Leaking shock absorbers are an MOT test fail
The most frustrating thing about shock absorbers and struts, (which are basically the same thing) is that they are sealed units and although they are classed as maintenance free, they will
very often start to leak. In some countries shock absorbers are known as dampers, because that is exactly what they do they damp down and level out the bumps that your car is picking
up as it drives along the road.
Depending what the model of your car is, then the shock absorbers should be changed at certain mileage intervals,
If you are not sure what this is then you can perform a simple bounce test. All you have to do is to press the corner of your car a few times with your body weight and then stop the bouncing. Once you stop then your car should settle back down straight away, if it bounces again more than twice then the shockers require changing. You do this procedure on each corner, bouncing the car and then releasing it.
In my opinion this is not a very satisfactory way of checking your shock absorbers, but at the moment I have not seen a satisfactory machine that will do the job. The best machine that I ever saw and consequently bought was a tester that was sold by SUN equipment. You drove the car onto vibration plates, which shook the cars suspension very violently and then suddenly stopped. The action of the shock absorbers was then recorded on to paper printouts via an ink needle, similar to the ones used in hospital heart machines. If the pattern was tight then the shocks were good, if they were wide, then the shocks needed replacing.
This was a great machine because it produced a print out so that the customer could see the state that his shocks were in. ironically the machine was scrapped by Kwik-Fit after I sold them the business and I don’t think that they are made any more.
How do Shock Absorbers work?
Some cars never have their shocks replaced, but with age the ride of your car will get bouncier and the cars steering will be all over the place when cornering, although this is sometimes
blamed on the cars tyres it is more often than not the shocks that need changing.
As I have said earlier, the most common problem is the fact that they leak oil. If this is the case then they will need changing. Any kind of shock absorber works on the same basis. There is a piston rod that enters a chamber that is filled with oil. The piston has oil seals to prevent leakage. As the piston is compressed by the weight then it takes the force of the road surface and the car. Your shocks take all the up and down pressure (bumps) and the cars chassis remains level, or as level as possible whilst driving along.
When the shocks are worn or broken then you will get an uneven ride in your car. I think that the worse culprits of this are on cars that are used as Taxis. You can often feel the older cars bouncing up and down as you drive along, and apart from alcohol, I am convinced that this is one of the reasons that people are sick in the back of a Taxi.
Struts are normally fitted at the front of cars and are fitted inside a coil spring unit.
These are known as McPherson struts and just like the shock absorbers, they can leak oil. These struts along with the springs that they are inserted into can very often break, and the symptoms are rattling and banging noises coming from the car when going over bumps in the road, This is another problem that the potholes can cause. “Broken springs”
An old perennial that keeps cropping up is that when a shocker has to be replaced then should they be replaced in pairs. In my opinion this is a grey area, the manufacturers always recommend that you fit two, and I think that this is the perfect scenario, but in practice the customer wants to get away with having to spend as little as possible and in general only has the one fitted. The rule to this is simple, if your car is relatively new, then just change the one, the one on the other side should still be good, but if the car is an older model then you should change the shocks on each side of the same axle, backs or fronts. This will give you an even ride and more stable cornering.
Normal shocks are fairly easy to change for the home mechanic
But the struts are more difficult and require some special tools, such as spring compressors and so I would take your car to a local garage, for the work doing.
Pellon Tyre and Auto-centre offer car and van servicing and repairs to all makes of vehicles. We are members of Unipart Car Care centres and give a nationwide guarantee for all our work and parts.