I have a '99 C280 with 201,000 miles and have noticed recently that the motor vibration has become more significant. While not broken, can motor mounts "harden" and in effect, transfer vibration and noise to the chassis and the passenger compartment?

Yes.

__________________
I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

Dave,

How many are there and are they difficult to replace DIY?

Brad

Motor mounts typically collapse over time. The rubber "sandwich" tears or collapse, allowing motor vibrations to transmit to the frame. Usually, there are two motor mounts. You may also want to inspect the transmission mount for the same condition.

__________________
1995 S600, 1 of 618 (sold)

"Speed is just a question of money...how fast you wanna go?"

LONG LIVE THE W140!
Visit my Web Page at www.v12uberalles.com

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1W70PZW4N2140JLB0S&year=1999&make=MB&model=C-280-002&category=A&part=Engine+Mount

There are two mounts. I dont have any experience on your models car so I cannot say how difficult it will be to get at them. I have always had to use tools that are optimized for hard to get at spaces to get the bolts out. Typically they are not the easiest things to replace.

__________________
I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k

i dont know about benzes, but i know motor mounts are something i never want to do again and i would have an indy do them anyday.

__________________
1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

You have two gel filled mounts. They split and leak out the glycol gel, and the engine shakes.

Replacement is fairly easy if you can get to them. I'm not familiar with that model, but there is most likely a bolt top and bottom, the mount itself is a fairly large metal and rubber item about the size of a softball.

To replace them, you have to jack up the engine a few inches and remove the upper and lower bolts. Top is likely a 19mm hex head, the bottom is likely an 8mm cap screw (Allen head). Lift engine until you can get the mount out, then jack another inch or so so the new one will fit in (maybe more!). They are indexed with a pair of ridges on top and only fit one way, make sure they are in correctly, then tighten the bolts. Watch that you don't drop the bottom screw into the frame, it's a bear to get out.

Best to use an engine hoist and the lift eyes or a floor jack on the oil pan with a board between to lift the engine.

The main difficulty is reaching the top bolt on some models. V8 engines and turbodiesels really cannot be reached from the top.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

BPH - take a look at this thread on mounts:

BPH- I replaced the motor mounts on my 90'420 SEL 171,000 just last month and they were as flat as pancakes, after they were replaced the engine rose an inch! Before hand the car would vibrate so much in park I felt like a milkshake! No vibration what so ever now. There are three- two for the engine and one for the transmission.

__________________
"It's normal for these things to empty your wallet and break your heart in the process."
2012 SLK 350
1987 420 SEL