When a Mercedes’ return line leaks, the damage can often be done before the first signs become apparent. The reasons for this are simple: It takes a while for symptoms to fully develop and they don’t always announce themselves with a loud crash!
Fluid Pooling Beneath the Car
Look for fluid pooling at the bottom of the car on the path a low-pressure return hose would take. It may be some distance from the steering rack but will be on the same side as the leaking return hose.
Staining Along the Return Hose
Run your fingers along the return hose. A return line leak will leave oily marks or even dried staining whereas a high-pressure leak will typically create a wet spray. This fluid is cooled and of low pressure.
Reservoir Level Dropping Slowly
The Mercedes steering rack is a closed hydraulic system. This means that the fluid in the reservoir should remain at the same level. If the level of fluid in the reservoir is dropping and there are no signs of leakage then the problem is likely to be with the return line.
For Mercedes Steering Racks, see https://westernpowersteering.co.uk/vehicles/mercedes/.
Steering That Heavies Up With Use
Steering may feel light at first but become much harder to steer after 10-15 miles. This is due to fluid loss reducing hydraulic assistance, whereas a high-pressure leak would cause heavy steering straight away.
Burning Smell From Under the Bonnet
Power steering fluid droplets falling onto a hot exhaust component can give off a very pungent and sharp smell. Be aware that it can take a while for this smell to become apparent. It is most noticeable after longer journeys and not immediately after starting up.
Catching a return line leak before it causes any damage will mean a simple repair to replace the leaking component and ensure the rest of the steering rack is protected from potential damage caused by it running low on fluid.
