Piper Aircraft Brake Bleeding

Hey all, Below I share with the aviation maintenance community how I prefer to bleed Piper PA-28/32 brakes. How do you guys bleed Piper brakes? Did my method work well for you guys?

Piper Aircraft Brake Bleeding

Methods I've Tried

Article: Piper Aircraft Brake Bleeding

#1 Old Fashion Oil Chan & Flex Hose

This method did not work for me. This is where you take an old school oil can, attach a short length of flexible hose. Then attach the flexible hose to the brake housing (located at the aircraft wheel).

#2 Pressure Pot Home Made

This method includes a pump up weed sprayer, a few barb fittings, and clear tubing. These items can be found at most hardware stores. Make sure to get the tube ID so it fits snug on the brake bleeder valve. I’ve gotten this method to work, but I had to go back in the cockpit and open up fittings near the brake actuator lines to release air bubbles. 

#3 Pressure Pot ATS Tool

This method is similar to method # 2 above except the tools is designed for the purpose of aircraft brake bleeding. The best part about this unit is the fitting used to hook to the bled valve on the brake. The fitting allows you to tighten the connection, and allows little to no leakage when bleeding. Ultimately this method didn’t work as well for bleeding piper brakes. The ATS Brake Bleeder 225 is still a great tool, and we use it for other aircraft. 

#4 Pressurizing The Brake Reservoir

This method requires screw on cap that fits the Piper brake reservoir. I don’t have a picture of the set-up I used. Essentially I took a screw on cap, drilled a hole in the middle, and epoxied a barb fitting to the cap. Then I attached a pressure pot with hose to the barb fitting. This method one of the better methods, but my favorite method is much simpler. See “Method I Use Now”

Method I Use Now

Article: Piper Aircraft Brake Bleeding

Using Aircraft Brakes With Bleed Hoses

This simple system is one I found to be the fastest and easiest way to bleed Piper aircraft brakes. The materials you’ll need are listed below.

Step 1: Attach clear tubing from each bleed valve (located at brake) to the brake reservoir located on the RH forward side of the firewall. Use painters tape to take the hose to the aircraft to keep in place.

Step 2: Top Off the brake reservoir with 5606 Hydraulic fluid. In addition, keep a quart or gallon of 5606 hydraulic fluid handy for keeping the reservoir full. 

Step 3: Open the bleeder valve one side (Left or Right) using a 1/4 wrench. I’ve had the most success doing one side at a time.

Step 4: Using the hand brake and brake pedal pump the fluid through the system. Only pump the brake in which you are working on. You should monitor the clear tube for fluid flow and bubbles. Alternate pumping the hand brake and foot brake. The hand brake seams to flow the most fluid, and I use it the most. Check the brake reservoir periodically and pump until you get no bubbles. 

Step 5: Close the brake valve with the 1/4 inch wrench. The repeat steps 1 through 4 on the other brake.

Step 6: When completed check the braking action by pedal/hand brake firmness. You can also have a second person push on the leading edge of the wing while another person holds the brake. Does the plane roll? If you fail on the first bleed attempt try again. If you can’t get it to bleed then I recommend rebuilding the hand and pedal brakes. Often times the seals are worn which prevents proper bleeding. 

Materials Needed

Trick I Learned Recently

Article: Piper Aircraft Brake Bleeding

Pre-Fill Brakes When Changing O-Rings

So recently I worked with another shop, and the owner of this shop showed me a trick that works pretty well. This applies to 0-ring replacement in the brake housing. This short cut prevents you from bleeding brakes after the o-ring change.

Step 1: Remove the brake housing and cap the aircraft line side to prevent fluid from draining.

Step 2: Replace o-ring as usual in brake housing. 

Step 3: Fill the piston cavity with 5606 prior to putting piston back in housing. You can push some fluid out by pressing the piston into the housing slightly (make sure bleed valve is closed)

Step 4: Place the pre-filled brake housing back on the aircraft and connect the aircraft side brake line. 

The key to making this trick work is to keep air out of the brake housing. When installing the pre-filled housing you can even connect the aircraft side brake hose. Then before tightening completely press the piston slightly to bleed/flush air from the housing at the airframe hose to brake housing connection. 

Michael Sawyer

Michael Sawyer

Michael is an A&P / IA with 15 years experience in aviation maintenance. This experience includes general aviation, corporate, and military. Michael has owned and operated aviation businesses since 2015. Currently he's helping others with aviation maintenance entrepreneurship. Email: msawyer@phalanxaviation.com

3 thoughts on “Piper Brake Bleeding”

  1. It sounds like you are describing a plane only having one brake pedal for each wheel brake and a hand brake, so an aircraft with only three brake cylinders. In my case the aircraft has five brake cylinders, so I would open the left bleed fitting and pump pilot’s left pedal, copilot’s left pedal, hand brake, repeat until firm, close the bleed fitting on the left brake, open the bleed on the right brake, and then pump right pilot’s pedal, right copilot’s pedal, hand brake, repeat until firm, and close the right brake bleed valve?

    1. Hey mike! Hope all is well your way. It has been a while since I’ve bled a piper with toe brakes on pilot & co-pilot sides. I believe their is a shuttle valve located between the brakes. When a user presses the brakes (pilot or co-pilot) this valve will isolate the pedals being pressed from the other set of pedals (So it acts as one set of pedals when being pressed). If it were me I would hook up tubing from brake to reservoir for one side. Then use the handbrake and bleed (watch for air bubbles to stop in the clear tubing, keep reservoir full). Once you stop seeing air bubbles close the bleed valve and check how the pedal for that side feels (both co-pilot and pilot positions). If its good repeat for the other side. If one of the positions isn’t good (pilot or co-pilot) then tap that brake to shuttle the shuttle valve to open that positions hydraulic circuit, and try bleeding again with the handbrake… I know if you can’t get them to bleed this way sometimes the seals in the hand pump or the brake actuators (in the cockpit) need replaced. Let us know how you do!

  2. Hi again. I’ve finished a first test flight after installing rebuild kits in the four main gear master cylinders and also the hand brake master cylinder in my 1974 Piper Archer. The four pedal master cylinders were fairly easy to access as the main body of the cylinders stayed attached to the airplane and only the brake pistons were removed for seal replacement. The hardest part of the rebuild operation was compressing the piston return spring to install a washer and the roll pin that held the return spring in place. Harbor Freight has replacement roll pins and a spring loaded punch to drive the roll pin into the piston rod.

    The hand master cylinder is a horse of a different color! The entire master cylinder assembly had to be removed from the airplane and pulled apart on the bench.

    I disassembled each master cylinder in a large cardboard box lined with a clean sheet and with a clean paper towel on the sheet. That kept everything clean and kept all the parts in one place during disassembly and reassembly. It also helped contain any part that tried to run away during the process!

    Once all the brake master cylinders were back on the airplane and reattached to the rudder pedals or the parking brake handle, along with the parking brake reattached to the input hose from the brake fluid reservoir and the output high pressure hose to the brake system, I latched the parking brake handle into it’s full aft position. Then I refilled the brake fluid reservoir and left a small funnel and a dip stick in the top of the reservoir and attached the bleed hose to the brake bleed fitting on the left brake and ran the other end to an empty quart brake fluid container I could see from the cockpit. The bottle was propped appropriately so it wouldn’t tip over. I opened the bleed valve 1 and 1/2 turns and then pumped about 20 strokes on the parking brake and watched the bubbles go by, got out and checked and refilled the reservoir, repeating until no more bubbles were coming from the left brake. Then I closed off the left bleed fitting and repeated the procedure on the right brake.

    Once on each side made all 5 brake controls rock hard. I’ve never felt my brakes operate so well before!

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