3 Signs of a Bad Brake Booster Check Valve (& Replacement Cost)

The brake booster check valve may seem like a small part, but it can cause a lot of damage if it's bad. Here's how to tell your brake check valve is bad.

symptoms of a bad brake booster check valve

Your car’s braking system contains a vacuum brake booster that is responsible for creating pressure. When your vehicle suffers from a bad brake booster check valve, you could notice a variety of symptoms.

When you push the brake pedal, you want to know everything is working the way it should. To help you out, we will look at the problems a defective brake booster check valve can cause and discuss what’s required to fix it. Let’s take a quick look at the signs to look for first.

The most common symptom of a bad brake booster check valve is a stiff brake pedal. You may also notice issues like trouble braking or a check engine light on your dashboard.

Here’s a more detailed list of the most common symptoms of a bad brake booster check valve:

3 Bad Vacuum Brake Booster Check Valve Symptoms

1. Hard Brake Pedal

push brake pedal

Stepping on the pedal shouldn’t be difficult when everything is working as it should. If you push on the brake pedal and it is difficult to move, there could be a problem with the brake booster check valve.

Typically, when the check valve becomes worn out, it will not hold the vacuum pressure inside the brake booster. The brake pedal will become firmer, requiring much more pressure to depress it. The reason this occurs is because the master cylinder contains more pressure inside due to a faulty check valve that is meant to ensure regulation. 

2. Trouble Braking

If the vacuum brake booster check valve has a small leak, it may result in not enough vacuum pressure in the brake booster and this will make the brakes much less efficient and it will require much more force to stop the vehicle.

If it feels like the stopping distance of your car is much longer than usual it is definitely time to check your brake booster check valve.

If it feels like the brakes are getting much worse recently after acceleration it is definitely a sign of a bad brake booster check valve.

3. Check engine light

The brake booster check valve is using vacuum pressure from the air intake to create vacuum in the brake booster system. This air is usually measured by the MAF sensor and if the check valve is leaking it will result in a loss of measured air. This will cause the car to run lean or rich depending on the engine type.

When the car is running too lean or too rich this will result in a check engine light on your dashboard and a stored trouble code. You can use an OBD2 scanner to find any related air-fuel mixture trouble codes.

Brake Booster Check Valve Location

brake booster check valve location

Typically, the brake booster check valve is found on the brake booster. If you don’t see it there, it would be found in line with the vacuum hose. 

The vacuum booster is a dome-shaped component that’s mounted near the rear wall of the engine compartment. You should be able to find it on the driver’s side of the vehicle, running in line with your brake pedal. You can follow the vacuum hose running from the intake manifold on the engine to the vacuum booster. 

The Function of a Vacuum Brake Booster Check Valve

brake booster check valve

The brake booster contains multiple parts, but one important aspect is the check valve. It takes vacuum pressure from the air intake when the engine is idling and creating a vacuum pressure in the brake booster.

The check valve is a small part but vital to ensuring the proper link between the vacuum hose and brake booster. With a reliable check valve, the brakes can function as intended every time you stop on the pedal to stop. 

In general, the brake booster check valve should last the lifetime of the car. In fact, it doesn’t get inspected during a routine brake check and there is no maintenance to perform. With that said, the lack of attention means that when it breaks or fails, it isn’t noticed until symptoms occur. 

Brake Booster Check Valve Replacement Cost

The cost to replace a brake booster check valve is between $70 and $85. In general, the labor costs will be around $30 and $45, while the parts should cost about $40. 

If you have some mechanical knowledge, replacing the brake booster check valve isn’t a complicated process. You could easily do it yourself with the right tools and save a little money. You would need to remove a few clamps and the vacuum hose to get to the check valve. 

However, there might be some other services that need to be performed at the same time. For example, if air got into the lines because of the defect, the brakes will need to be bled.

Written by:

Magnus is the owner and main author of MechanicBase. He has been working as a mechanic for over 10 years, and the majority of them specialized in advanced diagnostics and troubleshooting. He has also been a motorsport (drifting) driver for over 5 years.