Checking restrictor valves
To check the limit valves associated with the GTZ, on vehicles without anti-lock braking system, use two pressure gauges.
These valves limit the GTZ output pressure to the rear brakes when the brake master cylinder reaches a predetermined pressure. On vehicles with ABS, the hydraulic modulator assembly controls hydraulic pressure to the rear and front wheel cylinders.
When checking the brake restrictor valves, make sure that the pressure in the hydraulic pipes is measured simultaneously for a pair of wheels located diagonally (e.g. front left and rear right).
To measure pressure, follow these steps.
1. Remove the bypass valve and install a pressure gauge on one of the rear brake cylinders.
2. Remove the bypass valve and install another gauge to the brake line of the diagonally opposite wheel.
3. Quickly depress the brake pedal several times to apply pressure. (The pressure read on the pressure gauge is not adjustable and is the actual hydraulic pressure of the brake system.)
4. Increase the pressure until the test values shown in the following restriction valve test table are reached.
|
Engine 1.5SOHC |
Reference value for gradient and cut-in pressure on the valve body |
Inlet pressure read from the pressure gauge on the front axle |
Outlet pressure read from the pressure gauge on the rear axle |
|
0,3/30 |
4 500 kPa |
3 450 + 200 kPa |
Attention: when the pressure rises above 10000 kPa, the pressure value read from the rear pressure gauge will be incorrect.
5. Remove pressure gauges from the brake circuit to be tested.
6. Reinstall bypass valves and tighten to 6 Nm.
7. Repeat the test on the remaining front and rear brake circuits.
8. Reinstall bypass valves and tighten to 6 Nm.