Why Do Motor Mounts Break?

Motor mounts break down over time due to age, wear, oil contamination, excessive vibration, and driving conditions. It is common for engine mounts to need replacement by 100,000 miles.

This article examines why motor mounts fail, signs of bad mounts, and how to prevent premature failure. We discuss the leading causes such as material wear, oil leaks, engine vibration, hard-driving, and accidents.

Symptoms like increased vibration and steering issues are explored. Preventative steps including maintenance, avoiding contamination, and installing reinforced mounts are recommended. The article provides an in-depth look at motor mount failure to help drivers understand and address this common issue.

Why Do Motor Mounts Break?

Motor mounts are rubber or hydraulic components that connect the engine and transmission to the frame of a vehicle. They are designed to dampen engine vibrations and noises while allowing some movement from torque and shifting forces. Over time, motor mounts can break down and fail due to wear, leakage, or excessive stress. A broken motor mount can lead to severe vibration, steering and handling issues, and even engine misalignment.

Common causes of motor mount failure

Age and wear

Like any rubber or hydraulic component, motor mounts naturally degrade over time. The constant engine vibrations lead to material fatigue and drying out of the rubber. After 60,000 to 100,000 miles, most motor mounts need to be replaced. Higher-performance vehicles or abusive driving can accelerate wear.

Oil leaks

Motor mounts can be contaminated by oil leaks from the engine, transmission, or power steering system. Oil causes the rubber to soften and swell, accelerating failure. Even small leaks near the mounts can dramatically shorten their lifespan.

Excessive engine vibration

Too much vibration from a rough-running engine can overload motor mounts. This is common with very high horsepower builds or modified engines. Upgraded polyurethane mounts may be needed for stiff engine calibrations.

Hard driving or off-roading

Aggressive driving over bumps and turns stresses engine mounts. Off-road driving is especially demanding. The jolts and impacts can fatigue and crack the rubber. Upgraded mounts may be needed for recreational off-road vehicles.

Accidents or collisions

Even minor front-end collisions can bend the frame and damage motor mounts. The mounts bear the brunt of crash forces transmitted forward. Visually inspect mounts after any major crash.

Signs and symptoms of broken motor mounts

• Excessive engine vibration: Badly worn mounts allow an unsafe amount of engine movement. This leads to noticeable vibration through the chassis at idle. Vibration worsens with acceleration.
• Clunking noises when shifting gears or accelerating: With damaged mounts, the engine can torque and clash against the frame when shifting gears. This causes a sharp clunking or banging noise.
• Difficulty steering: If the steering rack mount breaks, the steering system loses its stable platform. This can cause vague, wandering steering feel and difficulty holding the wheel straight.
• Decreased performance: Worn mounts allow wasteful engine movement instead of transferring torque to the wheels. Acceleration and shifting precision suffer.
• Misalignment: A broken mount can let the engine twist and sag. This misaligns components like the drive belts and axles. It can lead to failures.

How to prevent motor mount failure

• Keep the engine oil clean and at the proper level: Prevent oil from contaminating the mounts by fixing any leaks early. Maintain the engine oil level. Dirty oil and low oil accelerate wear.
• Avoid hard driving and off-roading: Limit aggressive driving over bumps and rapid acceleration and braking. Install reinforced mounts if regularly off-roading.
• Get regular inspections and maintenance: Have mounts inspected around 60,000 miles or if any symptoms appear. Replace worn mounts in sets for even support.

Which engine mount fails first?

The passenger side mount typically fails first. This mount handles more engine torque as it is on the transmission side. The added stress makes it prone to earlier wear and tear.

Can motor mounts become loose?

Yes, rubber engine mounts can become loose over time. The rubber compounds slowly soften and lose their stiffness. This allows excessive engine movement and vibration.

Are broken motor mounts expensive?

Replacing broken motor mounts can cost $200-600 for a typical 4-cylinder engine. The labor time is 1-3 hours. Luxury and performance cars often have pricier mounts costing up to $1000 or more.

How common is it for engine mounts to break?

It is quite common for at least one engine mount to need replacement by 100,000 miles. Certain high stress mounts may need replacement as early as 60,000 miles. Our article “How common is it for engine mounts to break?” goes in-depth on the causes, symptoms, and prevention of motor mount failure.