Parking Brake Valve Leaking- Quick Fix Guide

Let us guess, you, too, are having issues with your RV’s parking brake valve? Well, you’re in the right place because we are here to help you fix it!

Fixing your malfunctioning parking brake valve isn’t complicated; you can do it yourself.

First, it is essential to understand why your parking brake valve is leaking? Once you know the cause, you can learn how to fix it. There are more than one cause of leaking RV parking brake valve. But don’t worry, continue reading to find out what they are and the solutions! 

How to Spot a Leaking Parking Brake Valve?

Before we dive into this article, we must know how to spot a leaking parking brake valve. The first step is surely knowing that the issue with your RV is a leaking parking brake valve.

Let’s take a look at some common causes of leaking parking brake valves:

  • Whistling noise from the parking brake 
  • Fall in air pressure gauge 
  • Bouncing or moving RV 
  • Air release 

What are the Causes for Leaking Parking Brake Valves?

A leaking parking brake valve is a problem that shouldn’t be overlooked. Understanding the cause and acting on it as soon as possible is crucial.

As we mentioned earlier, there is more than one cause of a leaking parking brake valve. We’ve enlisted the causes down below!

Brake Chamber Leaking

One cause of a leaking parking brake valve is a leaking brake chamber. This is one of the most common reasons for a dysfunctional parking brake valve.

Your first instinct should be to connect and disconnect the brake lines. If this hasn’t worked, you will likely have to get a new diaphragm for the brake chamber.

When the diaphragm is torn or cracked, there is a leakage of air from the parking valve.

As the diaphragm’s air holding capacity is compromised, it results in a fall in the air pressure gauge.

Exhaust Port Leaking

The parking brake valve comes with an inbuilt exhaust port. A defect in the exhaust port may also affect the air holding capacity of the valve. Exhaust ports have multiple delivery lines which connect to other brake valves.

A leaking exhaust port may result from one of these lines malfunctioning. To find out which one, you can connect and disconnect all the lines one by one.

Once you disconnect a malfunctioning line, you will hear a rush of air coming from it. That’s when you know it is a bad line.

In case the air sounds are absent from all of these lines, it is most likely that the exhaust port itself is compromised.

Incorrectly Plumbed Relay Valve

The final cause of a leaking parking brake valve could be because of your relay valve. If your relay valve has been plumbed inaccurately, the parking brake valve is bound to leak air.

Relay valves have multiple ports in the parking brake valve. For instance, a line from the dash valve could have been plumbed incorrectly into the parking valve’s supply circuit.

One way you can try is by disconnecting the line that has the least diameter from the brake valve.

The yellow-colored ones generally have the smallest diameter from the brake valve.

If you notice air gushing out, you can confirm that the relay valve has been improperly fixed. 

Leaking RV Parking Brake Valve: Solutions!

Read further to learn how to solve these issues!

What if my RV’s brake chamber is leaking?

A leaking brake chamber is associated with a torn or cracked diaphragm. It is essential to cage the spring before you start fixing the diaphragm.

Please ensure that the spring is completed and inserted. Next, turn it at an angle of 90 degrees. This way, there is an engagement of the bolts in the parking brake.

Now, carefully take out the clamp that holds the diaphragm. This could be a safety hazard when performed improperly. Once you’ve safely removed the clamp, remove the damaged diaphragm. 

Now, all you need to do is install the new diaphragm! Simply pull the slack and adjust behind. You can then use a vise grip to hold the spring to fix the new diaphragm easily.

After you’ve finished fixing the new diaphragm in the brake chamber, it is time to reposition the clamp and reassemble all the parts. Please don’t forget to remove the cage bolt and place the rubber plug back.

Here are some great options to entirely replace your brake chamber! 

  • 30×30, 3030, 30 30 Air Brake Chamber – NO CLEVIS – Sealed, 30/30 New
  • 30/30 Piggy Back Air Brake Chamber Kit by National Drivetrain
  • TORQUE Type 30/30 Air Brake Chamber Welded Clevis 2.5″ Stroke (TR3030C-WC)

What if there is a leak in my RV’s exhaust port?

If your exhaust port is leaking, it could be because of the delivery lines it connects to or the port itself.

By connecting and disconnecting each line, you can figure out which one is damaged.

If you find a defective line that leaks air, you can simply replace it with a new line. You don’t need to worry much about this as it is not a difficult or time-consuming chore.

Have you checked all the lines? Didn’t find a faulty one? This indicates that the problem is associated with your exhaust port itself.

If your exhaust port is damaged, it calls for a new one. You must replace the entire unit and connect it to the parking brake valve.

You must also adjust and connect all the delivery lines to the valve again. It is crucial to pay extra attention while doing this as you have to ensure that all the lines have been correctly placed.

If you find this task too complicated or tiresome, you can always hire a professional to replace the port.

What if my relay valve is inaccurately plumbed?

Sometimes, relay valves can be plumbed inaccurately. This is one of the contributory causes of a leaking parking brake valve.

If the relay valve has been misplaced, all you need to do is place it in the correct position. This isn’t always a repair that everyone can pull off.

So, if you need to hire a mechanic, you can always call one! Once you’ve accurately paced the relay valve, inspect for more potential leaks. 

Frequently Asked Questions (FAQs)

What does the crack pressure on my relay valve mean?

The relay valve has something called a crack pressure. The crack pressure is the pressure of air needed from the foot valve at the input. This air pressure input is required for the relay valve to send pressure to the brake.

What does a slack adjuster do?

The slack adjuster is responsible for transferring the braking torque to the S-cam. It adjusts the space between the brake drum and the lining of the brake.

What is the 30/30 brake chamber in my RV?

A type of brake chamber that measures an area of 30 square inches in each chamber is called a 30/30 brake chamber. The parking valves on the cab dash release air into these chambers.


A leaking parking brake valve is enough to set back your day on the RV. It is an issue that requires significant attention and an immediate fix.

Otherwise, it could worsen the condition of the braking system. This could result in your RV’s braking system failing entirely.

So, please get the leak fixed as soon as you spot it.

You can fix the leak in the parking brake valve by troubleshooting some its parts.

However, if the problem is still not fixed, it is best to call the mechanic to help. 

We hope you found our article informative. Thanks for reading!