The brake force regulator is replaced if the piston is seized or if brake fluid leaks.
On a vehicle without ABS, fluid is supplied to the rear brakes through a pressure regulator located on the underbody, between the rear suspension beam and the spare tire mount.
As the load on the rear axle increases, the regulator linkage, connected to the rear suspension beam, is loaded, transmitting force through the pressure lever to the stud and then to the two regulator pistons.
When the brake pedal is pressed, fluid pressure tends to push the pistons outward from the regulator housing, which is resisted (via the spring) by the force from the regulator linkage.
When the system reaches equilibrium, the valve located in the regulator shuts off the fluid supply to the wheel cylinders of the rear brake mechanisms, preventing further increase in braking force on the rear axle and preventing the rear wheels from locking ahead of the front wheels.
You will need a special 11 mm wrench for brake lines, a 13 mm wrench, and a flat-blade screwdriver.
Unscrew the nuts securing the four lines to the regulator and move the lines to the side.
Plug the holes in the regulator housing 1 and the lines in any way possible to prevent brake fluid from leaking.
Using a screwdriver, unfasten the clamp on the load rod of the regulator and remove the load rod, removing its ends from the holes in the bracket on the rear suspension beam and in the pressure regulator lever in the rear brake hydraulic system.
Remove the two bolts securing the regulator to the body and remove the regulator.
Install the brake force regulator in the rear brake hydraulic system in the order Reverse the removal procedure.
Fill the brake fluid and bleed the system (see "Replacing the Renault Logan Brake Fluid").
Pre-test the regulator's efficiency by braking sharply on a dry, uniform surface.
The rear wheels should lock significantly behind the front wheels.
If the rear wheels lock before the front wheels (or simultaneously with them) or the brake marks from the rear wheels are of different lengths, the pressure regulator needs to be adjusted.
The rear brake hydraulic system's force is adjusted using the adjusting nut on the regulator lever.
However, pressure in the hydraulic circuits must be monitored using special tools, which is only possible in a service center.
Furthermore, the brake force regulator in the rear brake system is a device that directly impacts driving safety.
Adjusting it by eye can have serious consequences. Therefore, if the regulator is not working properly, be sure to contact a service center.