out here that does a job involving compressed springs will run you a small fortune.

With the car lifted, do you think its possible that the spring won't exert force in the direction of the guide rod? I think that case would make it possible to just unbolt that L-shape structure and remove the guide rod support.

Thanks again,

-Troy

Be careful
 

It can be done, and have seen it done but I don't recomend it unless you secure the spring with a spring compressor and know what you are doing. The car needs to be on a lift. If the spring gets away from you it can kill you, others may chime in here ,but be very careful around the springs. Also mark the tie rods or else you will need an alignment ( probably will even if you do mark things)

hmm... spring compressor. That's probably out of the scope of my capability...

You know, the thought's crossed my mind. If I had access to one of those oil changing facilities... The kind where you drive over an open pit and the car sits on its own tires and you walk underneath it, then this'd be easy.

I'd just drive the car in, double-chock the wheel of the side to be worked on, and proceed to unbolt the L shaped structure. I think the back plate on the strut rod mount isn't completely accessible when the L shape is completely bolted up, so the L shape would have to come down.

Then the mount could be pushed out and the new one installed. I've considered the whole alignment issue and its probably best to just spray a little bit of spray paint over the guide rod where it meets the mount then disassemble the unit. That way, I could put the new and old mounts side by side and mark off where it needs to be inserted.

Well, first things first, I'll probably just take it to a shop and see how much they'd run me before setting up shop in the parking lot of my apartment complex :\.

-Troy