Citroën BX – That Sinking Brake Valve Feeling

3 min read

The BX 16Valve, being French and Citroën, is less than straight forward when it comes to suspension, steering and brakes. With the age of the vehicles, wear in the hydraulic components is an ever-growing problem. It’s finally time to solve one of my long-standing hydraulic issues, the brake valve.

Rear brakes and suspension

Brake Control Valve - Doseur
Citroën BX Brake Control Valve – Doseur

One of the biggest annoyances I have with the car is a sinking feeling in the rear end under braking. In normal circumstances, the high-pressure supply to the rear of the car drives both the suspension and the brakes. Once the rear suspension has risen, little fluid required to keep the very light rear end off the tarmac. This leaves more than enough pressure for the rear brake discs. Unfortunately, on my car, holding the brake reduces the pressure in the rear to the point the suspension sinks.

Citroën BX brake valve seals

Brake Control Valve Schematic - Citroen XB 453-4
Brake Control Valve Schematic – Citroen XB 453-4

The sinking is caused by worn seals in the Citroen BX brake valve. As can be seen in the diagram above, there are quite a few seals that can wear. The internal movement of the valves is only small, but with a lot of fluid passing through and many thousands of brake applications, wear is inevitable.

Refurbishing a brake control valve

Brake Valve Stripped Down and Seals Removed
Brake Valve Stripped Down and Seals Removed

I won’t cover refurbishing the brake valve here are there are great websites already coving it such as the Tramontana website. Being 30 years since the BX first hit UK roads, repair parts such as seals are becoming a struggle to find. While there are some dedicated Citroën Specialists, such as Chevronics, starting to remanufacture parts, some are just not available.

Finding Seals is getting harder
Finding Seals is getting harder

Fortunately, my local Citroën dealer was able to help me source the most critical parts and the valve was rebuilt. While I’ve had the refurbished valve on the car for over a year now it’s done little mileage. The hydraulic system has only recently been refurbished with new LHM and full re-piping.

And the result of overhauling the valve

The difference is fantastic. The rear suspension was sinking almost immediately on turning off the engine, it’s now staying up for hours. More importantly the brake pedal, typically while waiting at lights, the rear end is no longer slowly sinking. Very much a problem solved and it has improved my enjoyment of the car!


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