Bleeding brakes

They are all interconnected so there isn't a way from what I've seen or read anywhere. That's why it is such a beeahtch to bleed Piper brakes.

So even if I have a hose sticking through the fill port of the reservoir and into a container, there is a lot of room around the hose at the fill port. What prevents the hydraulic fluid from simply bypassing the hose and going for the least path of resistance to the fill port and overflow? Unless I fashion a cap with a hole in it to fit the opening OR I attach a hose to the little curved air tube on the cap I don't see how that would work. And even when I'm done, it seems I'd still have to suck out some of the hydraulic fluid to get it down to the required level.
 
I have no words of wisdom, only condolences. My Cherokee (69) had the hand, and toe brakes only on the pilots side. Had to replace/rebuild one of the toe cylinders due to the damn itty-bitty rod got slightly bent. My partner & I spent HOURS working a little bubble out. I'm convinced that little bubble moved 1/4" back and forth between 2 M.C.'s. It moves so little fluid that it just takes time. Stick with it......
 
Excerpt from Archer MM for illustrative purposes. Hopefully it makes sense. Start with the hand brake, the copilot side next and the pilot side last. Note the number of pumps mentioned.

U. BRAKE BLEEDING PROCEDURE (Gravity)

1. Attach a clean, clear plastic tube to right landing gear brake bleeder. Extend the free end of the tube to

a container partially filled with hydraulic fluid (MIL-H-5606). Check the end of tube is submerged in

fluid. Open bleeder 1 /2 to 1 turn.

2. Fill brake fluid reservoir, located on the firewall, with hydraulic fluid.

3. Check right hand toe brake pedal(s) in cockpit have been pulled full aft.

4. Pull hand brake handle and slowly pump master cylinder approximately 50 times or until hydraulic

fluid is observed passing through plastic tube at brake bleeder.

—NOTE—

Fluid level in reservoir must be maintained to prevent air from

entering system.



5. Pump right brake cylinder very slowly approximately 12 times. This will purge air from toe brake

cylinder system. Watch for any air forced through clear plastic tube during this operation. Verify air

has been forced from toe brake system.

6. Pump hand brake an additional 25 times or until no air is observed through clear plastic tube.

7. Tighten brake bleeder and remove plastic tube.

  1. Repeat steps 1 through 6 for left main landing gear.




V. BRAKE BLEEDING PROCEDURE (Pressure)

1. Place a clean, clear plastic tube on vent fitting on top of brake fluid reservoir. Extend the free end of

tube to a container partially filled with hydraulic fluid (MIL-H-5606). Verify tube end is submerged in

fluid.

2. Attach another clear plastic tube to right landing gear brake bleeder. Connect the free end of tube to

pressure source. Open bleeder 1 to 2 turns and pressure fill system with fluid.

3. With fluid continually flowing through system, SLOWLY and simultaneously actuate hand brake and

toe brake pedal, of side being bled, several times to purge air from cylinders. On dual brake installations,

actuate both pedals for brake being bled.

—NOTE—

By watching the fluid pass through the plastic hose fluid

r e s e rvoir and the bleeder fitting on gear being bled, check if

any air is left in system. If air bubbles are evident, filling of the

system must continue until all air is out of the system and a

steady flow of fluid is obtained If brake handle remains

s p o n g y, disconnect the bottom of toe brake cylinders (next to

pedal) and rotate cylinder horizontally or above horizontal and

use hand brake alone to purge air from system.

4. Close the open bleeder fitting to which the pressure hose is attached. Do not remove tube from fluid

reservoir until both brakes have been bled. Check brakes on the side being bled for proper pedal pressure.

Place cap on bleeder fitting.

—NOTE—

Remove any trapped air in the top of wheel brake unit by

applying pressure to the system with the brake hand lever and

slowly opening bleeder and releasing hand lever.

5. Repeat Steps 2 through 4 for left main landing gear.

6. Drain excess fluid from reservoir to fluid level with syringe.
 
JAWS said:
Excerpt from Archer MM for illustrative purposes. Hopefully it makes sense. Start with the hand brake, the copilot side next and the pilot side last. Note the number of pumps mentioned.

U. BRAKE BLEEDING PROCEDURE (Gravity)

1. Attach a clean, clear plastic tube to right landing gear brake bleeder. Extend the free end of the tube to

a container partially filled with hydraulic fluid (MIL-H-5606). Check the end of tube is submerged in

fluid. Open bleeder 1 /2 to 1 turn.

2. Fill brake fluid reservoir, located on the firewall, with hydraulic fluid.

3. Check right hand toe brake pedal(s) in cockpit have been pulled full aft.

4. Pull hand brake handle and slowly pump master cylinder approximately 50 times or until hydraulic

fluid is observed passing through plastic tube at brake bleeder.

—NOTE—

Fluid level in reservoir must be maintained to prevent air from

entering system.



5. Pump right brake cylinder very slowly approximately 12 times. This will purge air from toe brake

cylinder system. Watch for any air forced through clear plastic tube during this operation. Verify air

has been forced from toe brake system.

6. Pump hand brake an additional 25 times or until no air is observed through clear plastic tube.

7. Tighten brake bleeder and remove plastic tube.

  1. Repeat steps 1 through 6 for left main landing gear.




V. BRAKE BLEEDING PROCEDURE (Pressure)

1. Place a clean, clear plastic tube on vent fitting on top of brake fluid reservoir. Extend the free end of

tube to a container partially filled with hydraulic fluid (MIL-H-5606). Verify tube end is submerged in

fluid.

2. Attach another clear plastic tube to right landing gear brake bleeder. Connect the free end of tube to

pressure source. Open bleeder 1 to 2 turns and pressure fill system with fluid.

3. With fluid continually flowing through system, SLOWLY and simultaneously actuate hand brake and

toe brake pedal, of side being bled, several times to purge air from cylinders. On dual brake installations,

actuate both pedals for brake being bled.

—NOTE—

By watching the fluid pass through the plastic hose fluid

r e s e rvoir and the bleeder fitting on gear being bled, check if

any air is left in system. If air bubbles are evident, filling of the

system must continue until all air is out of the system and a

steady flow of fluid is obtained If brake handle remains

s p o n g y, disconnect the bottom of toe brake cylinders (next to

pedal) and rotate cylinder horizontally or above horizontal and

use hand brake alone to purge air from system.

4. Close the open bleeder fitting to which the pressure hose is attached. Do not remove tube from fluid

reservoir until both brakes have been bled. Check brakes on the side being bled for proper pedal pressure.

Place cap on bleeder fitting.

—NOTE—

Remove any trapped air in the top of wheel brake unit by

applying pressure to the system with the brake hand lever and

slowly opening bleeder and releasing hand lever.

5. Repeat Steps 2 through 4 for left main landing gear.

6. Drain excess fluid from reservoir to fluid level with syringe.
Click to expand...
Problem with this procedure is, the air will travel up the tube faster than you can pump it down.
Always bleed from the bottom up. help the air to go to the reservoir.
 
Okay, the brakes are working again. Cliff notes:

Pressure bleed from the bottom up, meaning a $9 bug sprayer from Home Depot (or Lowes if you prefer blue over orange) with an inline on/off valve and clear vinyl tubing necked down to fit the bleed nipple (giggity) on the caliper. Don't bother with that $25 Cleveland bleeder adaptor (I bought one) because the tubing actually worked better. Build up some pressure in the bug sprayer (about 10 strokes or so...giggity) and turn on the inline valve (just a little bit to move the fluid to the end of the hose before you attach it to the caliper) then attach the hose to the bleeder (no safety wire required if tight enough) and open the inline valve all the way. Fluid should travel from the bug sprayer through the caliper and all the way through the master cylinders and into the reservoir (which should have clear line connected to the little breather tube on the cap) and out into another container to catch the fluid. Do this until no air can be seen in the tube leaving the reservoir.

Do the above for both sides, then:

Back bleed just as you would for a car by pumping the brake and holding it, then open the bleeder on the caliper (which by now is disconnected from the bug sprayer and only has a length of clear tubing still attached to the bleeder) until no air bubbles come out. If no bubbles come out within a couple of tries it is good and move on to the other caliper. This does two things: one, it makes sure no air is left in the system and two, it drains the reservoir back down so that when you remove the cap you won't get hydraulic fluid all over the place.

Having said that, on my test flight for the brakes....the vacuum pump decided to call it a career.

:sigh: The hits just keeeeeep ooooon comin.
 
If you don't figure out how air got in the system you will never get it to work right, no mater how many times you bleed the system.
 
Noted. However, I've had the plane for a year and a half now and the brakes worked fine one day and didn't the next with no leaks. All the 16 or so fittings that could be causing the problem, were all tight.
 
How do you fashion an airtight/fluid-tight junction at master cylinder port so fluid goes up your drain line rather than leaking all over the floor?
 
Unless you have a Cessna, you use the rag and crack method. Only place I drained anything was at the brake caliper.
 
....sounds like a mess waiting to happen.
 
A messy job indeed. Just did pads & rotors all around for the BMW, along with flushing/bleeding the system. Right front wheel was corrosion-welded to the hub-centric flange, but after 10 minutes of pounding with a rubber mallet it came loose...and anti-seize applied to make it easier next time.
 
wrbix said:
How do you fashion an airtight/fluid-tight junction at master cylinder port so fluid goes up your drain line rather than leaking all over the floor?
Click to expand...

Piper's master cylinders aren't the same as Cessna's. Cessna cylinders have that reservoir on top, with a vented plug and no seal around the plunger shaft. Piper's have an inlet port and an outlet port and are sealed around the plunger. Fluid pumped from the wheels up just passes through them to the reservoir on the firewall. No leaky mess inside the airplane.

Cessna:
0541138-19_016.JPG



Piper:
Piper-Pa-31-425-Pa-31P-Navajo-Aircraft-Cleveland-Brake-Master.jpg
 
So if everything is working perfectly the bleeding the brakes system coming from both brake calipers up to the reservoir and pumping both petals and handbrake will purge all the air out effortlessly and it will work the first try and can be done by yourself. If air is being allowed into the system somewhere, fittings, master cylinder, etc. Good luck! Very frustrating! And this can happen without a leak present. Also beware of old or bad hoses. Hard to swallow so much work when there was no problem to start with but if air was allowed into the lines then this could be the first time the master cylinders have been fully compressed in some time so patience and diligence will be needed. I have never had good luck with the MM procedure. Pressure bleeding piper brakes has not been very effective either.
 
Here's my method. I run a clear tube from the bleeder back into the reservoir where I can see it, but I have a special cap that I can pass the hose of a one-man automotive brake bleeder backflow check valve through. Then I insert that in the reservior to keep the fluid going only one way. Then I sit and pump the brakes like 300 times, and watch for any bubbles passing in the clear hose. Works great, other than the sore thigh and calf muscles.
 
Clark1961 said:
I did not know that.

Hmmm. Do I have to go drain all the fluid out of the brake systems that I've bled by myself?
Click to expand...
Yes, and you must replace it with two person fluid. Instead of 5606, you must use 5606/2 (the 2 person varient).
 
Timbeck2 said:
A bunch of air came out of the lines but I still have the problem. I'm almost at a loss. I'm wondering now if it is the master cylinder for that side.
Click to expand...
Getting a lot of air out is a good thing, But, yes it is the master cylinder, have it rebuilt.

You try this first.. TRY....flushing the system with stodard solvent. there is a possibility (remote) that the old fluid has coagulated in the master cylinder.

A master cylinder is a simple pump, when they act as yours, the tiny check valve in the pump/master cylinder is not working properly.
 
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Velocity173 said:
Possibly air in the lines. I imagine you have aluminum lines, so hard to check. Anytime I see bubbles in my Glasair nylon lines, the brakes are useless. Just had it happen the other day. Bleed and refill.
Click to expand...

Glasair? How many planes do you have
 
JAWS said:
Sorry, cut and paste malfunction.

Basically, push fluid up from the bottom. With each master cylinder and fittings wrapped in rags and pressure in the system from below, crack the hose fittings until clear fluid runs out then retighten. Start at the position closest to the caliper, then the next and then the next. Then run more fluid through until it is clear. Might take more than one time around.
Click to expand...
yes, pushing from bottom up is usually what works for me
 
luvflyin said:
Oh. Dos. I was getting ready to ask if Cessna gave you permission to build a 172.
Click to expand...

Nope, old hanger mate with the 172. He sold it and went with a little CTSW.
 
Tom-D said:
Getting a lot of air out is a good thing, But, yes it is the master cylinder, have it rebuilt.

You try this first.. TRY....flushing the system with stodard solvent. there is a possibility (remote) that the old fluid has coagulated in the master cylinder.

A master cylinder is a simple pump, when they act as yours, the tiny check valve in the pump/master cylinder is not working properly.
Click to expand...

Wow...old thread. I bled mine from the bottom up using a garden sprayer with a shut off valve. I pressured the lines from the caliper up until it came out the reservoir while I pumped the brakes including the parking brake. Its been going strong ever since and judging from the age of this thread, that's almost two years now. Dan Thomas is right, my brakes have so many lines they always feel spongy.
 
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