Automotive Shock Absorbers Servicing Precautions


1. Handling of shock absorbers

Since the oil seal, piston rod, and other components of the shock absorbers are made with extreme precision, the following precautions must be taken when handling them:

Exposed portions of the piston rod must not be scratched to prevent leakage of shock absorber fluid. In addition, the piston rod should be kept free of paint and oil.

In order to prevent damage to the oil seal caused by interference with the piston valve, the rod and cylinder should not be rotated with the shock absorber extended completely. Particular caution is required in the case of gas-filled shock absorbers since the piston rod is constantly pushed up by the pressure of the gas.

2. Handling of gas-filled shock absorbers

Since pressure is constantly applied on the inside of gas-filled shock absorbers, the following precautions should be taken in addition to those described above:

Do not attempt to disassemble non-disassemblable shock absorbers (including all DuCarbon type shock absorbers as well as low-pressure gas-filled shock absorbers in which the ring nut is caulked).

When disposing of gas-filled shock absorbers, first evacuate the gas.

3. Evacuation of gas

(1) DuCarbon type Drill a 2 to 3 mm hole about 10 mm from the bottom of the removed shock absorber cylinder before discarding in order to release the pressurized gas. (This gas is harmless, colorless, and odorless, but metal chips may fly out during drilling, so work carefully. A good safety practice is to put a vinyl bag around the end to be drilled, fastening it in place with a strong rubber band.)

(2) Non-disassemblable MacPherson strut type In this type, in which the ring nut cannot be removed, lay the shock absorber assembly down horizontally and drill a 2 to 3 mm hole in the top of the absorber shell.

(3) Disassemblable MacPherson strut type

<1> Clamp the shock absorber in a vise.

<2> Slowly loosen the ring nut three or four turns until the gas begins to leak out. If the gas is allowed to escape too quickly, the absorber fluid may come out as well.

<3> Make sure that there is no gas remaining in the absorber before discarding. This can be determined by lifting the piston rod to the top of the cylinder and releasing it. If the piston falls back into the cylinder of its own weight, all of the gas has been exhausted.

4. Installation of cartridge type low-pressure gasfilled shock absorbers

Although the shock absorber is replaced only as an assembly in the case of many low-pressure gas-filled MacPherson strut shock absorbers, such assembly replacement is not necessary in some models. Instead, the piston rod with cylinder can be removed and a replacement cartridge installed. The following precautions must be taken in such cases:

Since the piston rod with cylinder and the cartridge have different shapes, cartridges should be used that come with their own ring nut.

When disposing of the cartridge, first evacuate the gas following the same procedure as in the case of the non-disassemblable MacPherson strut type.

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