Worn engine and transmission mounts can be the cause of clunks, thumps and vibration. The purpose of the motor and transmission mounts, besides holding them securely is to insulate the vibration from the engine and transmission from the uni-body or frame of the vehicle. In fact some manufacturers even call them insulators NOT motor mounts. Sometimes motor mounts can be collapsed, greatly reducing their ability to absorb vibration from the engine. Collapsed mounts are the hardest to diagnose, since the rubber does not have to appear worn. Usually when checking engine mounts, one person will be in the driver’s seat power braking while another very trusting individual checks for excessive movement in the mounts!
Looking at the mounts with a light while power braking in drive and reverse is typically done since broken mounts can allow for more movement in one direction or the other. Another way to check for worn mounts is to rock the car back and forth with your knees on the bumper – this is a quick check that’ easy to do by yourself with the engine off and the car in park. If you choose to check the mounts this way, make sure that the hood is supported well. On more than one occasion, I’ve caught the car hood when it was closing because of weak hood supports. Some motor mounts can be visibly checked for worn or split rubber without the need of torquing the engine back and forth.
When changing motor and transmission mounts, the car should be supported by a floor jack and a block of wood or supported from above with an engine support bar. I’ve also used jack stands and jack screws under the car whiles it’s up on the lift.
Tools Needed to Check & Change Motor Mounts
- A good flashlight or drop light.
- Floor jack and/or jack stand.
- Vehicle lift is nice but not always necessary.
- Jack screw if working with the car on a lift.
- Hand tools like wrenches, sockets, ratchets and extensions.