The brief
The C180 was vibrating heavily at idle and through acceleration, the owner heard a clunk every time the gear lever moved between Drive and Reverse, and the engine was visibly rocking in the bay under load. Three signs of tired mounts.
The mounts are the rubber-and-fluid blocks that hold the engine and gearbox steady and soak up their movement. There are a few of them, supporting the engine, the gearbox, and a lower support that stops the whole assembly from rocking. When they sag and split, the drivetrain shifts around: the clunk on take-up, the buzz at idle, and the visible rocking under throttle.
The diagnosis
On the lift the front engine mount was found torn, with its hydraulic fluid leaked out, and the rest were no better, the rubber collapsed and deflecting well past spec on each one.
Replacing one side and leaving the others would have left the drivetrain isolated unevenly and meant a return visit soon, so the right scope was the full set, every mount holding the engine and gearbox, renewed in one go.
The work
The engine and gearbox were supported, then each failed mount removed in turn and a new Mercedes-spec replacement fitted in its place, every fastener torqued to spec in the correct order.
With the new mounts in, the engine was run at idle and then under throttle to confirm the vibration was gone and the drivetrain sat where it should before the car went back to the owner.
The outcome
Smooth idle, no rocking in the bay under acceleration, and no clunk on Drive-Reverse shifts.
The C180 went home with the drivetrain isolated again. For the owner that is a car that feels solid and refined rather than shaky and loose, and doing the whole set at once means all the mounts age together from here, instead of a string of return visits as each old one gives out.
