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The R107‘s power steering is a recirculating-ball steering box fed by a belt-driven pump. It is durable, but the fluid is often never changed, and seals start to leak with age.
Fluid type
Mercedes specifies its own power steering fluid for these cars. Use the fluid listed in your owner’s manual or the factory fluid specs; do not use brake fluid or random universal fluids. Mixing incompatible fluids can damage seals.
The filter in the reservoir
The reservoir has a small filter inside, under the lid. It is often forgotten. Replace it when you change the fluid. A clogged filter can cause noise and heavy steering.
How to flush
- Remove as much fluid as possible from the reservoir with a suction tool.
- Replace the filter.
- Refill with fresh fluid.
- Start the engine and turn the steering lock to lock a few times.
- Repeat the suction and refill cycle several times until the fluid looks clean.
A full flush by disconnecting the return line is more thorough but messier.
Common leaks
- High-pressure hose from the pump to the box: crimps and rubber sections weep.
- Return hose and its clamps.
- Pump shaft seal.
- Steering box input shaft seal and sector shaft seal.
Pump noise
A whine, especially at full lock, points to low fluid, a clogged filter, air in the system, or a worn pump. A squeal points to a loose belt; see belts.
Box leaks
Leaks from the steering box are usually at the seals. The box can be resealed or exchanged. Do not overtighten the box adjuster to cure play; see steering play.
Quick answers
- How often should I change the fluid? There is no strict interval on these cars; on a car with old, dark fluid, flush it.
- Can a power steering leak cause a fire? The fluid can burn if it drips on hot exhaust parts. Fix leaks.
- Is heavy steering always the pump? Not always. Check tire pressure, the steering coupler and the front end first.
- What color is Mercedes power steering fluid? It varies by type; use the fluid specified for your car rather than going by color.
- Can a stiff steering wheel be the coupler? Yes, a worn or dry steering coupler can make steering feel notchy.
- Do I need to bleed the system after a hose change? Turn the wheel lock to lock with the engine running and top up until no bubbles appear.
