Wheel cylinder repair and service

The wheel cylinder and piston set up pushes the brake shoes into the drum to slow the wheel down. There is three types of drum brake set ups...

 Duplex

Servo

Simplex

The wheel cylinder that we took apart was from a simplex system. It has two pistons in the cylinder facing away from one another. When the fluid from the master cylinder enters the wheel cylinder the fluid pushes both pistons out with the same force unless one of the pistons are jammed or the brake fluid is leaking past the piston seals. If the seals are leaking they will need to be replaced. The wheel cylinder will need to be honed if it is corroded inside (surface rust) if the wheel cylinder is badly damaged it will need to be replaced. NB If the cylinder is made of aluminium it is not possible to hone it. If the cylinder is made from cast iron use kerosene or methylated spirits as a lubricant when honing it. We measured the inside of the cylinder and the diameter of the piston to make sure that the seals will seal properly. Once the cylinder has been honed the we cleaned it with brake cleaner and replaced the pistons after putting rubber grease on the seals to stop them from being damaged. We then replaced the dust seals.