Are you asking about both or one or the other? They do totally different things. Coil springs hold the car up. They fail in one of two ways. There is a special painted coating on them. Once that cracks off, the metal starts to rust. When that gets bad enough a coil can break. Depending on where it breaks, a sharp end can tear through the sidewall of the tire and lead to a crash. If the break is near the top or bottom, it is more likely to just cause that corner of the car to sit low.
The much more common failure is for them to sag with age. All tire and alignment shops have small books that show every car model, where to take measurements on the front and rear, and the range of measurements that is acceptable. Alignment specialists get very picky about those measurements. Cars like yours are more forgiving, but older models that use upper and lower control arms can be adjusted to perfect alignment but they will still have horrendous tire wear and poor handling when ride height is not correct. That is because those alignment numbers only pertain to a car that is standing still on the alignment rack. Since the suspension geometry is wrong, the wheels go through the wrong arcs and movements as they travel up and down. The only way to lessen the resulting tire wear is to make the ride height correct, and that involves replacing weak springs. Vehicles that use torsion bars can be adjusted to achieve the correct ride height. Coil springs must be replaced.
Shock absorbers only create resistance to changes in ride height. They reduce the tendency for the car to bounce when it hits bumps. They do that by forcing oil to travel back and forth through a very small restriction. The most common failure is when the oil leaks out through the seal at the top where the movable shaft comes out. That just leaves air to travel through the restriction, and it can do that very easily. Besides the uncomfortable bouncy ride, that can allow the tires to bounce off the road and lose traction. That causes a loss of steering and braking ability.
Struts are just giant shock absorbers that are strong enough to be used as a structural member to hold the spindle in alignment which holds the wheel straight up and down. A McPherson strut combines the strut with the coil spring around it into one small assembly. Those are popular with small front-wheel-drive cars because it leaves room for the engine and transmission. Your car uses McPherson struts on the front. I found listings for shock absorbers and McPherson struts for the rear. It appears to depend on whether your car is a front-whee-drive or an all-wheel-drive model but there might be other variables.
Thursday, January 24th, 2013 AT 8:30 AM