I have replaced the upper strut mounts over the weekend. Two days later I checked and the new mounts have already severe cracks in the rubber, actually worse than the old once. The strut mounts were purchased from MB. There was no jaming, forcing or bending of anything when I installed them. The crack in the rubber on the left side strut mount is a horizontal crack almost 2" long in the direction of the car, engine side, and the distance between the upper portion and lower portion of the rubber is almost 1/16" I took a small kitchen knife and I could push the blade into the crack.
Has anybody experience that or does anybody know why this happened.

Thank you all in advance.

is the rubber actually cracked, or the coating on the rubber? they have a thin coating on them that will crack, giving them the illusion of being cracked,

I second that.

They shouldnt crack in any form. I replaced my struts myself, and have not noticed any cracks. Are you sure your springs aren't weak? Or even your shocks.

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190e 2.6 1990. 300,000 KM
C230 K 2000, 130,000 KM

Before I replaced the strut mounts I jacked up the car and checked for free play by moving the wheel at the 12/6 o'clock position and other positions. I couldnt feel any free play. The height of the car at the front is correct. The car doesnt bounce driving over bumps etc. The shocks are not leaking. There was no coating on the strut mounts. The crack described in the original thread looks like a deep gash 2" long. I have to find out why they cracked after two day before I replace them again.
I have serviced and maintained this car for nearly 19 years. It has 360k on the odometer. Engine runs perfect. Always used Mobil Oil since day one of ownership. No vibration at any speed.
The only complaint I have about this car is the oil leak at the bottom of the chain cover. That has been fixed twice since I owned the car, and its due again. This seems to be a chronic problem on this engine.

Thanks again for the help.

That sucks, ask your MB dealer why the mounts could have possibly cracked?

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190e 2.6 1990. 300,000 KM
C230 K 2000, 130,000 KM

I went to my trusty independent repair shop and he told me the same thing, they shouldnt crack. He looked at them really crafully and we noticed that some rubber is actually flaking off. He said this is really old old stock. I will take them back, they will have to replace them.

Thanks again for everything