Symptoms of Failing Motor Mounts

As motorists, we often focus on the heart of our vehicles – the engine and transmission. A major issue with these vital components can leave us stranded. However, we sometimes overlook the crucial structural parts that support these powerhouses. Among these unsung heroes are the engine or motor mounts. These assemblies not only bear the engine's weight but also crucially prevent engine-generated vibrations from reaching the car's chassis. Along with transmission mounts, they are fundamental to the structural integrity of your powertrain. When an engine mount fails, a cascade of symptoms and secondary problems can arise, leading to a host of issues. Fortunately, many of these symptoms are relatively straightforward to identify, allowing for prompt repairs.

What Exactly is an Engine Mount?

An engine mount is a specialised component designed to secure an engine in its precise position within the engine bay, eliminating unnecessary play or movement. Engine mounts vary significantly in style and configuration depending on the vehicle's make and model. However, most share common characteristics. The vast majority of modern engine mounts incorporate a rubber isolator. This rubber element is sandwiched between the engine itself and a fixed point on the vehicle's rigid structural supports. This design serves a dual purpose: it restricts excessive engine movement and, through the isolator, dampens vibrations, preventing them from transferring to the chassis.

How Many Motor Mounts Does a Car Typically Have?

While most engines are supported by two to three motor mounts, the majority of transmissions rely on a single transmission mount. The precise number of engine and transmission mounts can differ between vehicle makes and models. Manufacturers consider several factors when deciding on the number of mounts, including the weight of the engine and transmission, their orientation, and the type of mount being used.

Spotting the Signs: Symptoms of a Bad Motor Mount

A faulty, worn, or damaged motor mount often manifests through several noticeable symptoms, some more severe than others. Recognising these can be invaluable for expediting repairs.

1. Significant Vibration

As motor mounts degrade, you'll likely experience a noticeable increase in engine vibration within the cabin and through the steering wheel. This is due to the diminishing damping capabilities of the worn mounts. This vibration tends to worsen as the wear progresses. It's important to note that this type of vibration can feel more severe than issues caused by a bad CV joint or a faulty tie rod.

2. Unusual Noises

Worn motor mounts, with their increased free-play, can produce harsh "clunking" or "thumping" sounds. These noises typically occur when the engine's weight shifts considerably during acceleration. Like other symptoms, these noises generally become more pronounced over time.

3. Irregular Movement Under Acceleration

When one or more engine mounts begin to wear, you might perceive a shifting sensation from the front of your vehicle during acceleration. This is a direct result of excessive engine or transmission movement under heavy powertrain load. In many cases, this increased movement can accelerate the wear on the remaining engine mounts.

4. Potential Engine Damage

In the most extreme scenarios, excessive movement caused by degraded motor mounts can lead to actual engine damage. This can happen if the engine makes contact with the vehicle's frame, sub-frame, or other structural components. Damage of this nature can be costly to repair and, in some instances, could render the engine inoperable.

What Causes Engine Mounts to Fail?

The most common culprit behind engine mount failure is standard wear and tear. Over time, the rubber isolators within the mounts begin to dry out, crack, and degrade. This compromises their ability to control engine vibration and movement, making replacement inevitable. It's also common for additional engine mounts to fail in relatively quick succession once one begins to deteriorate. This is largely due to the increased stress placed on the remaining mounts as one fails.

How Long Do Engine Mounts Typically Last?

On average, you can expect engine motor mounts to last approximately 5 to 10 years before needing replacement. However, some mounts can last considerably longer, even throughout the vehicle's entire service life under favourable conditions. Several variables influence an engine mount's lifespan. The most significant is the road surface conditions the vehicle typically encounters. Engine mounts will naturally last longer when a vehicle is primarily used for highway cruising compared to navigating pothole-ridden city streets.

Can You Continue Driving With a Broken Motor Mount?

It is strongly advised not to drive any further than absolutely necessary with a broken motor mount. While the failure of a single mount might not immediately cause catastrophic failure, continued driving will increase the likelihood of further mount failures. If more than one mount fails simultaneously, the stress on the vehicle's drivetrain can become significant. Any failed motor mount should be diagnosed, identified, and replaced as soon as possible. This proactive approach will substantially reduce the risk of subsequent mount failures and minimise the chance of secondary symptoms developing. If you are not comfortable performing such repairs yourself, schedule an appointment with a trusted service centre at your earliest convenience.

Should Engine Mounts Have Play?

All engine mounts are designed to have a certain amount of controlled play. However, this play should be minimal. This inherent slight movement is due to the rubberised bushings used in most motor mounts, which naturally flex under stress. Nonetheless, any abnormal amount of play or substantial engine movement, especially during high-RPM throttle application, should be a cause for immediate concern. Excessive play typically indicates that one or more motor mounts have degraded, allowing for more movement than would otherwise be present.

Engine Mount Replacement Cost

The average cost for replacing an engine mount typically ranges between £200 and £500. In some rarer cases, this cost can be higher. Of this total, approximately £30-£100 is for the part itself, with the remainder (£170-£400) covering labour costs. Several variables influence the overall replacement cost, including the make and model of the vehicle, the complexity and time required for the replacement, and the hourly labour rate of the chosen repair shop.

Can You Replace Motor Mounts Yourself?

DIY mechanics with the appropriate knowledge and tools can successfully replace engine mounts. This task typically requires a floor jack, jack stands, a 2x2 wooden block (to distribute pressure), and basic hand tools. It is crucial to remain vigilant when supporting the vehicle's engine with a jack to prevent accidental damage to the oil pan. The replacement process generally involves supporting the engine securely with a floor jack and jack stands before unbolting and removing the faulty mount. A new mount is then installed and torqued to specification before the jack is carefully removed.

Should All Motor Mounts Be Replaced at the Same Time?

As mentioned earlier, it's not uncommon for vehicle motor mounts to fail in quick succession after an initial failure. This is due to the added stress placed on the remaining mounts. Therefore, it is generally recommended to replace all engine motor mounts simultaneously. This ensures that all mounts have identical rigidity and that no single mount is subjected to more stress than its counterparts. In the long run, this approach can save you both time and money.

Frequently Asked Questions (FAQ)

Q1: How can I test if my motor mounts are bad?

A simple test involves having a helper gently apply the accelerator while you observe the engine. With the parking brake firmly engaged and the transmission in drive (or reverse for rear-wheel drive), have your helper slightly increase the engine RPM. Watch for excessive rocking or lifting of the engine. You can also try to gently rock the engine by hand (when off and cool) to feel for excessive play or movement.

Q2: Can a bad motor mount cause poor fuel economy?

While not a direct cause, severe vibration and improper engine alignment due to bad mounts can indirectly affect fuel efficiency by causing the engine to run less smoothly and potentially altering air-fuel mixture dynamics. However, this is usually a minor effect compared to other causes of poor fuel economy.

Q3: Is it safe to drive with a broken motor mount?

It is not advisable to drive extensively with a broken motor mount. While one broken mount might not cause immediate catastrophic failure, it puts extra strain on the remaining mounts, increasing the risk of further damage and potential for the engine to shift and cause more serious problems.

Q4: What is the difference between a motor mount and a transmission mount?

Both serve the same purpose of supporting their respective components and isolating vibration. A motor mount supports the engine, while a transmission mount supports the transmission. Often, when discussing powertrain mounts, people refer to both collectively.

Q5: How much does it typically cost to replace all motor mounts?

Replacing all motor mounts will generally cost more than replacing a single mount due to the increased labour and parts involved. Expect costs to potentially double or triple depending on the vehicle and the number of mounts. It's best to get a quote from your mechanic.