Schematic Air Parking Brake Valve Diagram (Bendix, Sealco)

There are different types of brakes for different vehicles. Air brakes are usually found in heavy-duty vehicles because they are better than brake pads. These air brakes work with compressed air which provides the pressure to press the piston and slow down the vehicle

The air brake system is made of a two-stage air compressor driven by the crankshaft or gearbox shaft. The air comes from the outside atmosphere, then compresses it and after that sends it to the air reservoir. That is just the first step in the air brake system.

To learn more about this braking system, just continue to read our article. It is filled with diagrams and information that will help you when your RV comes equipped with air brakes. However, you may need t be an air brake specialist to work on the system.

Air Parking Brake Valve Diagram

There will be different air brake system designs. But generally, they operate under the same principle. The above information is just part of how the air brake system works.

The rest of the story is that each wheel that is fitted with this system will also have a diaphragm. When you step on the brake, or apply the parking brake, compressed air is sent to the diaphragm and pushes it.

When that happens, the cam actuating lever is then moved into position and the brake is applied. Here is one generic air parking brake diagram:


The brake valve is on the green and orange line. But there are several valves to this system as you can see by looking at the diagram.

Bendix Parking Brake Valve Diagram

This company is well-known for its braking systems. It is a highly respected company that is constantly looking to improve their products. According to their website, their valves are supposed to be the product of the highest engineering standards possible at this time.

What this continual drive to improve their braking systems does is make the air brake and other braking systems more sophisticated while improving braking performance.


This is just one possible schematic and as you know different systems will be manufactured to meet different vehicle sizes as well as braking requirements. If you need a more specific diagram try contacting Bendix for your specific vehicle.

Air Brake Valve Diagram Kenworth

This company has been around for exactly 100 years. It is a very well-established name in trucking as well as other aspects of truck manufacturing including braking systems.

The company is also known for being the first in creative and innovative truck designs including the sleeper, using diesel engines and more upgrades. They have a long track record of producing great trucks that were equipped with excellent braking systems.

The following diagram is labeled as a Kenworth air parking brake system and it should give you a good idea of how the system works.


Sealco Park Brake Valve Diagram

This is another company that has been around for a very long time. Not as long as Kenworth but they have almost reached their 75th birthday. From its humble beginnings as a screw machine shop, this company developed into the largest supplier of air parking and other air brake valve manufacturing plant.

According to their website, they have valves in over 34 countries and millions of trucks everywhere. If you want more good news, this is a 100% American-owned manufacturing plant.

Everything they do is made in America. From design to assembly, all manufacturing steps are done in this country. Here is a diagram of one of their air parking brake valve systems:


Peterbilt 379 Parking Brake Valve Diagram

This company has been around since the start of the 2nd World War. It began in 1939 and it spent the war years building trucks for the military. In 1958, it was acquired by the PACCAR or Pacific Car and Foundry Company and the latter company has owned Peterbilt for roughly 60 years.

It was in 1986 when the company introduced the 379 truck and it become one of the most popular trucks for owner-operators to buy. This company is still looking to make top improvements to its trucks and components even after being in business for 84 years.

Here is one diagram for the 379 model air parking brake system:


Parking brake information

To set the air parking brakes, normally you would see a yellow diamond-shaped knob somewhere on your dash. RVs may have a different design depending on their model and manufacturer.

You pull this knob out and the parking brake is set. However, if this does not set the air parking brake, you have 2 manual options to use to get it set.

#1. Turn the ignition off and pump the brakes to release air into the system

#2. If your RV or truck comes with a dump switch, turn the ignition to the ‘on’ position. Then press the dump switch to lower the air pressure in the system.

To prevent the unintentional release of the parking brake, some air brake companies have developed a safety interlock connection. There are 6 sets of instructions to follow to release the parking brake.

We will only quote the first two and you can read the rest at this link.

Parking Brake Interlock Release

1. Depress the brake pedal.

2. Push the parking brake control valve in.

Parking Brake and Ignition Key Release

1. Turn the ignition key to the ON position.

2. Depress the brake pedal.

3. Push the parking brake control valve in.

Some additional words

These diagrams should get you on the right track for doing what you need to do with your parking air brake. If you are not qualified to work on air brakes, you should not touch the system.

If you do and a problem happens, the courts do not look favorably on you. The best thing to do is go to a trusted air brake technician and let them handle all your air parking brake issues.

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