Astoria Mechanic | Collision Repair | Tolimas Auto Center

Symptoms of Broken Engine Mounts

Vibrations, Clunking, and Other Symptoms of Broken Engine Mounts

If your car has annoying vibrations at idle and clunks when you accelerate then you most likely have worn or broken engine mounts. As cars age they tend to develop vibrations and clunks. Clunks can be mostly attributed to worn or broken suspension components including mounts. Vibrations are caused by misfires or broken engine mounts as well. Those vibrations are felt throughout your car due to collapsed metal and rubber mounts that attach your engine and transmission to your car’s frame. The internal combustion engine inherently vibrates quite a bit from all the metal moving parts and the internal combustion process. Auto manufacturers tune these vibrations out with the use of engine and transmission mounts.

Old Engine Mount Next to New Mount
Worn mount next to its new replacement

Different Types of Motor Mounts

Most cars have simple engine and transmission mounts made out of rubber which has been bonded to or pressed into a metal casing that bolts on to the frame of your car. This does a good job of dampening engine vibrations while the mounts are in good condition. There are also fluid filled hydraulic mounts which have a chamber inside the mount filled with hydraulic fluid. These mounts are more cushioned and give the car a softer more luxurious feel, but also wear out faster. On fluid filled engine mounts the chamber that holds the fluid will rupture and it will leak out giving this type of mount a much shorter service life. The most modern and expensive type are called active mounts. They are also filled with fluid, but have an electrical connector that uses sensors and valves to change the characteristics of the engine mount. These types of mounts are mostly found in performance and luxury car such as those from Audi, BMW, Lexus, Acura, and Cadillac. Lastly there are aftermarket motor mounts that are made out of polyurethane for stiffness. These are the hardest and transfer the most vibrations into the cabin.

Collapsed Engine Mount
Broken Engine Mount

How motor mounts break

Motor mounts tend to break from a combination age and engine torque. The rubber portion of the motor mounts deteriorates over time. The same way tires dry crack with age, so do engine mounts. As the motor mounts age and get weaker they are less able to tolerate engine torque. This will eventually cause the motor mount to tear and fail. Another less common way motor mounts can fail is due to an oil leak. A slight oil leak won’t cause any major issue as long as the engine is kept with the recommended amount of oil. But if the oil happens to be leaking over a motor mount the oil will cause the rubber to soften and swell making the mount fail prematurely. A failed motor mount will cause excessive vibrations to be felt throughout the cabin at idle and smooth out as your drive or cruise. It can also affect suspension geometry affecting alignment. Broken motor mounts can be easily diagnosed when brake torquing an engine with the hood up. You’ll quickly notice the excessive engine movement seeming like the engine wants to jump out of the engine bay.

Mercedes Broken Engine Mount

Engine Mounts can also be visual inspected as the rubber will start to crack and separate from the metal sleeves that house the mount. If you have the symptoms discussed in this article or have questions about your car, please feel free to Contact Us at Tolima’s Auto Center.

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