(see video below)
An awful lot of engineering goes into a car engine, but arguably one of the simplest components of an engine can cause some of the biggest problems. Engine mounts aren’t technically ‘in’ the engine – they are the components that attach the engine (and the transmission) to the body of the car.
Most cars have three or four engine mounts and one mount for the transmission. Generally they are made of rubber or a rubber like compound although some are liquid-filled hydraulic style mounts.
Apart from fixing the engine into the car so it doesn’t fall out, mounts are primarily there to reduce the transmission of vibration from the engine to the frame of the car itself. They also work the other way around by protecting the engine and transmission from shocks from the car, such as driving over a pothole in the road.
Finally they play a role in aligning the engine in the engine compartment – if alignment goes out of whack, at a certain point the engine may stop working altogether. In many respects they play a very similar role to cartilage in the human body, which protects and cushions the bones from shocks and bumps.
So, in summary, they’re pretty important!
How long do engine mounts last?
As a very general guide, engine mounts last for anything between 60,000-80,000 km before they need replacing (generally at the 5-7 year old mark). Most cars that are under for example 5 years old or around 75,000 km will probably be covered for engine mount failure in the warranty, but you’ll need to check this.
Engine mounts can fail due to the rubber perishing or splitting and you can sometimes see a crack or tear in the rubber. Liquid filled mounts may be leaking fluid. They can also simply wear down, in which case they often appear to sag – this is what can cause misalignment of the engine and sometimes quite severe vibration.
What are the symptoms of worn engine mounts?
The most important symptom to watch out for is a general increase in vibration and noise from the engine, particularly knocking or thudding sounds. It can sometimes be hard to spot this if the sound of the engine hasn’t suddenly changed, as you get used to a slight increase in engine noise anyway as a car gets older, and don’t really notice it. Other possible symptoms include vibration coming through the steering wheel when driving and a rattling noise on starting or stopping the engine.
There are also other things that may be causing engine noise or vibration, such as when a part of the exhaust (or its fixings) has come loose or bent and is banging or vibrating against another part of the engine or the car body.
In more severe cases of engine mount failure (see video above), the engine itself will be bouncing around inside the engine compartment. This is a bad sign and any car where the engine mounts have deteriorated to this degree will be very unstable and unsafe to drive.
It’s also not unusual for more than one engine mount to need replacing. Where one has worn or failed, the remaining mounts have to take the strain and this can in turn make them wear out more quickly.
A similar problem can affect transmission mounts. Although the transmission isn’t as heavy or as subject to vibration as the engine, a worn transmission mount can cause a variety of other symptoms, such as squeaking noises when starting the car or when changing gear.
What’s involved in replacing engine mounts?
Replacing worn or damaged engine mounts is fairly straightforward, however you need a very well equipped workshop to carry out the procedure, as the engine must be lifted up and supported from underneath the vehicle so the engine mounts can be replaced with new ones.
Often it’s only when you get the car back after the engine mounts have been replaced that you realise how noisy your car had been. It sometimes feels like you’ve swapped your car for a brand new one!