The main purpose of accumulators is to guarantee the right pressure in the system at all times, even when the engine its turn off the brakes can be push up to 50 times without losing any pressure in the whole hydraulic system.

The pressure comes from the lower part of the accumulator which is an sphere divided internally by a diaphragm. Nitrogen pressurised at about 70 kg/sq.cm is present isolated at the bottom by the diaphragm. When the engine of the vehicle is on, it activates the pumps which pump the fluid until it reaches 175 kg/sq.cm, at this pressure the return valve opens, sending fluid back to the reservoir. The normal pressure for the whole system is around 168 kg/sq.cm. Once the engine is off, the pressure inside the accumulator will allow for the proper functioning of the brakes up to 50 times.

A pressure sensor mounted on each accumulator warns the driver if the pressure in the spheres were too low. Warning lights in the facia panel are connected to this sensors. Cars that haven’t been turn on for a long time tend to lose pressure, the warning lights will be on immediately as you turn the keys to the first position. Once the engine is running the lights should immediately go off. If the warning lights go on right after turning off the vehicle then there might be a leak on one or both accumulators. Always discharged completely the accumulators before changing them by either pushing the brake pedal 50 times with the engine off or by bleeding the system.


  • The accumulator for chassis 01001 - 26700 is RH2343 which you can find clicking here.
  • The accumulator for chassis 30000 - 42000 is RH2390 which you can find clicking here.
  • The accumulator for chassis 50000 and forward (mineral oil) is CD6000GMF which you can find here.

All designs provided by Rob Wilde.