124 rear fails bounce test
 

when the rear is 'bounced' at each corner it continues bouncing slightly a couple times more. the front bounces then returns to normal position straightaway. I presume this means worn-out shocks? rear of the car feels kinda squirelly at highway speeds too and i have the 60mph steering wheel vibration problem too... oh what fun!

Yes, your shocks are badly worn.

"Bounce tests" don't mean much. The true test is if the body wallows around excessively on bumpy or wavy roads at moderate speeds.

The OE deCarbon type shocks/struts generally maintain their damping characteristics for a very long time, then fail completely, which is usually evidenced by significant oil leakage.

Duke

thanks for your replies.

i don't see a whole lot of oil leakage though it looks like there is some on there. These look like the original struts so ast 193K i'm figuring time to replace?

Bilstein, here I come. ;)

that's what i was thinking:-) question is, do I go for comfort or HD???

Depends on the ride you want. Comforts will give a very smooth ride at the expense of a bit more body lean. HD will ride considerably harder.

I put HD on the Volvo, and wish I'd stuck with the comforts, it's too harsh on the highway now.

Check the condition of the rubber bushings on the links on the rear suspension while you are in there, too -- any evidence of shredding on the inside end of the torque strut (upper diagonal from wheel carrier to subframe) means you need new ones. Do both sides if one is bad, I didn't and now need to do the other one. When this link goes bad, the toe on the rear wheel changes with torque, so that the rear end moves on acceleration and deceleration. Makes it hard to drive.

If you just have vague and wandering steering, get an alignment done up front using a spreader bar. If the guy at the alignment place looks blank when you say "spreader bar", take it someplace else, as setting the front toe without the spreader causes incorrect toe-in (too much) and the car will feel like an elephant on rollerskates.

Peter

Peter

I have heard that rears don't last as long as fronts. If you stuck with comforts you start by replacing just the rears and see what effect it has. The rears also cost about half of the fronts and are easier to put on.

PSFRED and spreader bar
 

Ok Fred, Give us more info on the spreader bar, what it does, and why it is critical. I just put new wheels and tires on a W210 and want to get it checked just in case. (plus it may be pulling just a hair to the right since I replaced the brake rotors in the front and had to wail on the right rotor pretty hard with a 5 pound beater to get it off. Yeah I know I should have used a puller, but it was at my other garage at the time) Also, will incorrect toe cause reaction to crowns in the road?

I think i'll go with the comforts, although I like a controlled ride, from the postings it seems the HD's are a little too hard (especially with the roads 'round here, and I like to run pretty high PSI's)
I was poking around the other day to look for fluid leakage and the rear bushings seem to be in pretty good condition all-round. Not amazing, but i think ok for now.
The front sway bar bushings I want to replace though as they are starting to crack- does anyone know if i need 1 or 2 of these kits for the front?

one more thing...
 

does anyone know where the chassis # is on the W124, or what chassis# a late 91 300e is?

91 300E will be a W124. It's in the VIN number, starts out WDB124, I think.

You have all the bits for the sway bar there -- four rubber pieces and the bolts and nuts. Only four rubber parts for the W124.

The spreader bar is a bar used to spread the front wheels at the front side when setting the toe to take all the play out of the suspension. McPherson strut systems tend flex a bit under load, and if that flex isn't provided when aligning, the toe won't be correct. Yes, improper toe will cause the car to be excessively sensitive to crown and to follow ridges or ruts. My 300D needs the front done, but I'd not going to align it until I get the other links replace in the back. I had the TE done this summer when I put new tires on it, and it is almost impervious to crosswinds or crowns. Quite a difference.

Peter

re the sway bar- i should have worded my question better- what i meant was do i need one of these kits for each side, or does the kit do both L & R bars?

One sway bar, a bushing on each end and two on the frame. You have the entire set of bits for the car, both sides.

The older swaybar setups had four bushings on each control arm, and two large bushings on the frame. On the W124, there is a circular bushing on the control arms and two circular bushings on the frame.

Be careful not to twist off the bolts welded to the control arms.

Peter

Shock absorbers have NO effect on steady state body roll. Shocks are purely transient damping devices that provide a resisting force proportional the the velocity at which they are stroked. They can effect the rate at which the body rolls when you pitch into a corner, but not the steady state roll through a sweeper.

The Bilstein comfort shocks should be calibrated equal or near equal to OE. Mercedes probably has the best ride/handling compromise for normal street and highway driving of any sedan built, and I would not install the HD Bilsteins unless you're doing some serious racing or rallying.

Duke

I know that excessive, or severe suspension bouncing can be dangerous, but I like the ride better of a softly sprung car like this. Seems like in the past- I kept buying cars that had just had the struts replaced, that gave the car a harsh ride. If you do replace the struts- go with original OEM (Mercedes) struts. Aftermarket struts tend to give a car a very harsh, firm ride. Just my opinion.

It is good to see the recommendation of the use of a speader bar during alignments.

I forgot, does the bar go in between the front wheels at the front or back of the front axel line?

Haasman

Front, either at the centerline or 45 degrees down, I think. Don't remember the exact instructions in the CD. Don't do alignments myself, beyond measuring tie rods when I replace them and setting them to the same length as the old one, or "seat of the pants" ones to get the car down to the shop.

Peter

Thanks Peter,

So the wheels want to be spread apart at the front as one drives down the road, thus the spreader bar simulates that during an alignment?

Haasman

chazola

Be sure and check the upper shock mounts as well. If you see little tiny cracks from the top, there is a good propability they are torn at the bottom.

Haasman

well, I ordered some Bilstein Comforts, front sway bar bushings and should hopefully have them installed this week.
My front lower control arm bushings are looking really worse for wear (rubber is all cracked) so they'll have to get replaced too- I presume that's a pro-shop job from the look of things. Anyone know how long the labour should be on those? Maybe i should do balljoints too while they're at it...

Hopefully the new shocks and bushings will help restore the handling.

Then I'll only have to replace the front cover (leaking), replace the leaking rear main seal, replace the motor mounts, fix the driver's side dash speaker, cure the harsh-shifting transmission, fit euro headlights and i'll be good to go.
remind me, why did i buy an old mercedes again?!:-)

chazola

Replace the rear sway bar bushings (very little cost) as well as check the links connecting to it.

You may not need ball joints. Surprisingly, they seem to last a long time (depending) on the 124 cars.

Haasman

haasman-

when i was checking the rear suspension the sway bar bushings looked in ok condition, though I'm not sure if that's a good indication if they're worn or not. The car does have a slight 'back end doing it's own thing' feel on the highway.

I noticed that the link that connects to the sway bar at an angle
(not sure what it's called, should have taken a pic while i was under there) did have some movement where the two bars connect, i.e. I could pull on it and move it back and forth somewhat.

chazola

In my experience, the rear sway bar bushings rarely look worn, but once you take the old ones out and compare to fresh ones, it is very obvious the difference.

The links should only pivot but not allow for any movement. Have you checked your upper diagonal suspension links. These are often the ones to wear out quickly and will give a wiggly feeling from the rear of the car.

Haasman

>Have you checked your upper diagonal suspension links.

are these shorter than the main (thrust arm etc) links? excuse my ignorance, atill learning here! just trying to figure out if we're talking about the same part.

The link i noticed had movement in it comes straight up from the wheel carrier, then connects to another link at an angle.

The particular one I am speaking of is under the group 75 in this picture. This happends to be of a left rear suspension.

Haasman

ok... not the same one i meant. I'm probably on about the sway bar I think.
All the other links were solid.
I think i'll do as you suggested and replace the bushings. that with the new shocks and we'll see if i still have the problems.

Haasman:

The dynamics of the front end on the W124 appears to apply some pressure outward on the front of the tires. This may be true of any car, but at least on MBs, this requires the spreader bar to get correct alignment while running. Believe me, it makes a difference! The TE is almost completely oblivious to crosswinds -- the only thing you feel or hear is the wind roaring across the sunroof! The 300D wanders all over the place, but I have to replace the left side torque link and thrust linkd, so I will wait until then to do a 4-wheel alignment.

Peter

Spreader bar
 

Peter

Yes I agree. So many alignment shops don't use this bar. I finally had to go to a dealer to get the right alignment (with the bar).

I have found generally that alignments done without the bar use tend to result in the outside edges of the front tires wearing early, not to mention the twitchy handling you described.

Haasman

Improper toe -- too far out or too far in I don't remember. Too much toe-out will cause the car to wander terribly, follow directional pavement, and climb the crown on the road, as I remember.

Peter

Also check the front dust boots (plastic bellows). These usually disintegrate long before the shocks go. I replaced them on my 190 last year. They are not expensive parts at the dealer. Since the struts have to come off to replace them (not at all a hard job) I also removed and carefully inspected the top mounts and they appeared as new - no cracks.

Duke

here's how my strut mounts look- (driver's side shown) some hairline cracks in the rubber... no clunks or creaks (yet)

chazola

If they are cracked, replace them.

The cracks at the top are not the most important place to look. When you have them out, turn the shock mount over and look underneath. Mine (on the 190) had very similiar little cracks, but underneath were torn considerably creating and awful lumpa bumpa lumpa sound when I went over bumps.

Haasman

mine aren't making the umpa lumpa bumpa sound yet... but i'm sure it's onloy a matter of time...

new rear shocks and front sway bar bushings just arrived, so hopefully they'll get fitted tomorrow depending on the weather (bloody freezing here, wish i had me own garage:-)

It is a bummer when you get your new parts but it is really just too cold to put them on!

With sway bar bushings, be sure the car is on the ground and level before you tighten the bushing cap holders. This way you avoid any preloads.

I would say the same holds true for the rear shocker's lower bolts.

If you are going to wait on the front shock mounts, they are not too hard to replace separately. You simply leave the front wheel on, unbolt the three mount bolts and the center shock nut, jack up the car enough to compress the shock and get the mount off.

Installation is just the reverse with the added pain of collapsing the shock enough to get the shock mount on top of it before it wants to extend.

Haasman

W124 no longer fails bounce test :-)
 

got my bilsteins on-yay! my first major car repair ever done. I'd say the hardest bit was getting the old nuts off- they really didn't want to budge.
The old shocks were really shot. Funnily, seemed to scrape and generally injure myself more installing the second one- hmm... maybe 'cause i was getting hungry.
Anyway, car feels much happier now and although i car hear and feel every little bump in the road, I like it that way:-)

Haasman-

here's a photo of the link that has some movement in it- sway bar to the link the connects to the lower control arm. Bushings don't look too bad condition but i can move the link back and forth a small amount.

New shocks .... nice .... new Bilsteins, really nice!

It is hard to describe exactly, but the idea of the sway link to the sway bar end is to allow movement (up and down of the link connected to the each wheel) but not any excess play.

A tight connection is very important. Even a tiny bit loose connection translates into excessive body roll, often hard to perceive.

That is why the sway bar bushing replacements make such a difference. Yes the old ones hold the bar, but just the tiniest bit of play translates into sloppy handling. It is especially perceived during hard and fast lane change transitions; the car with fresh bushings and good links just feels tighter.

Haasman

guess i'll be ordering my new rear sway bushings and links then... at least they're cheap:-)

Need to get the subframe mount bushings replaced too- all cracked.

that one's probably a bit out of my league though- I'll take it to the shop for those.

couldn't have asked for a better day today- 45 degrees, sun all day and no wind. Good thing my mum sent me this tartan rug from the UK.... very useful.

Spoken like a true DIYer!

(We won't tell her about the rug)

Enjoy the fruits of your labor.

Haasman

How far down did you run the nuts on the top of the shock? They should only be as far down as it takes to get a thread or two showing on the top nut, or the equivalvent distance if you have only an nylock locker nut. If you run them down til they are "tight" the cars gonna ride really hard, the rubber will be completely compressed and cannot absorb any roughtness. If too tight, just run them back up.

I did this on the 220D, rides way too hard, but didn't fix it -- I'll replace the cheapo Gabriels with Bilsteins if I can save it.

Peter

hmmmmm...
 

i did do them pretty tight- i'll check again tomorrow and see just how much.
thanks for the info.

actually...
 

I just remembered- the new shocks came with 1 nut- is that the 'nylock' type one? The original struts had 2 nuts, and I re-used those as i could only get the one that came with the bilsteins threaded down a certain amount- is this how the nut is supposed to work? I though there was something wrong with it so i used the originals, but maybe the new nut works in the way you're suggesting so it doesn't compress the rubber too much?

Regardless of which nut or nut combo you used, the idea is to not tighten the rubber under the large washer too much.

Personally, I've always cranked them down. I rather loose a little compliance for the firmer ride and road feel.

Haasman

I like a firm ride too but I'm wondering if i tightened too much- it's pretty solid when you try the bounce test now -it's very stiff to push down a little way and it returns to the level position very sharply. I guess this is probably normal behavior for a brand new strut though.

My Haynes manual gives torque settings for the nuts so i'll go get a 17mm ext. socket so i can use my torque wrench to set them- 'cause i'm kinda pedantic like that :-)

The nylock nut will be very hard to turn after it goes past the end of the thread. It's supposed to, it "locks" on the thread so the nut won't unscrew. Quite a pain when you have to unscrew one off a rusty bolt about half and inch, it won't spin freely until the nut is almost off.

Your new shocks will be somewhat stiffer than the old ones for a while, they will get a bit softer with some milage. Not as squashy as the old ones, though! How does it drive now?

Top nut should only be down far enough to two threads to show on the shaft, then lock the two nuts together. Nylock nut should be less than 1/4" down, or in the position the bottom nut would be.

Setting the nut correctly don't change the handling significantly, it just allows the rubber to absorb the initial roughness and smooths things out. That way you don't feel gravel and rough pavement through the seat.

Peter

That is how my 1990 Lexus LS400 was before I installed OEM Toyota/Lexus struts on the rear. About 6 months ago- the previous (an original) owner had "KYB" high performance struts installed. I could feel the rear suspension picking up every bump and the rear was difficult to press down. I actually like a soft ride and I knew this was not how the LS400 was supposed to be. I remember riding in my aunts 90 LS400, and it has a "floaty" ride, but I am guessing her shocks are getting worn. I have seen several LS400s, with floaty, super soft suspension. They are supposed to be somewhat soft and floaty on the LS400. I had the KYBs removed and had the Toyota struts installed in order to get the ride like the car had when it was new. The car has a much softer ride now. The suspension takes the large bumps with ease and you can hardly even feel them. I am really pleased now with my suspension.
I was very impressed with soft ride that the 84 300SD I test drove a few weeks ago. It was very soft and soaked up all bumps, but I am assuming the struts are a little worn.

Sounds like you saved a little money doing the change yourself. Did the rear seat have to be removed? I know that on most Toyotas (probably most Japanese cars), that the rear seats and sometimes rear package shelves have to be removed in order to change the rear struts. I had to pay $90.00 to get mine changed.

I've been told that KYB shocks are very stiff. Some folk like them, we will see since I got a set for the front of the 280 SE for cheap on eBay. If I don't like them, the originals go back in.

I also bought a set of used shocks for the rear. Unless they are completely gone, the will be better than the Monroe Gasmatics (or whatever) that are back there. Too much gas pressure (the rear sits up too high) and so stiff you'd think they were solid.

Peter

I prefer the stiffer ride as i like to drive fairly aggressively and 'throw my cars around' a bit (within reason!:-) I know for this i should probably be driving a VW golf and not a Merc, but I'm not a 'boy-racer' as we say back in the UK.
I do like my cars to have good solid handling and my old Peugeot had good suspension (for French farm roads i'm told) so i'm used to the firm feel.

Rear seats didn't have to come out, thankfully, just the trunk liner on each side needed to be pulled back. Not a difficult job- took me 4 hours as it was my first time ever and the bloody nuts were being stubborn coming off.

The car doesn't wallow like a big whale going over hilly country roads now:-)

Subframe Mounts
 

There was a mention a number of posts in this thread back about not being able to do the subframe mounts. You might want to do a search, read some of the threads and decide if you can or can't. If I recall correctly, there are ways for a DIYer to do that job, given fabrication of some special tools, care with certain phases of the job, and time and patience. If you enjoy doing your own work, check it out before you make a decision. Just make sure you make an informed and careful decision.

Here is a good one by Cornblatt:

http://www.peachparts.com/shopforum/showthread.php?threadid=76569#post485053

Haasman