A metering valve controlling fluid flow from the master cylinder will cause the rear drum brakes to engage just before the front disc brakes. Instead of nose diving, this allows the car to settle evenly under braking.
What happens when a metering valve goes bad?
Metering Valve Cause:
1 – Valve stuck OPEN: If the valve is stuck open, the vehicle will have instant-on front brakes (See figure 48.1). The front brakes will apply instantly, while the rear brakes will have to “play catch up.” The long-term symptom of instant-on front brakes is premature front pad wear on all pads.
What does a metering valve do in the brake system?
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.
What is the symptom of a car with a failed metering valve?
Rear wheels lock up
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.
What is the difference between a metering valve and a proportioning valve?
The metering valve works with a front disc/rear drum setup to hold off pressure to the front brakes until pressure has been applied to the rear brakes. The proportion valve works in a panic situation to hold off rear brake pressure and prevent rear brake lock-up.
What do combination valves incorporate?
A combination valve is exactly what it sounds like – a valve that combines the function of multiple other valves. It’s a way to simplify and streamline unvented cylinder operation and to make maintenance and repairs easier. A combination valve usually includes four different types of valves.
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 are the signs of a bad brake booster?
9 Symptoms Of A Bad Brake Booster
Stiff Brake Pedal Action. A hard brake pedal is often a strong indicator of brake booster failure. Increased Braking Distance.High Brake Pedal Position. Hissing Noise. Compromised Engine Function. Warning Lights Come On. Fluid Leakage. Overheated Hydro-Booster.
Does the metering valve delays front brake action?
The metering valve delays the flow of brake fluid to the front calipers until the pressure in the system rises to a point where the wheel cylinder can overcome the tension of the brake shoe return springs. This prevents the front brakesfrom locking up during light brake applications.
What is a hydraulic metering valve?
Metering Valves. In an automotive hydraulic braking system, metering valve momentarily delays application of the front disk brakes until the rear drum brakes begin to act. Metering valves are multi-turn valves designed to regulate the flow of fluid.
Why are metering valves used on the above systems?
Hold-Off/Metering Valves are used in the front (disc) system of a disc/drum brake system. They provide a “hold off” function to allow the rear (drum) brakes to actuate first. This function is very important in making the system function in the correct sequence in a rear-wheel-drive car.
How do you reset a brake proportioning valve?
How to Reset a Brake Proportioning 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.
Does the metering valve control the rear brakes?
Definition & Description. 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.
What happens as brake fluid ages?
As brake fluid ages it can absorb small amounts of moisture from its surroundings, including the air; this is called hygroscopic. If brake fluid becomes too full of moisture, problems can arise when the fluid becomes hot under braking, with the moisture turning to vapour inside the brake lines.
What limits hydraulic pressure to the rear brakes?
Valves commonly found in hydraulic brake systems include: Proportioning, or pressure-balance valves. These restrict a percentage of hydraulic pressure to the rear brakes when system pressure reaches a preset high value.
