Original 1981 MB Engine Shock - How to Test?

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JHZR2

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I am doing engine mounts on my 81 240D. I have to remove the engine shock to lift the engine, in order to do mounts.

The car is very clean, the shock looks like it is in good shape. How do I know if it is good?

If I push the shaft all the way in, should it extend back out?



Likewise, if I pull the shaft all the way out, should it pull back in?




When I push it, should I feel any change in how resistive it is? Should I hear anything? Along the travel, I feel two spots where it gets easier for a fraction of a mm, then keeps up the resistance. When moving it along the full length of travel, I hear what Id call a fluid sound, like there is some oil in there moving between chambers.

Any recommendations on how to test?

Thanks!
 
Maybe so, that would be (Id guess) where the engine typically sat height-wise? But whats to say its actually worn? Any excursion beyond that spot and its stiff/resistive.
 
I would guess it is a damper so is there equal resistance in both directions or oil leaking from it?
 
It's almost certainly fine. These are only there to avoid severe engine rocking when rotational inertias make it want to rotate clockwise upon application of Wide Open Throttle (WOT) conditions.

It is a very simple device, unlikely to wear out in my opinion. But to test, reinstall, and have someone activate the throttle (idle > WOT > idle) while you observe the engine rock while the hood is open. It's somewhat difficult to describe what to expect, but in your case you could observe without and with it in place. It just moderates the movement, not eliminate it, but in some cases with no damper the intake can hit the hood if closed.

Many engines do without it, or only install it on high performance variants. It's a good thing to have but as long as no part of the engine hits the hood or other parts in the engine bay, it's not really even absolutely necessary in most cases. I like to have one, though, and install one in vehicles that lack one from the factory.
 
All indicators say its fine, these are not gas charged so there is no pressure or vacuum just a simple oil chamber and valve.
It is only a simple oil damper with a very short travel and is really only in operation a idle and near idle speeds, at higher rpm the oscillations are minimal.

The fact it has oil in it and from the picture isn't leaking is a good sigh its good. The question in my mind is with any part this age is do you reinstall a 40 wear item?
The fact you have moved it probably more than it ever did in regular service could have stressed the ancient seals inside, or not?
 
Originally Posted By: Trav
All indicators say its fine, these are not gas charged so there is no pressure or vacuum just a simple oil chamber and valve.
It is only a simple oil damper with a very short travel and is really only in operation a idle and near idle speeds, at higher rpm the oscillations are minimal.

The fact it has oil in it and from the picture isn't leaking is a good sigh its good. The question in my mind is with any part this age is do you reinstall a 40 wear item?
The fact you have moved it probably more than it ever did in regular service could have stressed the ancient seals inside, or not?


The fact that it's 40yo is part of the consideration. The mount and rubber parts are not cracked, and actually are soft and compliant. I'm planning to reuse them. Replacement of this mount is easy enough. It's really just three 10mm fasteners.

My car is smooth as glass at fast idle and driving, but has a nasty vibration at slow idle. I want to rectify that as much as possible. Not sure how much this helps with the mitigation...
 
They help but not as much as you would thing, that 4 cyl diesel really wants to hop around at low idle. Just reuse them, as long as there is some resistance if you try to push it fast and you hear the oil moving its okay.
 
Originally Posted By: JHZR2
Maybe so, that would be (Id guess) where the engine typically sat height-wise? But whats to say its actually worn? Any excursion beyond that spot and its stiff/resistive.


That piece is 37 years old, even if good it must be on its last legs, why not replace it while you have it out?
 
Last edited:
Originally Posted By: Pelican
Originally Posted By: JHZR2
Maybe so, that would be (Id guess) where the engine typically sat height-wise? But whats to say its actually worn? Any excursion beyond that spot and its stiff/resistive.


That piece is 37 years old, even if good it must be on its last legs, why not replace it while you have it out?


No reason really, other than that the original one is still stiff, and replacement is maybe a 20 minute job.

At the same time, the German-made part is only around $28.
 
Originally Posted By: Pelican
Originally Posted By: JHZR2
Maybe so, that would be (Id guess) where the engine typically sat height-wise? But whats to say its actually worn? Any excursion beyond that spot and its stiff/resistive.


That piece is 37 years old, even if good it must be on its last legs, why not replace it while you have it out?


The new one will not be made in West Germany.
All original, baby down to the grease in the front wheel bearings.
 
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