Is this suspension strut the problem

[Nicebutdim]

2007 E320 cdi. 75k miles

Recently been hearing a patter front O/S when driving on rough road surface.

With the front jacked up and with energetic upward lifting of the front wheel I was able to hear a knock from the upper part of the suspension strut. I thought either top strut mount or worn out shock absorber strut.

I removed the suspect strut today. With the strut removed from the spring I found that If I push the damper rod into the strut body it pushes back as if it were spring loaded so much so that it actually makes a metallic smack sound as it hits the end of its travel when fully extended.

I would have expected the damper rod to be very difficult to extend when compressed and would only return very slowly to its fully extended position.

Can I safely assume this strut is knackered?

 

[BlackC55]

If they are worn they compress very easily or a bit notchy. They will not extend very quickly (if at all).

Remember, suspension knocks do travel along components. We replace, ball joints (upper and lower) thrust arms, roll bar links and shock absorbers for knocking noises. You just have to work out which one is the cause. Sometimes its not easy to define where the noise is coming from. We do more roll bar links than anything at the moment on 211's.

 

[OneForTheRoad]

Horrible set up. Reminds me of super strut on my Toyota gt4.

 

[BlackC55]

Horrible set up. Reminds me of super strut on my Toyota gt4.

Why is is horrible? Its just a traditional Mc strut.

 

[Nicebutdim]

If they are worn they compress very easily or a bit notchy. They will not extend very quickly (if at all).

Remember, suspension knocks do travel along components. We replace, ball joints (upper and lower) thrust arms, roll bar links and shock absorbers for knocking noises. You just have to work out which one is the cause. Sometimes its not easy to define where the noise is coming from. We do more roll bar links than anything at the moment on 211's.

Just to clarify...are you saying they will not extend very quickly if they are worn?

I would expect a good damper to be very hard to extend?

I really appreciate your comments. Thanks.

 

[BlackC55]

What I mean is if you compress it, then let go it should extend by itself in 1-2 seconds.

 

[Nicebutdim]

What I mean is if you compress it, then let go it should extend by itself in 1-2 seconds.

Will that happen in a good damper or a bad one? Sorry for my confusion.

 

[BlackC55]

Will that happen in a good damper or a bad one? Sorry for my confusion.

A good one.

 

[OneForTheRoad]

Why is is horrible? Its just a traditional Mc strut.

Too many links . Arms and balljoints n bushes.

 

[BlackC55]

Too many links . Arms and balljoints n bushes.

That suspension design gives it its ride and comfort levels better than most in its class. Get in a BMW 5 series and compare. Not really much different to your 204 either.

 

[Nicebutdim]

Ok. Thanks

my damper extends quickly enough to make a metallic noise when it hits full extension. That’s just under its own steam. I expect this noise will be much increased when in situ and assisted by the coil spring.

I’m trying to avoid going down the road of throwing parts at the problem as there are plenty of posts on here where people have gone down that road with little success.

 

[BlackC55]

Raise that side up (with everything back together) Get a mate to put a bar under the tyre and pull it up and down firmly. Then put your hand on every joint to feel what is happening. Don't forget the top arm joint too.

 

[Nicebutdim]

Ok. I’ll give it a go. I’ll keep this thread updated as I progress.

 

[Deleted member 151559]

my damper extends quickly enough to make a metallic noise when it hits full extension. That’s just under its own steam. I expect this noise will be much increased when in situ and assisted by the coil spring.

It will never be at full extension on the road with the car weight on it unless you take off over a hump back bridge, you'd have to be trying really hard to get an E class to jump.

 

[grober]

Dampers have essentially two sets of valve-resistance to movement bound and rebound. Their difference often dictates the feel of a cars suspension. In the case of a defective shock one may be more affected than the other. What you were looking at was the shock's rebound characteristic.
this isn't a bad explanation.

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[kid-jensen]

Shocks are pretty reasonable price now.

Go on ebay, search for "Mercedes E320 Shocks" and filter the results by "price + P&P Lowest first".

Then work down the list of results until you reach a make you've heard of.

 

[grober]

AND always replace shocks in pairs especially at the front!

 

[Nicebutdim]

Thanks everyone for the useful comments and explanations.

I thought about the problem last night and decided to have another look at the suspect damper today.

what I found was quite interesting and puzzling. I found that when fully compressed the damper would return to its fully extended position in a smooth and controlled fashion but that the last 2 inch of travel it doubled in speed causing it to strike its stop. I thought this is nothing like anything I’ve seen on the internet (been doing lots of video watching). In the early part of its travel I couldn’t increase the speed of extension by pulling on the damper rod because of the strong damping action. But the last couple of inch I could easily increase the speed. Basically the last two inch of travel has no damping.

To confirm my suspicions I removed the n/s strut and compared the action. It had smooth consistent damping for the full length of travel which is what I would expect.

So I’ve ordered a new pair of dampers. I’ll update when fitted.

thanks all

 

[Nicebutdim]

Just as a little aside. The lower mounting bolts were ridiculously tight on both sides. I had to use a breaker bar extended with a 3 foot scaffold pole to get the moving and they kept up the fight right until the very last threads. Took me the best part of an hour to get the first one off. The rest of the removal was a breeze.

 

[OneForTheRoad]

Just as a little aside. The lower mounting bolts were ridiculously tight on both sides. I had to use a breaker bar extended with a 3 foot scaffold pole to get the moving and they kept up the fight right until the very last threads. Took me the best part of an hour to get the first one off. The rest of the removal was a breeze.

Gas blow torch and wd40 helps. Put copper slip on when you refit to help in future removal.