Retarder Service, Repair & Overhaul

Voith repaired in our own workshop, Telma supplied as parts

On Voith (hydraulic) retarders everything from diagnosis to final testing stays in our own workshop — the labour is not subcontracted. On Telma (electromagnetic) we supply spare parts and give technical support in choosing them; we do not take on workshop labour such as coil rewinding or rotor balancing. We state this upfront so you do not send a vehicle out for nothing.

How is it done? Retarder repair

On Voith retarders, we begin with accurate diagnosis for performance loss, overheating, noise or oil leaks, then repair at component level — hydraulic pump, rotor, stator, sealing elements and electronic control unit. Whether a repair or a full overhaul is needed is decided by measurement after teardown.

When is it needed? Retarder overhaul

Complete overhaul for worn or damaged Voith retarder units: teardown, cleaning, wear measurement, part renewal, resealing, testing and performance restoration. A remanufactured unit is an economical, fast alternative to a new one.

How quickly? Retarder spare parts

We stock original and remanufactured Telma and Voith retarder spare parts: coils, rotors, discs, hydraulic pumps, gasket sets and electronic components — shipped same day from stock.

Compatibility with all heavy-vehicle makes and models

We provide technical support for retarder applications across all heavy-vehicle makes and models, including Mercedes, MAN, DAF, Scania, Volvo and Iveco. Our team helps with correct part selection and installation compatibility.

Retarder service in your city

Unit intake, parts delivery and how the unit reaches the workshop differ by city. Pick yours.

Retarder — frequently asked questions

What is a retarder and what does it do?

A retarder is an auxiliary braking system that slows a heavy vehicle without using the service brakes. It engages on long descents instead of constant use of the brake pedal, reducing wear on the brake linings and drums, preserving braking power and improving overall braking safety. On a long descent, if the service brakes alone carried the full load, the linings and drums would wear out quickly; the retarder takes on most of that load, keeping the service brakes ready for stopping and emergency braking. A retarder does not replace the service brake system: it works alongside it as a second, auxiliary slowing system. The service scope follows that same line: workshop repair and full overhaul are limited to Voith hydraulic retarders, while on Telma electromagnetic retarders we supply parts and support you in choosing them. We hold original and remanufactured stock for both systems, and in-stock items ship the same day.

What is the difference between Telma and Voith retarders?

Telma and Voith retarders work on different operating principles. In a Telma electromagnetic retarder, the magnetic field produced by the coils brakes the rotor; the system is dry. In a Voith hydraulic retarder, braking comes from turbulence in the oil flow; the system is tied into the cooling circuit. At KMQ Otomotiv the two systems fall under different scopes of service: on Voith hydraulic retarders we handle every stage ourselves in our own workshop, from diagnosis through to testing, repairing and fully overhauling at component level, from the electronic control unit and hydraulic pump to the rotor, stator and sealing elements. On Telma electromagnetic retarders we do not take on workshop labour such as coil rewinding or rotor balancing; instead we supply original and equivalent spare parts, including coils, rotors, discs, wiring harnesses, control levers and electronic control components, and give technical support in choosing the right one. In-stock parts for both brands ship the same day.

When is a retarder overhaul needed?

Performance loss, overheating, noise, oil leaks or reduced braking force may require an overhaul. Our technical team diagnoses whether a repair or a full overhaul is needed.

How quickly are retarder spare parts supplied?

In-stock Telma and Voith retarder parts ship the same day, with fast delivery across Türkiye through our 3-branch network.