They're worn from age, not mileage. When the car is sitting, the engine rests on the mounts. Cars really do age with time, and often it's harder on them than mileage. The new mounts are pretty much like the old ones (my 98 C230 got new mounts this year too) and will probably last another 8-9 years...

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John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

HI Iacombe

I don't have a clue what they are talking about with the alignment issue. However once the mounts are replaced you need to readapt the "Sensor Gear Adaptation." If this isn't done chances are good you will get a Check Engine light and have misfire codes. You will need a scanner that has this function in it to re-set the adaptation.

This job has very tight working quarters and will require a few busted knuckles. My WIS shows 2.4 hours to replace both motor and transmission mounts. Good luck.

fasthair

Is it just me, or does this just not sound right??

So, 2.4 hours for all three mounts plus the "readapt"? Not bad..

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2000 c280 Sport (looks like an upgrade, feels like a downgrade)
1991 190e 2.3 (sold)

I read somewhere that disconnecting the battery would reset the on-board computer. Would this work instead of a Sensor Gear Adaptation?

Irieite… weather is sounds right or not this is just the way it is done. I’ve been fixing MBZ for almost 25 years and go to update classes yearly. I learn something new every time and this was one of the things I learned at one of them. In fact this must be done when you replace the crank sensor, motor mounts, flywheel, ME controller and in some cases to cure misfires.

Iacombe… disconnecting the battery cables will not re-set the Sensor Gear Adaptation. It must be done with a scanner then a certain drive cycle must be done to perform adaptation. Drive the car in 3rd gear at 2,100RPM with 50% load on the motor. Now you can see why you need a scanner to do this. The only way to tell if you have 50% load is with the scanner.

fasthair

Still doesn't make sense on the motor mount swap.. Do any cables to the trans need to be removed in order to swap out the trans mount? Maybe i can see why in that case... But just for the motor mounts?

Can anyone else confirm or deny this??

At 6 years and 67k on mine, I'm probably going to have to replace the fluid filled motor mounts on my c280 as well. I did it on my 190e 2.3 and it was a piece of cake. But of course, no electronically controlled tranny there..

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2000 c280 Sport (looks like an upgrade, feels like a downgrade)
1991 190e 2.3 (sold)

First you must understand how the system works to detect misfires. I’ll see I can get this right. The Motor Electronics (ME) computer uses the L5 (crank) sensor for a few things one of which is telling the ME how fast the engine is running. The ME can see the slightest variation in crankshaft speed. As a cylinder fires it speeds the crank up a given amount and the engine itself moves because of this. When a weak cylinder fires the crankshaft doesn’t speed up as much and the ME flags the misfire and shuts the injector off on that cylinder to protect the cats from damage. Now with flat motor mounts the engine doesn’t rock or move as much as it will with good mounts. When the engine doesn’t move from flat mounts the crank actually spins faster because the inertia isn’t lost in the mounts flexing. With new mounts the ME will see slower crank speeds because now some of the inertia is lost as the mounts flex.

Does this make sense and clear up why the adaptation must be done?

fasthair