A Car That Shakes While Waiting At A Red Light: Tired Engine Mounts Often Mistaken For A Failing Engine

A vibration that reaches the steering wheel and seats while the car sits in Drive is often blamed on the engine. Very often, though, the cause is simply rubber engine mounts that have hardened with age and heat.

Many drivers know the moment well: the light turns red, the car stops with the transmission in Drive, and the steering wheel, floor, and seats start to buzz. Move the lever to Neutral or Park and the vibration fades. Owners often blame weak spark plugs, a dirty throttle, or an engine that is "getting tired." In many cases the engine is perfectly fine. What has worn out are the engine mounts, the rubber cushions that hold the engine and transmission to the car's body.

Engine mounts act as dampers. An engine always vibrates while running, and the rubber in these mounts absorbs that movement so it does not travel into the cabin. Rubber does not last forever, though. Engine bay heat, oil seepage, the torque load every time the car accelerates, and rough roads slowly harden, crack, or tear it. For cars that spend a lot of time in city traffic, the symptoms may appear after five to seven years or around 80,000 to 100,000 km, although this depends heavily on how the car is used.

The signs are fairly easy to recognize. The vibration is strongest while stopped in Drive or with the air conditioning running, because the engine is carrying extra load. You may hear a "clunk" or feel a jolt when pulling away, reversing, or shifting from Park into Drive or Reverse. In a manual car, the jolt shows up when releasing the clutch or lifting off the throttle suddenly. Under the hood, the engine visibly rocks too much when revved briefly with the brakes held.