Worn engine and transmission mounts can be the cause of thudding, knocking and vibration. The purpose of engine and transmission mounts, in addition to holding them securely, is to isolate engine and transmission vibration from the vehicle body or frame. In fact, some manufacturers even call them isolators, NOT motor mounts. Sometimes the engine mounts can be collapsed, greatly reducing its ability to absorb engine vibrations. Collapsed mounts are the most difficult to diagnose, as the rubber doesn’t have to look worn. Usually when engine mounts are checked, one person will be in the driver’s seat braking while another Very confident individual excessive movement checks on mounts!
Watch the mounts with a light while braking hard in drive and reverse, as broken mounts can allow more movement in one direction or another. 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’s easy to do yourself with the engine off and the car parked. If you choose to check the mounts this way, make sure the hood is securely attached. On more than one occasion, I have snagged on the car’s hood as it was closing due to weak hood supports. Some motor mounts can be visibly checked for worn or split rubber without the need to torque the motor back and forth.
When changing engine and transmission mounts, the car should be supported by a floor jack and block of wood or supported from above with an engine support bar. I have also used jack stands and jack screws under the car while it is on the lift.
Tools needed to check and change engine mounts
- A good lantern or hanging lamp.
- Floor jack and/or jack stand.
- The vehicle lift is nice but not always necessary.
- Jack screw if you work with the car in a lift.
- Hand tools such as wrenches, sockets, ratchets and extensions.