Motor Mounts: What Are They and What Do They Do?

By Karen Johnston June 21, 2019

Quick facts

Most vehicles have three to four engine and transmission mounts securing the powertrain.
Failed motor mounts can allow the engine to shift several inches during acceleration or gear changes.
Fluid-filled motor mounts provide better vibration damping than solid rubber mounts.
Engine movement from failed mounts can stretch wiring harnesses and misalign driveshaft angles.

Essentially, motor mounts are typically made of rubber or a fluid-filled rubber that are bonded to metal brackets that bolt to the engine and frame of the vehicle. They are designed as insulators that support, hang, or cradle the engine and transmission assemblies. There are usually 3 to 4 engine/transmission mounts on a vehicle.

Over time the rubber can deteriorate, crack, split, harden, compress, and leak fluid. This reduces the motor mount's ability to insulate engine vibrations and engine torque.

The resulting factors are that the engine can move several inches especially on acceleration and deceleration, or changing of gears between drive and reverse. This gives the potential for misalignment of axle shafts, drivelines, and interference with rotating versus stationary components and stretching of wiring harnesses for the engine.

Some of the symptoms associated with worn motor mounts are:

Increased vibrations, noises, clunks, and erratic engine movement when the transmission is engaged in drive or reverse.

If you are experiencing some of these symptoms, we recommend having an inspection done by one of our Qualified Automotive Technicians and having the repair that is recommended performed in our clean and professional shop in Gresham. We look forward to being your family's trusted choice for auto repair and service. Be sure to go to our Shop Specials section on our website for our current promotions and specials.

Happy Motoring!

Frequently asked questions

Common questions

How do I know if a clunk or vibration is coming from a motor mount versus another source?

Motor mount symptoms are most noticeable during gear transitions, particularly when shifting between drive and reverse at a stop, or during hard acceleration from a standstill. If the clunk or vibration is most pronounced at those specific moments and diminishes at steady highway speeds, motor mounts are a strong suspect. Vibrations from other sources like CV joints or driveshafts tend to be speed-dependent rather than load-dependent, which helps a technician differentiate them during inspection.

Can worn motor mounts damage other parts of the vehicle if left unrepaired?

Yes, and the damage can extend well beyond what the mounts themselves cost to replace. When the engine shifts position excessively, axle shafts can angle beyond their designed range, accelerating CV joint wear. Coolant hoses, vacuum lines, and wiring harnesses are stretched or chafed against adjacent components. In front-wheel-drive vehicles with transverse engines, mount failure can bring the engine close to interference with the radiator or firewall during hard acceleration. The longer worn mounts are ignored, the broader the collateral damage.

Is it safe to drive with worn motor mounts?

For a short distance at low speed, yes, but it is not advisable as a long-term situation. Worn mounts allow powertrain movement that stresses every component connected to the engine, the exhaust system, drive axles, hoses, and electrical connectors all bear load they were not designed to handle. The vibrations transmitted to the cabin also increase driver fatigue. Most importantly, severely failed mounts can allow the engine to contact the firewall or radiator, causing sudden and serious damage.

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