Assessing Shock Absorbers for Leaks

Repairers and automotive spare parts distributors are sometimes asked to inspect, assess and replace shock absorbers that are mistakenly diagnosed as leaking. Misdiagnosis invariably results in unnecessarily taking productive vehicles off the road thereby inconveniencing customers, drivers and fleet operators with delays and unwarranted expenses as spare parts are ordered, delivered, and fitted. The environmental impact of unnecessarily replacing functioning components is also significant with waste going to landfill, an environmental no-no, and recycling of components although responsible, requiring time, freight, energy, and someone to pay for the process and storage of materials.

Misdiagnosed leaks primarily fall into two categories.

  1. Assembly Oil
  2. Misting/sweating
  1. Assembly Oil

Several different lubricants are used in the construction of shock absorbers. KONI uses assembly oils which are yellow or black in colour, sometimes appearing brown on the damper. This assembly oil is easily distinguished from the hydraulic damping fluid which is used within the shock absorber.

Blue hydraulic fluid.
KONI passenger car dampers (Classic, STR.T, Special Active and Sport).
KONI 4WD & SUV dampers (Heavy Track, Special Active and a few Sport).
KONI commercial vehicle cab dampers.

Red hydraulic fluid.
KONI 4WD (Raid)
KONI commercial bus, truck and trailer applications.

New shock absorbers may have a slightly moist rod, seal and/or body. Excessive assembly oil which will not be detrimental to the damper itself may even “run” and stain the cardboard carton the damper is supplied in. If excess oil is evident, wipe the damper clean and proceed with the installation. The damper is fit for service. If a brand new damper has bright red or bright blue hydraulic fluid droplets, the damper should not be fitted to the vehicle. The fitter needs to contact Toperformance Products for further instruction.

  1. Misting/Sweating

Any mechanical moving component requires lubrication for a long service life. A shock absorber is no different. It is necessary for the oil seal the rod passes through to remain lubricated.

As a vehicle travels over uneven terrain, the continuous inward and outward movement of the shock absorber piston rod will invariably cause oil to “sweat” from the top seal and drift through the surrounding air. We refer to this condition as “misting” and it will be evident from the moist stain on the outer body to which dust and other contaminants will adhere. Usually there are no droplets of oil clinging to the shock absorber. There is no need to be concerned by this condition as it does not indicate the oil seal has failed. It can be surprising how just a small amount of oil can leave a large stain, however the relatively small volume of hydraulic fluid emitted through misting has no effect on the operation of the shock absorber. In fact, because KONI does not compromise on the quality and volume of hydraulic fluid used in their shock absorbers, a KONI damper can lose up to 30% of its total oil volume before its operation is negatively impacted. Damping forces are not reduced through misting and a KONI shock can remain in service with this condition for many years and many kilometres. We do however recommend that any shock absorber be cleaned to remove any build up of dirt during regular maintenance.

Where bright blue or bright red droplets of hydraulic fluid are evident on the surface of the shock absorber body or dripping from its base, the seal may have failed, and the damper may need to be replaced or repaired (if it is of a design that can be serviced). Please contact Toperformance Products to discuss potential repair or replacement options.

… it’s probably not leaking!

KONI produces large volumes of shock absorbers for general automotive, off road/SUV, bus, truck, commercial trailer, racing, military, railway, and civil engineering applications. KONI shock absorbers are used in extreme environments all around the world and yet KONI piston rod seal failures are extremely rare. Regrettably, sometimes totally serviceable KONI shock absorbers are removed from vehicles and sent to Toperformance Products for warranty assessment only to be found to be functioning normally and not leaking hydraulic fluid.

The high quality range of KONI shock absorber products imported and distributed in Australia by Toperformance Products are covered by the warranty as described here.