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 test a metering valve?
The metering valve is holding off the pressure until the rear drum brakes have applied. It’s best to use a pressure kit to test this delay and measure actual fluid pressures. Connect a pressure gauge to the inlet and another to one of the outlet ports. Compare the results.
What does a brake metering valve do?
A brake metering valve is used to Balance the Braking Forces . It is only found on vehicles with front disc and rear drum brakes. The metering valve holds back fluid to the front brakes until enough pressure is created to overcome the return springs inside the rear drums. It is also known as a “metering block.”
What is the difference in a proportioning valve and a metering valve?
The brake metering valve, similar to the proportioning valve, is used to achieve balanced braking . ... On the front disc and rear drum brake systems, the metering valve delays the front calipers just long enough to overcome the rear brake springs and linkage.
How do I know if my metering valve is bad?
First, you might notice your car is taking a nose dive when you suddenly apply the brakes. Then your car may not stop fast enough. If your rear wheels lock up easily , especially when you drive on wet surfaces, it is a good sign your proportioning valve is going bad.
Why are metering valves not used on all vehicles?
why are residual check valves not used in most vehicles? Many vehicle’s today use cup expanders in the wheel cylinders that keep an air tight seal. This prevents air contamination , eliminating the need for residual check valves.
What causes mushy brakes?
Air in the brake lines is one of the most common causes of spongy brakes. Braking systems rely on evenly distributed hydraulic pressure to bring vehicles to a halt. Air in any of these lines can throw off this balance of pressure. ... Air in the brake lines could be due to a leak or low brake fluid.
How do you unstick a brake proportioning valve?
Tap the proportioning valve with a tack hammer several times lightly — sometimes this frees up a corroded bore and piston spool inside the valve. Wiggle the brake light warning switch wire on the top of the proportioning valve, making sure it has a tight, clean connection.
Where is the metering valve located?
Metering valves will usually be found inline leading to the disc brakes . Just as the name implies, residual pressure valves will retain a small amount of pressure in the lines, usually between 2-10 lb. designations.
What is a metering ball valve?
SM Series Metering Ball Valves
Chemline SM Series Metering Ball Valve is designed for fine linear flow control of chemicals or clean fluids . The ball is solid with graduated V-groove cut on the outside surface. ... With a positioning electric actuator, this becomes an inexpensive control valve.
Do I need a metering valve?
For your disc / drum brake system, a metering valve is essential for proper balance . A metering valve will control fluid flow from the master cylinder causing the rear drum brakes to engage just before the front disc brakes. This allows the car to settle evenly under braking instead of nose diving.
Do you need a proportioning valve with drum brakes?
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.
How do you test a brake proportioning valve?
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 does a proportioning valve equalize braking action?
The proportioning valve reduces the pressure to the rear brakes . If equal braking force were applied to all four wheels during a stop, the rear wheels would lock-up before the front wheels. The proportioning valve only lets a portion of the amount of pressure to the rear wheels thus preventing rear wheel lock-up.
What is a quick take up master cylinder?
This master cylinder contains a quick take up valve and a large primary chamber to provide the extra volume of fluid to compensate for the extra distance. The fluid bypasses the seal and provides the volume of fluid necessary during the initial brake application.
