A MacPherson-strut-type front suspension. The strut incorporates a damper and coil spring.
Almost all joints and pivots in a modern suspension system have rubber or plastic bushes, with the possible exception of steering swivel joints.
Because of the constant movement of the suspension parts, the bushes gradually wear out, soften and perish.
Oil contamination also causes them to deteriorate, and if they are allowed to deteriorate too much, they become loose and the steering and roadholding suffers.
It is essential to make a regular check on the condition of all joints in the suspension system.
If you find any joints or pivots to be worn or damaged, replace them (See How to replace anti-roll-bar bushes) or have them replaced at a garage as soon as possible.
If any are found to be contaminated with oil, find the source of the leak and repair it, otherwise any new bushes fitted will be affected.
Examination of suspension parts can often be carried out with the wheels still on, but on some cars you may have to remove them. Wheels must be on for some checks.
Support the car securely on axle stands under chassis members. The force used to lever various suspension parts can easily topple a car that is not securely supported.
If you have only two axle stands, raise one end of the car at a time.
Check the wishbone joints where they pivot at the inner ends, and also the moving joints and pivots at the outer ends of the wishbone and track-control arms where they are fixed to the steering swivel members, or suspension legs in the case of MacPherson struts (See How car suspension works).
Wipe road dirt and grease from all the joints and pivots, and clean around the mounting brackets. Check for corrosion at each point (See Cleaning the outside and checking for rust).
If the rubber bushes are distorted, perished, cracked or contaminated by oil, they must be replaced. Some you can replace yourself, others should be replaced at a garage.
Check around the mountings for signs of rust or damage, probe load-bearing areas with a screwdriver and tap them with a small hammer to make sure they are sound.
Any rusted metal should be treated with a proprietary anti-rust fluid and repainted (See Eliminating rust before painting). If it is badly corroded, it must be replaced at a garage, which may be able to weld in reinforcing plates. Otherwise, the suspension mounting may break loose.
Ask a helper to put a stout lever under each front wheel in turn and lever upwards, while you watch both the inner and outer joints of the wishbone or track-control arms.
Look for any movement other than the normal pivoting motion.
If you see any movement inwards and outwards, examine the joints and bushes closely — they should not move. Use a lamp in dark, underwing areas.
With MacPherson struts, look at the mounting at the top of the inner wing panel. Check for corrosion, which is a common problem with older cars.
Open the bonnet and bounce the front of the car up and down while watching the rubber bush at the centre of the strut mounting. The bush should barely move.
If any flexing is seen, the bush should be replaced. Even if there is no flexing, check also the condition of the bush itself. Look for perishing and cracking, and replace the bush if it is not perfect.
On front-wheel-drive cars, check the condition of the constant-velocity joints on each drive shaft (See How to check U-Joints).
The joints are usually protected by rubber gaiters. Wipe each gaiter clean and inspect it. If you find splits, have the gaiter replaced at a garage.
A damaged gaiter allows the oil or grease to escape and dirt to enter the joint; this causes excessive wear, and replacing the joints is expensive.