Quick w202 question
 

Ok, so I was at the dealer the other day and spotted a beautful 1998 c280 sport in immactulate condition. I fell in love with the car immediately. The car runs great and pulls strong, but I have just one question.

When I first test drove the car, the car would vibrate pretty harsly at idle in Drive. Now I was able to keep the car on an overnight test drive, and noticed that after the car thoroughly warmed up, the vibrations dissapeared. At first I thought i was motor mounts, but if the car had bad motor mounts, would the harsh vibrations dissapear after the car was warm?

Just wondering as I am in love with this car but am hesitant to put a deposit down on it due to the rough idle.

Anything helps.

Thanks in advance.

No, the vibration would still be there!

The V-6 M112 engines have gone thru 4 different part numbers for motor mounts since 1998! The latest numbers are a highly modified version & seem to last much better.

Any time you consider an early M112 powered car have it checked for modified crank damper & for service history!! PRE-purchase inspection!!!

So I took the car to get a PPI, and everything checked out. However, they DID say the crank pulley had an "early" part number. So i took this into account. I drove the car back to the dealership and they had one of their guys look at it. He couldnt see the part number from outside the engine, but told me since the car had gone 84,000 miles without a failure, it either has to be a newer pulley or one that just hasn't or won't fail. The dealer technician said not to worry about it, and that it was turning very straight with no play. Should I worry about this issue?

The dealer's tech is BS'ing you. Balancer failures happen at all kinds of mileages, and if you have an early version or if it looks at all like it's coming apart, it MUST be replaced. If not, it can come apart and do THOUSANDS of dollars of damage in the engine bay.

What did the PPI reveal about the shaking? I would not buy the car with that behaviour, or the old balancer. Known failures on the M112 include the balancer (many newer part #'s) and crank position sensors. Also, be careful about service records, since 98 M112's were shipped with dino oil and have the dreaded sludge problem if the FSS is followed AND the engine is not switched to synthetic. While MBUSA has extended the engine warranty to 150K-miles, I wonder how difficult it is to get coverage. You must prove that it's sludging AND you at least changed the oil as per the FSS. Also, I'm not sure if the warranty transfers to new owners.

Since their technician said "all's well", they should have absolutly no problem warranting the part & related items. Such warranty, of course should be in writing and form part of the purchase contract. They may choose to replace the part to make the deal instead of giving a warranty.

Ok, so i'm going to change that pulley as soon as possible. But does anyone have any idea why the vibration would occur like I posted in my first post?

It will be cheaper if you get them to replace it as part of negotiating the deal.