Toyota-Lexus-Subaru-Honda Engine Mounts

The engine mounts serve a couple of purposes. First of all, they serve to locate the engine in the proper place in the engine compartment and in proper relationship to other components. For front wheel drive vehicles, it keeps the engine and transaxle in proper alignment with the drive axles as you’re accelerating and putting power to the wheels.
For rear wheel drive vehicles, it they keep the engine from tipping forward and chopping a hole in the radiator with the fan. A second purpose of the engine mounts is to insulate the rest of the car and the passengers from the engine’s vibrations.

As the engine mounts get old and hard they tend to increasingly transmit vibrations that are felt by the passengers. Engine vibrations are also more likely to be felt if the car is involved in an accident where things get skewed so that the engine isn’t quite in proper alignment and the engine mounts are under tension.

Some engine mounts have a fluid portion of their core, and if the fluid leaks out and the mount collapses as it ages, then this will result in more vibrations being passed on to the rest of your Toyota, Lexus, or Scion as well.

Every time you accelerate, the engine tries to twist out of position and rotate in the opposite direction that the wheels are rotating (front wheel drive cars) or the opposite direction that the driveline is rotating (rear wheel drive vehicles). Eventually the mounts may tear loose as a result of the cumulative stresses.

When they do tear loose (or collapse with the fluid filled mounts) it allows the engine to lift up and shift around quite a bit more than normal. When this starts happening, it’s not unusual to feel a clunk every time you’re on and off the gas when in first gear. If you open the hood and have someone put it in gear and briefly accelerate while holding their foot on the brake you can see the engine lift up and then settle back down each time they’re on and off the gas.

A broken engine mount doesn’t result in your engine falling out on the road. It will result in extra movement, which puts other surrounding components under more stress. The remaining engine mounts will be under more strain and will be more apt to tear as a result. Hoses and electrical harnesses-every thing that bridges between the engine and the surrounding engine compartment will be repeatedly flexed more than they were designed to withstand, with the possibility of being fatigued until they break.

The axle constant velocity joints will be under greater strain as they are operating out-of-position at greater angles than intended. The bushings that the axles engage with in the final drive portion of the transaxle will experience greater sideways pressure and be more apt to wear. The air intake tube that pipes air from the air filter housing to the throttle body of the engine is far more likely to crack and split open. I’ve never personally seen this, but in certain cases it can cause unintended acceleration if the engine shifts in such a fashion as holds the throttle open.