When your car’s engine is running, there all sorts of metal things – like pistons, crankshafts, cams, rotating and pounding away. It should be of little surprise that the engine tends to move around a bit during operation. Fortunately, you won’t feel any of this because all the movement and vibration is absorbed by your car’s engine mounts. The problem is, motor mounts don’t last forever. After a while, the rubber in many mounts deteriorates and when this happens, you may start to hear odd noises when you drive. For example.
When your car and motor mounts are new, the inside of your passenger cab should be whisper quiet. Acceleration will be smooth and engine noise will be minimal. When your car starts to get older, your previously noiseless interior may start to be infiltrated with soft, drumming sounds. This sound will be evident whether your car is idling or moving. In many cases, it will get louder when your engine is spinning faster. This may be an engine mount starting to fail.
Another symptom of failing motor mounts is a thump or clunk when you hit the gas. This occurs because your engine actually raises up several inches in the engine bay when you accelerate. And when you let off the gas, it falls back into place with a thump. If it’s a really loud thump, your motor mounts are probably broken.
There are all sorts of types of motor mounts. The original old-style mounts are just a sandwich of two metal mounting plates with a pad of rubber inside. One plate mounts to the engine, one to the body and the rubber in-between dampens the engine vibration. If you ever have to have one of these old style mounts replaced, the mounts themselves aren’t very expensive but sometimes they can be very hard to get at and thus labor fees can be high.
A slightly more sophisticated mount is called a hydraulic motor mount. These have a fluid inside which really helps to dampen any engine vibrations.
Fancy motor mounts
A few automobile manufacturers have gone high-tech with their engine mounts. Audi, for example, has “active mounts” that can change their stiffness based on RPM. The mounts provide a soft cushion at idle, but when you hit the gas, they stiffen up. In effect, the action of the motor mounts is tuned to the RPM of the car engine yielding a very quiet ride.
An even more sophisticated technology is Magneto Rheological (MR) mounts. These cutting edge mounts use a special rheological polymer that changes damping characteristics according to applied magnetic fields. The folks at East Hills Chevrolet (Douglaston, NY) tell us the MR motor mounts are on the way for the Corvette models.
What to do if you suspect your mounts are bad?
If your car has over 100,000 miles on it, start paying attention to the way the engine feels, especially when you accelerate. Does it vibrate? Does it thump when you accelerate? If so, bring it to your local mechanic and have them look at your motor mounts. Broken motor mounts can start to damage other engine and drivetrain parts, so don’t delay if you think you may have one.
Earthgarage – Greener Car. Fatter Wallet.