Pressure gauges
are the best way to diagnose a failed proportioning valve. There will be a gage installed into the front and rear hydraulic circuits. Start the vehicle, and apply the brake pedal with heavy pedal pressure to duplicate a panic braking situation. The front and rear pressures should be different.
How do I know if my combination valve is bad?
Since the proportioning valve decreases the pressure sent to the rear brakes, the main symptom the valve is going bad is
the rear wheels locking up when the brakes are applied
. Furthermore, the wheels will lock up more easily on wet surfaces. The rear brakes may feel touchy when applied even gently.
How do you reset a brake proportion valve?
- Locate the brake proportioning valve near the rear brake line. It will have one or two buttons located on it. …
- Push the reset button located on the valve with your fingers, which will reset it so the valve is working properly again. Inspect the brake pressure.
What causes a brake proportioning valve to fail?
For instance, if a
truck’s cargo area is heavily loaded, its rear end will typically drop
. This will cause the lever on the proportioning valve to work harder by supplying greater hydraulic pressure to the rear brakes compared to when the vehicle is lightly loaded.
How do you fix a stuck proportioning valve?
Place a
flare nut wrench
on the rear cap nut to the rear brake line. Instruct your assistant to hold the brake firmly, while you open the cap nut with the wrench. If the brake pedal does not move downward, have your assistant stomp on the brake pedal with medium to hard pressure, and hold it down firmly.
How do you adjust a load sensing proportioning valve?
Use light pedal pressure, and as an extra precau- tion,
move the lever to Position 7 (lever-type)
, or rotate adjusting knob in a clockwise direction (screw-type), to reduce internal pressure. The proportioning valve can be used to reduce brake line pressure, but will not increase it.
Can you bypass a brake proportioning valve?
The
valve will only work as designed if
the rest of the suspension retains the original specifications – if your car is significantly lowered or the suspension stiffened up, you might as well bypass the proportioning valve.
Will a bad proportioning valve cause a hard brake pedal?
Because the brake fluid can’t be compressed, the
pedal becomes rock hard
. … You still can generate moderate pressure on the “good” side of the valve therefore allowing the car to be driven in a limp home scenario.
What are the signs of a bad master cylinder?
- No Brakes. The most obvious symptom of a bad master cylinder is brakes that don’t work at all. …
- Poor Braking. Since usually only the brakes at the front or back will go out at a time, you will likely notice your car doesn’t stop as well as it should. …
- Inconsistent Brakes. …
- Leaks.
Do you need a brake proportioning valve?
A Proportioning valve is
required on vehicles that have disc brakes on the front wheels and drum brakes on the rear wheels
. … Having the rear brakes engage first provides the control and stability needed to stop your vehicle safety. The proportioning valve reduces the pressure to the rear brakes.
Where is the brake proportioning valve located?
The proportioning valve part of the combination valve is located in
the rear brake portion of the valve
. This part of the valve probably causes the most confusion within a combination valve and is probably the most misunderstood part of a brake system.
How do you replace a proportioning valve?
The average cost for brake proportioning valve replacement is
between $317 and $346
. Labor costs are estimated between $110 and $139 while parts are priced at $207.
How do you use a proportioning valve tool?
Designed for use with CPP proportioning valves, these tools
lock the valve in place and keep it from tripping when bleeding your brakes
. You simply remove the warning light switch (white plug) on the valve and screw in the tool while bleeding your brakes. After the process is finished replace the warning light switch.
How do you adjust a brake proportioning valve?
Use light pedal pressure, and as an extra precau- tion, move the lever to Position 7 (lever-type), or
rotate adjusting knob in a clockwise direction
(screw-type), to reduce internal pressure. The proportioning valve can be used to reduce brake line pressure, but will not increase it.
What does a brake load sensing valve do?
The load sensing valve (L.S.V.) serves
the purpose of automatically adapting the brake pressure and therefore the brake force according to the load of the vehicle
.
What does the combination valve do?
The valve
restricts how much pressure is applied to the rear brakes
, without this feature the rear system would lock up and cause the car to go out of control. If the car is equipped with a disc and drum combination, then a metering valve is also needed to regulate how much pressure is applied to the front wheels.
