What Is a Hand Valve on a Truck?

Hand valves are used to control the flow of fluid through a pipe by turning them on and off manually. In this article, we will discuss hand valves’ functions, their locations, and their purpose. We will also discuss air brakes and their cooling and overheating issues.


What Are Hand Valves and How Do They Work? 

Hand valves work by controlling the flow of fluid through a pipe. When the valve is turned to the “on” position, fluid flows through the pipe, and when turned to “off,” it stops the flow. Hand valves are often used in trucks to control the flow of diesel fuel into the engine. They allow drivers to control the fuel entering the engine, making them an essential vehicle component.

Where Is the Trailer Hand Valve Located? 

The trailer hand valve is typically located on the steering column. Its primary function is to apply brakes only to the trailer. At the same time, the foot valve operates both the tractor and trailer brakes. The hand valve sets the initial braking pressure for the trailer during road tests and brake adjustments. When making an emergency stop, use both valves to apply maximum braking pressure. When descending long grades, use only the foot valve to allow engine compression to retard the vehicle’s speed.

The Purpose of the Trailer Hand Valve 

The trailer hand valve controls the airflow to the trailer brakes. When turned on, air flows into the trailer brakes, and when turned off, it stops the airflow. The hand valve is also used to set the initial braking pressure for the trailer during road tests and brake adjustments. Using both the hand and foot valves in emergency stops is crucial to apply maximum braking pressure.

What is a Hand Brake Valve? 

A hand brake valve is a device that controls the airflow to the brakes. It is usually located on the steering column or dash and is used to apply brakes only when necessary. The hand brake valve is essential because it allows the driver to manually control the brake’s pressure.

Air Brakes Cooling and Overheating Issues 

Air brakes cool slowly because they push against the brake pads with compressed air. It can take up to an hour for the brakes to cool down completely, making it essential to use them carefully and avoid overheating. Overheating causes the air to expand, breaking the seals on the brake pads, leading to a loss of pressure and the brakes not working correctly. If the brakes overheat, it is essential to pull over and let them cool down.

How to Know If Your Air Brakes Are Working 

You can tell if your air brakes are working correctly by the hissing sound they make when the air brake system is turned on. This sound is the air pressure equalizing in the system. If you do not hear this sound or the brakes feel spongy, have a mechanic check the air brake system.

When to Use Air Brakes 

Air brakes should be used when descending a long grade to control the vehicle’s speed and prevent it from getting out of control. They should also be used in emergency stops to provide extra stopping power and to avoid skidding.


Hand valves and air brakes are essential components of any truck. Hand valves give the driver complete control over the vehicle’s brakes, and air brakes provide extra stopping power when necessary. It is essential to use them carefully and avoid overheating to ensure they work correctly. If you need help with how to use either of these devices, seek guidance from a professional.

About the author, Laurence Perkins

Laurence Perkins is the passionate car enthusiast behind the blog My Auto Machine. With over a decade of experience in the automotive industry, Perkins has knowledge and experience with a wide range of car makes and models. His particular interests lie in performance and modification, and his blog covers these topics in-depth. In addition to his own blog, Perkins is a respected voice in the automotive community and writes for various automotive publications. His insights and opinions on cars are highly sought-after.