Faulty motor mounts, which many technicians overlook entirely, often affect a vehicle's overall performance and personality, undercar service experts said. Furthermore, successful technicians understand two things about motor mount diagnosis: First, never underestimate teh value of a thorough visual inspection; Second, although ban mounts cause a wide variety of problems, the symptoms usually have one train in common - they vary according to engine load.
A typical motor mount has two metal mounting points separated by a durable piece of rubber. One metal mounting point is bolted to the vehicle's frame, the other bolts directly to th engine.
Some engines also have a dog-bone shaped stabilizer link (commonly called a "dog bone") that helps limit fore-and-aft engine movement. This link, which is bolted between the engine and frame, has a rubber insulator at each end.
The rubber part of the mount must perform two almost conflicting tasks.
First, it has to remain resilient enough to insulate normal engine movement and vibration from the vehicle's frame and body.
Second, the rubber insulator must be firm enough to limit engine movement and vibration from the vehicle's frame and body.
Second, the rubber insulator must be firm enough to limit engine movement during normal vehicle operation.
Factors such as underhood heat, ozone, engine maintenance and driving conditions impact the longevity of engine mounts. For example, heat eventually fatiques the mount's rubber insulator, causing it to sag, shift or split. So, vehicles driven strictly in the city may wear out mounts sooner due to the relatively higher underhood temperatures resulting from stop - and - go driving.
Poorly miantained engines tend to misfire and run roughly. The rougher the engine runs, the stronger the vibrations it creates. Teh stronger teh vibrations and the lkonger teh enging remains untuned, the greater the wear and tear on the mount's rubber insulator. eventually, escessive engine shake translates into premature insulator mailure. What's more, oil leaks are commonplace on poorly maintained vehicles. When oil leaks onto a motor mount, it eventually softens the insulator, spurring premature failure.
The symptoms of faulty motor mounts mary according to the vehicle and the severity of the problem. For instance, the symptoms of a split or cracked insulator are more ovbious and severe than those caused by a fatigued, soggy one.
The easiest way to approach this broad topic is to understand the two basic consequences of broken or fatigued motor mounts:
First, they allow excessive powertrain (engine and transmission) from its original location;
Second, they allow excessive powertrain movement to occure, affecting everything attached to or mounted near the vehicle's powertrain system.
For example, the following components can tolerate only a certain amount of powertrain movement before trouble begins:
cooland hoses; air condition hoses;
transmission cables or linkage;
clutch cables or linkage;
air intake ducts; and electrical wiring.
When faulty motor mounts dislocate the powertrain or allow undue engine movement, exhaust parts may begin banging against the body or frame, especialy whenthe driver accelerates suddenly.
a typical front-drive vehicle has a flexible exhaust joint between the exhaust maniforl and exhaust pipe. Worn or borken enging mounts may cause premature exhaust joint failure or create exhaust vibrations by binding this joint.
Many exhaust systems have stainless-steel, sheet-metal heat sheilds surrounding he catalytic converter. Eventually, motor mount problems may create exhaust vibrations by binding this joint.
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