A vehicle's motor mounts secure the engine to the frame. In addition to the metal mounts, the motor mount assembly includes a layer of rubber or polypropylene between the mounting points to dampen engine vibrations. As a vehicle ages, motor mounts may loosen. When an engine mount breaks or the dampening material disintegrates, your vehicle will exhibit harsh vibrations and perhaps sustain damage. Check the motor mounts periodically to keep your car or truck in working order.
Symptoms of a broken motor mount may appear when you're driving the vehicle with a normal load. In a rear-wheel-drive vehicle, according to Aa1car.com, you may hear rattling or thumping noises. In a front-wheel-drive vehicle, you may notice trouble shifting or accelerating.
Perform a visual check for excessive engine movement. You will need another person to help because the hood blocks visual access to the engine. Open the bonnet and start the engine. Keep firm pressure on the brake while shifting into drive. Keeping your foot firmly on the brake, apply a little throttle. Have your helper note any excessive engine movement or vibration. If the engine moves more than a half-inch, your car likely has a bad motor mount. Disengage the transmission and put the vehicle in park. Turn off the engine.
The motor mounts reside on the lower half of the engine, between the frame rails. Using a flashlight, inspect the motor mounts for damage. Any cracked or loose rubber between the engine mounts indicates a vibration problem. Replace them as soon as possible. Replace broken-off bolts with original products or those the manufacturer recommends. Be sure to tighten loose bolts to factory specifications.
Using a pry bar, attempt to wedge the tool between the metal portions of the motor mount and vehicle frame. If gaps appear when you move the pry bar back and forth, you may have a broken bolt that you didn't see when you performed the visual inspection.
Perform a visual inspection of any "dog bone" engine mounts holding the top half of the engine in place. These mounts provide extra vibration dampening on front-wheel-drive vehicles. Check the rubber bushings inside each end of the "dog bone" for cracks and deterioration.
Always stay clear of the front of any vehicle whose transmission in the "drive" position. Perform visual inspections from the side of the vehicle.