Why A Bad Engine Or Transmission Mount Gives Me The Shakes!
One of my favorite things about having an auto repair shop is the ability to see many different cars in many different conditions. I get the opportunity to meet many people who have different needs and expectations of their cars. Every week, I take time to review every work order. That sounds a bit crazy, right–every work order…Hear me out for a second. As I look over the work orders, the repairs, and the DVIs (Digital Vehicle Inspections), I see things that tend to stand out more than others. Over the past few weeks, I have noticed an uptick in engine and transmission mount deterioration.
What Is An Engine Or Transmission Mount?
If you have ever been in a car accident, you may have heard the term car frame. The frame is a structural component of the car. Some cars have subframes and cradles. The engine and transmission nestle in these frames. The mounts secure the engine and transmission to the car’s frame. Engine and transmission mounts provide stability, absorb vibration, and reduce noise. Most mounts are rubber and metal. Some are hydraulic. This means they use fluid inside to dampen vibration, like a shock absorber. Some cars use an active mount design. These have electronic sensors and adjust in real-time to optimize performance.
Clunk and Jerk
No, those are not two characters from a kid’s cartoon. Those are signs that you have a weak or broken mount. Let me give you an example. You start your car. You shift your car from Park to Reverse–CLUNK! You shift your car from Reverse to Drive–JERK!
Typically, the mount is made from a combination of metal and rubber. One part attaches to the engine or transmission. The other part attaches to the frame. When the rubber tears or detaches, there is more movement than there should be. Instead of being held fixed in the frame, the biggest parts of your car move–and they can really throw their weight around.
Think about all the power that your engine and transmission have. From a client perspective, you step on the gas pedal and go, right? Have you ever had a water bottle or drink in your cup holder and watched how the fluid changes position when you accelerate or decelerate? It’s like you are tipping your drink one way or the other. That is what happens to the engine or transmission. They tip or rock back and forth, or side to side, depending on which mount is failing.
Why Do They Fail?
Like everything in your car, mounts go through normal wear and tear over time. My driving area is considered severe. Here, the average driver experiences extreme summer an winter temperatures, stop-and-go traffic, and poor road conditions. The constant exposure to heat, road vibrations, and environmental factors leads to deterioration.
Something else I see is collateral damage. For instance, did you know fluid leaks from a power steering system erode rubber components? Bushings, hoses, and (you guessed it) mounts lose durability and break down. The detergent value in the fluid eats away at rubber, like acid. As one mount starts to fail, the others become strained.
Speaking of collateral damage, think about this extra movement in the engine compartment. Your engine rocks every time you shift gears, accelerate, or stop. Think of all the hoses, wires, and other parts that are attached to the engine and transmission. I read a Technical Service Bulletin that shared a reason for an engine misfire. A broken motor mount caused a loose connection in an ignition wire. Not a bad spark plug. Not a bad wire or an ignition coil. A bad motor mount stressed the ignition components and interrupted the connection.
What Can You Do?
Here is what I hope you take away from this. I would like you to be able to recognize symptoms like increased vibrations and clunking noises. Pairing this knowledge with routine maintenance and visual inspections (like my shop’s DVI) can catch your mounts before they fail, preventing further damage. As always, stay well my Automotive Family. Safe travels and cheers to a smooth ride!
Grease In Her Veins 
Always useful information from you. Awesome.
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