Suspension: Strut Assembly
A strut is a shock absorber and a coil spring combined. This system was design by Earle S. MacPherson in 1947 and is now the most commonly used independent suspension found on vehicles today.
A strut like a shock absorber prevents the coil from oscillating after it hits a bump in the road. It prevents this unwanted spring motion by forcing hydraulic fluid through tiny holes in a piston located inside its chamber. This restricted fluid prevents sudden movement and helps isolate the chassis and passenger compartment from the irregular road surface. It provides resistance on both its compression cycle and its extension cycle. Without this dampening effect the vehicle would feel like its floating down the road.
Perform a bounce test on the vehicle to see if a shock absorber or strut requires replacement. Push downward on each bumper with sufficient force to bottom the absorber in its bore. After the bumper is released the upward movement of the chassis should end with just one upward bounce. If more than one bounce occurs the replacement of the shock absorber or strut is in order.
Typically when replacing struts the coil 
spring is reused and the shock absorber/spring seat portion is replaced. A special tool is required to compress the spring. Most shops and dealerships will have one mounted on the wall. An inexpensive pair of strut spring compressors can be used as well. Be careful, safety first. When removing the strut from the vehicle be careful to check for any camber adjustments that can be made. If an eccentric camber bolt is found mark its position before removal. Adjust both camber and toe when replacing this type of strut. Always use great care when releasing a coil springs tension as it contains a considerable amount of energy.
