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

Well, what you said about inertia on new vs. old mounts makes sense, but if the ME can "adapt" on its own as the mounts deteriorate, why can't it do the same with new mounts? And, what about the shift adaptation issue that you mentioned earlier? I still don't get how that gets screwed up by the motor mount change..

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

Yes it does adapt as the mounts settle over time. When you install new mounts this is a drastic change and the ME must be ‘told’ that this happen and to learn the new information. The ME is very sensitive to RPM change giving it the ability to detect misfire. The ME can detect a misfire that you can’t even feel.

I can make an ME system learn a motor running on 5 cylinders as running ok. Then when I make it run on 6 cylinders it will see this as bad running engine and flag a misfire code. Again this is a drastic change.

I never said anything about shift adaptation. Sensor Gear Adaptation is what I am talking about. Sensor Gear is MB speak for flywheel. Like I said earlier anytime you change one of the components I listed this is a drastic change so the ME must be told that it happen and to learn the new information.

fasthair

Thanks for the info and sorry about my misinterpretation about "gear adaptation".

What you've said makes sense. But, having said that, when the time comes, I'll take my chances and change the mounts myself. If it triggers the CE light, then I'll take it to the dealer or MB indy, tell them what I did and let them "readapt" it.

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

First, thanks for the information on this post. I used it to test the motor mount causing vibrating engine by jacking up the engine. Sure enough, the vibrations went away. So I bought two engine mounts and one trans mount for $217 from thepartsbin.com and got to work. The book time is 2.5 hours for this job. The dealer wanted $475 parts/labor ($125 per mount). So I figured with my limited tools, working in my garage in 90 degree heat, I could get er done in 5. Disclaimer, I used to work as a mechanic for Chevrolet and Toyota. I now drive a desk as a computer analyst. Anyway, you will need Torx type sockets, E10, E12, E14 to complete the task. This is to make room to remove the huge mounts by removing the Alternator and the A/C compressor.

Don't be intimidated by the tight space, once you remove the easy to get to lower bolts on the mounts, you can jack up the engine to make room. Do one mount at a time. I did the easy trans mount in quick order. Then I tackled the drivers side mount. I figured that was the most fatigued due to engine torque. If it was a ***** and I only got one done, this would be the one to do. The top bolt is a little tighter and harder to get. I had to use a 5/8 open end wrench. It may be 16 mm, but I did not have one. It was not that tight and came out after minutes of turning the bolt by hand. Trick, you can spin the mount to lossen the bolt too. Once the bolts were out, I slipped the mount out by moving the A/C out of the way. The new mount went in and I was careful to line it up with the tabs on the frame so it angled towards the motor. When starting the bolts, make sure to start the top one firsrt since it is so tight.

I compared the old mount with the new. The old mount was 1/2 inch shorter due to fatigue. No wonder it was causing a vibration! I knew then that I had to do the other side as well.

I had it half done! Only the passenger side to go. It went about the same as the driver's side. The alternator was a ***** to line up with the brackets, I about passed out from the heat wrestling the bolts in. Once it was back on, it was smooth sailing.

Bottom line,
I got the job done in 4 hours and only lost 4 pounds. I took the car for a spin and was very pleased to find it as smooth as a baby's butt. No need to recalibrate any sensors.

Thanks guys for the help giving me the courage to tackle this job and save $250!
John Rolstead