What are the symptoms of a bad motor mount?

Some of the symptoms of a bad motor mount include breaking of the mount, thumping noises and stressed components such as wiring connectors, heater and radiator hoses and the exhaust system. In a rear-wheel-drive application with an engine-driven fan, a bad mount can allow the fan to knock the radiator.

A loose or broken motor mount in front-wheel-drive application can cause serious problems, since it may allow engine movements that might interfere with shift linkage or throttle. Extreme aft and fore rocking of the transverse-mounted engine causes exhaust leaks where the head pipe connects the manifold or the head pipe itself fails.