MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
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In this guide (5 sections)
Are you wondering whether your Mercedes-Benz has bad engine mounts? Here is a simple way to check whether the engine mounts are worn or damaged. A common symptom of a worn engine mount is excessive cabin vibration while the vehicle is stopped in Drive.
Before You Start
This procedure requires a helper. Never stand in front of or behind the vehicle while the engine is under load. Perform this test outdoors on level ground with clear space around the vehicle. Apply the parking brake and place wheel chocks behind the tires. Keep everyone away from the front and rear of the vehicle. The observer must stand beside the vehicle and keep hands, clothing, and tools away from moving engine components.
How to Test the Engine Mounts
- Have your helper sit in the driver’s seat and start the engine.
- Have the helper press and hold the brake pedal firmly.
- Shift into Drive and briefly apply light throttle while holding the brake pedal firmly. Watch the engine from the side of the car.
- Return the engine to idle, shift into Reverse, and repeat the test briefly.
- Return to idle and shift into Park.
Did the engine lift or rock excessively, as shown in the video?
What the Result Means
A small amount of movement is normal. A mount may be damaged if the engine lifts sharply, rocks excessively, makes a clunking noise, or contacts nearby components. With the engine off and cool, inspect the mounts for collapsed rubber, torn sections, excessive sagging, or fluid leaking from a hydraulic mount. Also inspect the transmission mount because it can cause similar vibration and movement. Cabin vibration alone does not confirm a failed engine mount. Rough engine operation, ignition misfires, damaged transmission mounts, and components touching the body can produce similar symptoms. This basic test is intended for conventional rubber or hydraulic engine mounts. Some newer Mercedes-AMG models use electronically controlled dynamic engine mounts and may require model-specific diagnostic procedures.
Replacement Engine Mounts
If you need new engine mounts at a fraction of the dealer prices, check out these sites:
- Amazon Parts Catalog
- Your Car Parts: Amazon Garage
- Advance Auto Parts: buy online and pick up at the store
Need to replace the mounts? See our Mercedes-Benz engine mount replacement guide, and for the transmission mount, see how to replace the transmission mount. Verify the correct part number by VIN before ordering because fitment varies by model, engine, drivetrain, and production date.
Rule Out a Misfire First
A misfiring cylinder shakes the engine at idle in a way that feels exactly like a failed mount, so check for one before you buy parts. A scanner shows stored misfire codes and the misfire counter for each cylinder, which tells you whether the vibration is the engine running rough or the mounts letting normal movement through. The UCAN-II Pro reads both, and on AMG models with dynamic engine mounts it can also read the mount control faults. If you do find a misfire, see Mercedes engine misfire problems.
Before you buy parts, scan every control module, not just the engine. It shows the root fault behind the warning lights and tells you whether the problem is still active. See how to do a full health check.
