When to change Shocks/Struts - PeachParts Mercedes-Benz Forum

Bigpete123 · #1 03-01-2006, 01:11 PM

Hello, as my signature indicates, I drive a 1990 300ce (with 190k mi). I have lowered the car, but I was trying to save a few bucks when I did it by delaying my shock replacement.

I have been searching for a good DIY page for this, as I'd like to try it myself. I've never done anything like it before, but it seems relatively straight-forward. I will also purchase a Hayne's book for the w124 to assist me. In my searching, I have yet to find a pictorial step-by-step DIY thread, although some people hinted of one existing on these forums. Can somebody point me in the right direction? I looked at the DIY page and didn't see shock replacement for the 124.

Nearly everybody recommends Bilstein Sports for lowered 124's, so I'm gonna use those. My question is, what does the strut do? Again, I'm far from a mechanic. Google searches have resulted in pictures of units that look much like shocks, but I can't figure out what they do exactly...

And a follow-up question would be, how do I know if they need replacing as well?

So, in sum, here's what I'm asking.

1. Could somebody show me a good DIY page for w124 shock replacement?
2. What do the struts do?
3. How do I know whether my struts also need replacing?

Thanks very much!!

Peter

Bigpete123 · #2 03-01-2006, 06:05 PM

anybody??

#3 03-01-2006, 06:21 PM

The terms 'shocks' and 'struts' are thrown around enough that they're pretty much interchangable at this point. I know somebody will disagree with me, but they do much the same thing. I think of the 'Macphearson Strut' when I think struts, and the plane-jane rear shock absorbers when i hear 'shocks.'

http://www.answers.com/topic/macpherson-strut

Unless i'm mistaken, your w124 has a Macphearson strut up front and plain shocks in the rear. You can replace the rear shocks with little trouble, I think the top nut is in the trunk under the plastic trunk liner and the bottom nut is on the A-arm (duh). Use jack-stands for any suspension job! The new shocks will probably come compressed by some wire, DON'T cut the wire! Take out the old shock by compressing it, get the new one all lined up, THEN cut the wire. And don't ask me why i'm so insistent on this...

I THINK the Macphearson struts should be changed out at a shop beause you will need to be aligned after the job, though I could be wrong. I'm not sure how long shocks/struts last per se, but I'm sure the manufacturer has a mileage recomendation. There is this thing called 'the bounce test' but in my experience shocks are pretty well shot before they fail it, i've heard this is especially the case with biltstein.

I have a pair of sports on the front of mine-very nice. They are 60k old right now and probably ripe for replacement.

If you need a step by step, but a factory CD. I hear they are cheap from benz now..20$?

cheers,
dan r.

Edit: If you're not sure how something works, nothing beats crawling under the car and checking it out...its pretty obvious when you are down there.

t walgamuth · #4 03-01-2006, 07:12 PM

about the bounce test not being reliable for bilsteins. long before they fail that your ride quality will be gone. when it starts to feel bouncy they are worn out. i would look for this on average from 80 to 100k miles.

a strut provides the top part of the suspension assembly and bears half the weight of the car at that corner. the top rides in a large bearing that allows it to turn without twisting the shaft in the strut.

they can be changed at home but the spring requires a spring compressor and using a spring compressor is dangerous business. lots of folks do this at home but i personally dont.

agreed the rear shocks are an easy doityourself job.

tom w

anthonyb · #5 03-02-2006, 01:22 AM

If you're going to do the fronts yourself, you should be sure to find the appropriate spring compressor to keep the springs from letting loose. As far as I know, there are only one or two brands that will work on the car, none of the other brands are robust enough to safely secure the springs.

A good way to test the shocks is to find a wavy road, or one with some dips in it, and drive over it at moderate speed. If either end oscillates up and down much, it's probably time to replace them. I think the W124 shocks last a good long time, 200-250k miles, so it may be time to replace yours.

Duke2.6 · #6 03-02-2006, 02:33 AM

The fronts are not true MacPherson struts because the spring is NOT concentric with the stuts. They are usually referred to as "modified" MacPherson struts.

The struts can be easily changed with the front control arms resting on jackstands so vehicle weight keeps the spring compressed - two bolts on the knuckle and the shaft nut up top. A spring compressor is not neceassry. Alignment should not be necessary after replacement. Always remove the top mounts and carefully inspect them for cracks. Replace if necessary.

High pressure deCarbon struts/shocks can last nearly forever, but some fail early. Failure is usually indicated by a major loss of oil.

If body rebound control is adequate and there is no evidence of oil loss, the OE struts/shocks don't need to be replaced.

Duke

t walgamuth · #7 03-02-2006, 08:29 AM

thanks for the detailed explanation about the modified struts. i have often wondered about that and speculated that they may be easier than the true struts.

tom w