Shock absorber oil leak is a known quality issue in some markets and replacement of leaking
absorber is a logical course of action when the defect is observed. However, during the
investigation part, it was found that approximately one third of returned shock absorbers showed no functional defects.
We are afraid that a good number of healthy shock absorbers are mistakenly replaced under
warranty due to the lack of clear judgment criteria on the oil leak. We assume that in some cases a trace of oil adhered to the shock absorber is recognized as oil leak. Needless to say, very small
amount of oil adhered to the shock absorber does not immediately suggest an oil leak. Rather, it
could be a normal phenomenon resulted from the nature of a shock absorber.
Misjudgment and subsequent inadequate replacement of shock absorbers will not only result in
unnecessary cost, but would distort defect statistics and give negative influence to
With this TSL, we would like to provide you more clearly criteria judgment of oil leak from shock
Phenomenon & cause: sealing structure of shock absorber
The sealing of shock absorber has three functions:
- To seal the shock absorber oil inside the cylinder.
- To prevent dust from entering into the inside structure.
- To lubricate piston rod by forming an oil film.
The lubricating function of the seal as shown in the above drawing. Lubricates the piston rod by its sliding motion. As a result of repetitive sliding of the piston rod, oil film scraped off the piston rod or condensed oil vapor may adhere to the surface of the shock absorber casing. This small amount of oil seen on the surface of piston rod maybe recognized as an oil leak caused by defective sealing. However, this phenomenon is not defect of the shock absorber. Please be careful though that a faulty seal would cause an oil leak that shown a similar appearance.
Guideline for judgement by visual inspection:
We have established a diagnostic flowchart along with a guideline to help perform shock absorber oil leak judgment. When inspecting shock absorber, follow the flowchart below and if there is a visible oil adhesion, determine the level of severity and act accordingly. — corresponding to level 1. — corresponding to levels 2 and 3.
Guideline for categorization of oil leak severity.
Note: Details of length for Judgment of oil leak level by each model, refer to the below table.
Detail of length for judgment
Measure the length for judgment referring to the below tables.