Inspection and maintenance of automobile leaf springs

Since automobile leaf springs are composed of multiple parts, they may be worn out when used for a long time. Therefore, we recommend that leaf springs should be inspected at least every 20,000 kilometers.

 

Before jacking up the car, we recommend placing it on level ground, making sure the tires are at normal pressure, and the car is at normal vehicle weight with no passengers and a full tank of gas. Crouch behind the car and observe. At this time, both ends of the vehicle should be on the same level. If one end is lower than the other, there may be a loose or damaged spring at that end. For older vehicles, there may be a slight dent on one side of the car. If the dent is obvious, the leaf spring may need to be replaced. Move to each side of the car and check the binding of the link spring that may be located in front of or behind the leaf spring. Generally, when the vehicle is under its own weight, the link should be vertical. Any obvious forward or backward deflection means that the leaf spring is loose. Also compare the deflection of the binding on both sides of the car. They should be roughly the same. If this inspection shows that the rear leaf spring or springs are loose, further inspection at the repair shop is required to find out the cause.

 

Cleaning the leaf springs

Standard leaf springs are made up of several single leaf springs that are fixed together by clips and bolts. When the suspension is in motion, the leaf springs will wear when they rub against each other. To overcome this, some vehicles are equipped with single leaf springs with variable cross-section.

Dust particles between the leaves of the leaf spring will increase wear and rust. Therefore, the leaf springs should be kept very clean to extend their service life. Most leaf springs now do not require lubrication, as this may damage the wear-resistant material between any single leaves. As with most modern cars, the leaf springs are mainly distributed in the rear suspension to clean them. Remove the hub caps and wheel valve internals and loosen the wheel nuts. Use a jack to lift one side of the car off the ground and support the axle bracket under the chassis beam. Do the same for the other side of the car, so that the wheel on the ground is raised and the chassis can be supported on both sides. Try to lighten the vehicle to make the leaf springs natural and allow each leaf spring to separate individually, making it easier to clean.

 

If the leaf springs are full of dirt and grease, cleaning is a more troublesome task. At this time, you need to wipe them with a large amount of newspaper or plastic sheeting. If necessary, spray them with a special degreasing liquid or use a brush. Then wipe the leaf springs dry with a degreasing rag. If there is only some dry dirt or rust on the leaf springs, you can use a wire brush to remove all traces. Carefully clean the upper and lower surfaces and around both sides of the leaf springs and all the clips that are used to connect the single leaf springs together. After that, wipe them clean with a rag. After cleaning the leaf springs, lightly lubricate them with silicone lubricant and replace both wheels and wheel nuts. Lower the car to the ground and tighten the wheel nuts thoroughly.

 

Check the leaf springs and accessories

When cleaning the leaf springs, check if one of the leaf springs is flatter than the other. In this case, the car may be significantly tilted to one side. This will indicate that you also need to check the chassis height and check the edges of the leaf springs to see if there are any cracks. Cracks found in leaf springs cannot be repaired by welding and must be replaced with new leaf springs or complete leaf springs as soon as possible by a garage.

Check the lower surface of the leaf where the shorter leaf faces the end of the other leaf above. The tip of the shorter leaf may tilt into the surface of the leaf above, forming a slight depression. The leaves then bind as they move towards each other. Slight dimples are acceptable, but if a single dimple is more than 3mm, the leaf spring needs to be replaced. Check the condition of the shackle pins passing through the rubber bushings to make sure they are not bent or badly corroded. If so, the problem may be difficult to correct and can only be replaced by a garage.

 

Make sure the nuts of the U-bolts that hold the leaf springs on the shaft are tightened. If the nuts are loose, the shaft will allow the leaf springs to deflect, which will cause steering and tire wear problems, and can also cause judder when the brakes are applied. The leaf spring center bolt head or dowel pin that holds the leaf spring in place on the mounting pad may also be damaged, in severe cases, the shaft will move freely backwards and may break away from the leaf spring. Multiple leaf springs have two or more outward-facing clevises that hold the main single leaf spring in alignment with each other and may be connected by rivets or bolts. Check the condition and security of each clip. If you find any loose or broken, replace them immediately. Otherwise, the spring load will not be evenly distributed during the full suspension travel on uneven ground, which may cause the main leaf to break under pressure. In some cases, the short leaf of the leaf spring is not held in place by the leaf spring clip, but by the U-bolt to keep it in place with the rest of the leaf spring. If the U-bolt becomes loose, the short leaf spring may move laterally. In this case, tap it back into place with a soft hammer and tighten the U-bolt nut. With the parking brake tightened while going up a slope to stop the front wheels from rolling back, go to the rear of the car and check the rubber bushings at each end of the spring eye. Get out of the car and wipe the area around the bushings. Clean the bushings as much as the spring restraints will allow. Inspect each bushing for signs of wear or deformation caused by the long-term load on the car. Check whether the rubber has rotted, cracked or contaminated by oil. If the bushing is damaged, it must be replaced.

 

Check for looseness and rust

Remove the weight of the car from the suspension and check if the leaf spring is moving laterally. Remove the bearing seats for the front wheels of the car. Lift the rear of the car with a jack, supporting each side with the axle wheel stands of the chassis section, not the axle. Hold the spring firmly and try to twist it from each end. It should not move. Try to move the bushing from one end to the other to further check its stability. If the rubber bushing is secure, the leaf spring will not move laterally. If it does, the bushing needs to be replaced.

Use a wire brush to clean dirt from the floor near the leaf spring mounts and the shackle bolts. Check the tightness of each bolt and nut and tighten any loose bolts and nuts.

 

Take this opportunity to also look for signs of corrosion on other parts of the chassis. Corrosion can be detected by probing suspicious areas with a screwdriver or tapping them with a hammer. If you find severe rust in the assembly area, you will need to take the vehicle to a garage for repair. Do not use the vehicle until the problem is repaired. If it is just surface rust, clean the surface rust with a steel brush and then spray the surface with a professional rust inhibitor.