Motor Mount

📖 YOUCANIC Automotive Glossary

Motor Mount (Engine Mount)

Motor mounts, also called engine mounts, are components that secure the engine and transmission to the vehicle’s subframe or body while isolating engine vibration from the passenger compartment. A typical vehicle uses 3-4 mounts — two or three engine mounts and one transmission mount. Conventional motor mounts consist of rubber bonded between two metal plates or a rubber bushing inside a metal housing. The rubber absorbs and dampens the engine’s vibrational energy, preventing it from transferring to the chassis. Some vehicles use hydraulic (fluid-filled) mounts that contain a viscous fluid inside the rubber mount, providing superior vibration damping at idle — these mounts have internal chambers and an orifice that controls fluid flow to counteract specific vibration frequencies. Active mounts on some luxury vehicles use electronic actuators to dynamically cancel engine vibration in real time.

Worn or broken motor mounts cause a range of symptoms that are often misdiagnosed as engine, transmission, or exhaust problems. The most common sign is excessive vibration felt through the steering wheel, dashboard, or floorboard at idle — shifting into Drive or Reverse may cause a noticeable thud or clunk as the engine rocks on the failed mount. You may hear a banging or clunking noise during acceleration, deceleration, or when going over bumps as the engine shifts and contacts surrounding components. A broken mount can also cause the exhaust to contact the undercarriage (creating a rattle or buzz), accelerator cable or throttle linkage binding, radiator hose stress and coolant leaks, and in front-wheel-drive vehicles, CV axle angle changes that cause vibration or clicking. DIYers can diagnose failed mounts by having an assistant put the vehicle in Drive with the brake firmly applied while you observe the engine from the side with the hood open — if the engine lifts or rocks excessively on one side when the assistant gently applies throttle, the mount on the opposite side (the loaded side) is likely failed. Check hydraulic mounts for fluid leaking from cracks in the rubber. When replacing mounts, always support the engine from below with a jack and wood block before removing any mount bolts, and replace all mounts at the same time if multiple mounts show deterioration — a single new stiff mount paired with old soft mounts shifts stress to the new mount unevenly.