Assessing Shock Absorbers for Leaks

assessing shock absorbers for leaks

Repairers and spare parts distributors are sometimes asked to tackle the inspection task of assessing shock absorbers for leaks. On occasion, it is possible to assess and replace shock absorbers that are mistakenly diagnosed as leaking.

Misdiagnosis invariably results in unnecessary down time, inconveniencing customers, drivers and fleet operators with delays and unwarranted expenses as spare parts are ordered, delivered, and fitted. Not to mention the environmental impact of discarding perfectly working dampers or the added cost of recycling.

assessing shock absorbers for leaks

Misdiagnosed leaks primarily fall into two categories: Assembly Oil and 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 body of the shock absorber. This assembly oil is easily distinguished from the hydraulic damping fluid which is used within the shock absorber. 

Below is a guide to which shock absorber contains which coloured fluid.

Blue hydraulic fluid.

KONI passenger car shock absorbers (Classic, STR.T, Special Active and Sport). 

KONI 4WD & SUV shock absorbers (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.

The piston rod, seal and/or body of new dampers may have a coating of assembly oil. 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. 

In the unlikely event bright red or bright blue hydraulic fluid droplets are found on the outside of a new shock absorber, do not fit the shock absorber to the vehicle. Instead contact Toperformance Products for further instruction.

assessing shock absorbers for leaks

2. 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 piston 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, through the top seal, will invariably cause oil to ‘sweat’ from the seal and drift through the surrounding air. This condition is known as ‘misting’.

Misting will be evident by the damp stain on the outer body of the shock absorber 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. 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 shock absorber can lose up to 30 per cent of its total oil volume before its operation is negatively impacted. Damping forces are not reduced through misting and a KONI shock absorber 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.

assessing shock absorbers for leaks

… it’s probably not leaking!

KONI produces large volumes of shock absorbers for general automotive, 4WD/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. Unfortunately, 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.

To save time and money please refer relevant service personnel to this article if they suspect a damper may be leaking. If you require any further assistance do not hesitate to contact Toperformance Products, Australian distributor of KONI shock absorbers.

Article submitted by Dean Marchetti, Toperformance Products, Australian Distributor of KONI Shock Absorbers. visit the website at 

assessing shock absorbers for leaks