Mechanics

Motor Mount

Motor Mounts
Engine Mounts

Engine mounts are what separate you from the nasty vibrations and harmonics created by the internal combustion engine. Without these simple items, you would feel exactly how rough the engine in your vehicle really is, even when running properly. In this article we will explain what an engine mount is, what it does and why they are necessary for a comfortable driving experience. Engine mounts are basically rubber isolators that are mounted between the engine in a vehicle and the frame. They hold the engine in place while absorbing the vibrations caused by the engine, creating a quiet, smooth feeling inside the vehicle. They are made of rubber to absorb vibration without transferring it, but some manufacturers have tried using a liquid (oil) filled mount to dampen vibration with some success. In some performance applications polyurethane or solid steel mounts are used, these mounts transfer vibration, but can withstand the abuse and high-horsepower applications seen in racing where a comfortable, smooth ride isn’t really an issue.

In a rear wheel drive vehicle there are usually two engine mounts, one on either side of the engine. Front wheel drive applications may incorporate more mounts to help control the torque of the engine, usually one on both sides and one in the front center. Front wheel drive mounts are engineered differently from rear wheel drive due to the fact that the engine is sometimes hanging on them due to space constraints in front wheel drive vehicles whereas a rear wheel drive engine is usually sitting on top of the mounts. Front wheel drives sometimes incorporate a “dog bone” or torque mount, its sole job is to control the torque twisting of the engine so that the other mounts aren’t stressed as much. These torque mounts are a common failure on vehicles that use them.

When an engine mount breaks it can cause many different things to happen; usually you will hear and feel a heavy clunk when accelerating, this is the engine moving around in the engine compartment. Other times the engine vibration may become more pronounced due to the mount collapsing, this will transfer the vibrations of the engine to the frame, thus the interior of the vehicle. This situation can cause the failure of hoses or anything that is mounted to the frame from the engine. It can also cause the throttle to stick on older vehicles with mechanical linkages instead of cables. In front wheel drive vehicles, a broken mount can cause the axle to fail or pop out of the transmission, causing the vehicle to stop moving. 

When one mount breaks it adds more stress to the remaining mounts, and should be taken care of as soon as possible. Many things: oil contamination, hard shifting (manual transmission), excessive high idle, or the combination of age and engine compartment heat can cause engine mount failure. To inspect your motor mounts, lift and support the vehicle. Use a flashlight to see if the rubber has deteriorated or collapsed from the weight of the engine or if they are obviously torn, if so you will need to replace them. If they are oil soaked from an engine or transmission oil leak, the leak should be repaired as well or it will cause the new mount to fail as well.

If you suspect your vehicle is in need of new mounts, they can be found at most parts stores. They should last for many years, unless subjected to abuse from other than normal situations. Be warned, some applications require a wide variety of different tools and equipment to be able to lift and support the engine while replacing the mounts. Most mounts are bolted to the engine and transmission, while others are bolted to the frame of the vehicle. When purchasing new engine mounts for your vehicle, always use an OEM (Original Equipment Manufacturer) or equivalent, less expensive mounts are made of lower quality material and may not perform as well or last as long as the higher quality part will.

If further assistance is needed, our certified car repair technicians are ready to answer your car questions.

Related Car Repair Information

AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


COMMENTS TO THIS ARTICLE


Please use our question form if you have a specific question about your car as we are not able to give you a full answer on this page.



Article first published (Updated 2013-08-19)