Cleaning out the brake system

[Timbeck2]

I’m going to replace all the hoses and rebuild all 5 master cylinders. Only hoses I’m not replacing are the ones from the hard line to the calipers as they are only a couple years old. My question is, what do you A&Ps use to clean out all the old 5606 prior to disassembly if anything?

 

[Dan Thomas]

I’m going to replace all the hoses and rebuild all 5 master cylinders. Only hoses I’m not replacing are the ones from the hard line to the calipers as they are only a couple years old. My question is, what do you A&Ps use to clean out all the old 5606 prior to disassembly if anything?

Just blow out the old fluid and take it all apart. Should do the calipers, too, if they haven't been opened for a long time.

I'd be reluctant to put anything other than 5606 in the system to clean it. Most of the sludge will be where the fluid doesn't move much, such as the bottoms of the caliper cylinders.

 

[FORANE]

I've switched to royco 782 for a higher flash point.

 

[JAWS]

Isopropyl Alcohol (IPA).

If using to clean out hoses or hard lines, push IPA through one direction, then another, until it runs out clean. Then purge with dry shop air or nitrogen. Not to be used in assembled components (master cylinder, caliper, valves, etc). Components would use fresh 5606 purged through the component until the fluid leaving comes out clean.

Of course the most current instructions from the manufacturer would prevail!

 

[SoCal RV Flyer]

Should do the calipers, too, if they haven't been opened for a long time.

Definitely. Dunno how similar yours are to my Matco brakes, but without dust seals the edge of the piston gets eroded from little rocks and grit. I changed the pucks out along with the caliper O-rings. $15 well spent, and the old pistons make nice paperweights.

 

[Jdm]

My question is, what do you A&Ps use to clean out all the old 5606 prior to disassembly if anything?

Usually nothing prior. Purge system with fresh 5606 afterwards. Fresh 5606 does a great job of cleaning. Can normally accomplish this during the bleeding. If there happens to be an area that is particularly nasty you can always isolate and flush areas independently.

 

[Jim K]

Good luck, we're all counting on you.

Seriously, let us know how it goes. I've heard horror stories about bleeding piper brakes.

 

[FORANE]

I’m going rebuild all 5 master cylinders.

I've heard horror stories about bleeding piper brakes.

No kidding, 5 master cylinders? Really? Wow.

 

[Timbeck2]

No kidding, 5 master cylinders? Really? Wow.

Actually one master which is the hand brake and four slave cylinders, one for each toe brake.

 

[Timbeck2]

Good luck, we're all counting on you.

Seriously, let us know how it goes. I've heard horror stories about bleeding piper brakes.

I have a system which involves a garden sprayer. I pressure fill from the brake calipers all the way up to the reservoir

 

[Stewartb]

If you rebuild the masters you’re 99% there. Brake masters are probably #1 on the list of things guys should maintain but never do.

 

[Timbeck2]

Definitely. Dunno how similar yours are to my Matco brakes, but without dust seals the edge of the piston gets eroded from little rocks and grit. I changed the pucks out along with the caliper O-rings. $15 well spent, and the old pistons make nice paperweights.

I've got Cleveland brakes. I've already rebuilt the calipers when I replaced the pads at the last annual which involved cleaning all the internals and replacing the O rings. You got lucky, pistons are $97 apiece for me.

 

[mondtster]

If you rebuild the masters you’re 99% there. Brake masters are probably #1 on the list of things guys should maintain but never do.

Agreed. Most of the brake bleeding problems often associated with Cherokees can be avoided if the master cylinders are simply rebuilt. A lot of owners seem to balk at the idea but will happily pay for repeated attempts at bleeding brakes that won’t get better without more work.

 

[Domenick]

... Most of the brake bleeding problems often associated with Cherokees can be avoided if the master cylinders are simply rebuilt. ...

Why? How does rebuilding master cylinders make it easier to bleed the system?

 

[mondtster]

Why? How does rebuilding master cylinders make it easier to bleed the system?

My best guess is because air can enter the system around the plunger shaft yet largely go unnoticed as a problem. All I can say is that I’ve spent countless hours trying to bleed brakes on numerous Cherokees and other planes with similar systems. Every one of them bled easily after the master cylinder rebuilds.

 

[Timbeck2]

To be clear, I just want to evacuate as much 5606 out of the system as I can prior to replacing the 8 hoses and removing the cylinders inside the cabin. I've seen what 5606 does to carpet and no matter how careful one can be with rags placed on the floor and/or wrapped around fittings, it still makes a mess.

 

[Dan Thomas]

Good luck, we're all counting on you.

Seriously, let us know how it goes. I've heard horror stories about bleeding piper brakes.

Yup. Lots of fun.

 

[GeorgeC]

Yup. Lots of fun.

You keep using that word...

 

[Dan Thomas]

You keep using that word...

I've had lots of that sort of fun. I don't miss it much. Especially having 5606 on me and everything else. I'm glad I never had to deal with Skydrol.

One of the keys to bleeding those brakes is having someone pump the masters as you force the fluid up through the system. It helps to get the stubborn bubbles out.

 

[Timbeck2]

I've bled brakes before, on mine and other aircraft so that part isn't new to me and yes, it is a royal PITA and very frustrating. I've never replaced the hoses or rebuilt cylinders before so that will be new to me. And before anyone pipes up, I know I'm not allowed to replace any hydraulic hose as an owner which is why I'll have two A&Ps looking over my shoulder. Hopefully soon, that requirement will change.

 

[NealRomeoGolf]

I've bled brakes before, on mine and other aircraft so that part isn't new to me and yes, it is a royal PITA and very frustrating. I've never replaced the hoses or rebuilt cylinders before so that will be new to me. And before anyone pipes up, I know I'm not allowed to replace any hydraulic hose as an owner which is why I'll have two A&Ps looking over my shoulder. Hopefully soon, that requirement will change.

How close are you to your A&P rating now? I know you've been working on it.

 

[bflynn]

Tim, rebuilding cylinders isn't a complex task. The only tricks I can think of
1) roll any o-rings on, don't try to stretch them on.
2) Add the o-rings from the outside in
3) Keep the cylinder oriented as you rebuild it so you don't try to put it in backwards...ask me why I say that and why I say that cylinders should never be reversible.
4) Be gentle and inspect for nicks and scratches prior to rebuilding.

Otherwise, you get have all the fun of unsticking nuts that haven't moved in 30 years, etc.

 

[mondtster]

I've bled brakes before, on mine and other aircraft so that part isn't new to me and yes, it is a royal PITA and very frustrating. I've never replaced the hoses or rebuilt cylinders before so that will be new to me. And before anyone pipes up, I know I'm not allowed to replace any hydraulic hose as an owner which is why I'll have two A&Ps looking over my shoulder. Hopefully soon, that requirement will change.

The biggest suggestion I have is, don’t overlook the stat-o-seals that are likely in the master cylinders. The master cylinders aren’t fun to R&R so it would be a shame to do all that work replacing o-rings in the cylinders but retain the old seals.

 

[Timbeck2]

How close are you to your A&P rating now? I know you've been working on it.

I’m at the point now where I have the hours to make an appointment with the FSDO but I would like more experience so I don’t look like an idiot. I know they only want 51% but I’d rather be over 70%.

 

[Timbeck2]

The biggest suggestion I have is, don’t overlook the stat-o-seals that are likely in the master cylinders. The master cylinders aren’t fun to R&R so it would be a shame to do all that work replacing o-rings in the cylinders but retain the old seals.

The kits I bought have the complete set. I may have to order something different since I think there’s three different types of cylinders. Two types of Cleveland and three Gar-Kenyon cylinders

 

[Jdm]

I recently changed a number of hoses and hydraulic fluid on a PA28 with 5 master cylinders. I also needed to flush the system and clean the sludge from the bottom of the reservoir.
Here’s my “only child technique” for bleeding:
Get about 25’ of clear tubing the size of the bleed fittings. Safety the ends to the bleed fittings. Cut the tubing at the halfway point. Place the two open ends into the reservoir. Tape the tubes up and over the windscreen so that they are visible from the cockpit. With fluid already in the reservoir, sit in the cockpit and start pumping one master cylinder at a time. Watch the fluid/air travel through the tubing across the windscreen. Pump until there’s no air. Repeat for each master cylinder.

 

[mondtster]

Here’s my “only child technique” for bleeding:
Get about 25’ of clear tubing the size of the bleed fittings. Safety the ends to the bleed fittings. Cut the tubing at the halfway point. Place the two open ends into the reservoir. Tape the tubes up and over the windscreen so that they are visible from the cockpit. With fluid already in the reservoir, sit in the cockpit and start pumping one master cylinder at a time. Watch the fluid/air travel through the tubing across the windscreen. Pump until there’s no air. Repeat for each master cylinder.

That is a good way to bleed the brakes. I’ve used that technique to get the air out of some really stubborn systems.

 

[Timbeck2]

I recently changed a number of hoses and hydraulic fluid on a PA28 with 5 master cylinders. I also needed to flush the system and clean the sludge from the bottom of the reservoir.
Here’s my “only child technique” for bleeding:
Get about 25’ of clear tubing the size of the bleed fittings. Safety the ends to the bleed fittings. Cut the tubing at the halfway point. Place the two open ends into the reservoir. Tape the tubes up and over the windscreen so that they are visible from the cockpit. With fluid already in the reservoir, sit in the cockpit and start pumping one master cylinder at a time. Watch the fluid/air travel through the tubing across the windscreen. Pump until there’s no air. Repeat for each master cylinder.

which one do you start with? After you’ve gone through all of them do you start all over again?

 

[Timbeck2]

51% of what?

14 CFR 147 appendix B C and D

Don't want you to have to look it up but its a list of things A&P candidates should know. Some of which some mechanics will never know such as repairing wooden aircraft, composite, etc. I should know or at least be familiar with 51% of the things on that list.

 

[Jdm]

That is a good way to bleed the brakes. I’ve used that technique to get the air out of some really stubborn systems.

Yep, it usually works well.

which one do you start with? After you’ve gone through all of them do you start all over again?

I’ve always started with the pilot side, but doubt it makes any difference. Pilot, copilot, then parking brake order worked great for me. Brakes were rock solid after achieving about 3 clean pumps.

 

[Timbeck2]

Update:

I finally became a contortionist today and started on the hoses/master cylinders starting from the left brake on the pilot's side. So far I've replaced the hose from the MC to the hard line for the left brake. Looked at the data tag: Manufactured July 1969. My plane is a '70 model so that was the original hose and yes, it crackled when I bent it. Took the Gar Kenyon MC apart albeit with multiple stab wounds with a pick to get that tiny little circle lock ring out. I replaced all the O rings and the statoseal or rather what was left of it. The metal part was still there but the rubber part was mostly gone with a tiny sliver about 1/8" long and this is the side that was working! The right side brake is the side I lost. I'll tackle that this week after work. I'm looking forward to brakes that work reliably when this is all done but I'll admit, I've having nightmares about the hand brake. Looks like I'm going to have to remove the plastic console to get to it. Those who complain about the high labor charges on airplanes...I invite you to do what I did today. I've known for quite some time why it takes so long to do certain jobs on aircraft. I've also learned along the way that a lot of mechanics take the easy way out and don't fix it right the first time.

The whole time I'm taking this apart, @Dan Thomas ' words kept coming back to me and I paraphrase, "Those old hoses and brake cylinder seals don't owe you anything if they've been in there that long." He didn't say it to me, he said it to someone else on the forum but truer words were never spoken. Although all this is under the panel and a royal PITA to get to, it's actually kind of fun rebuilding those masters.

 

[Dan Thomas]

Update:

I finally became a contortionist today and started on the hoses/master cylinders starting from the left brake on the pilot's side. So far I've replaced the hose from the MC to the hard line for the left brake. Looked at the data tag: Manufactured July 1969. My plane is a '70 model so that was the original hose and yes, it crackled when I bent it. Took the Gar Kenyon MC apart albeit with multiple stab wounds with a pick to get that tiny little circle lock ring out.

Get proper circlip pliers. Much safer, less likely to damage yourself or the cylinder, less likely to lose the clip. Start filling that toolbox

 

[Jim K]

Those who complain about the high labor charges on airplanes...I invite you to do what I did today

For real. The amount of time I've spent on my back under the dash is certainly less than you've done on this project, but was enough to convince me that good mechanics are cheap. When my guy does some work for me outside of his part 145 job I try to be extra generous; I need to come up with something for him for Christmas.

 

[Timbeck2]

Get proper circlip pliers. Much safer, less likely to damage yourself or the cylinder, less likely to lose the clip. Start filling that toolbox

I have a really nice set of snap ring pliers but nothing that will fit this thing unless you're talking about a special tool. This little circlip required a loupe to actually see the gap in it. To the naked eye it appeared to be just a ring and is a little bit bigger than the refresh the page icon on your screen. The new one went on a lot easier than the old one came off. Here it is in the center which is depicted a tad larger than actual size. Statoseal left center was what I was talking about before (that wasn't for you, you of course know what it is)

 

[SoCal RV Flyer]

Panel dives truly do suck. You get cramps in muscles where you didn't know you had muscles.

The key is to have every conceivable tool you'll need in the other footwell, so you can remain in the panel dive position for the duration of the job. Of course that never works because you always need another tool or part!

Glad you got the job done. Truly satisfying to do it yourself, learn about how your plane works and save significant AMUs.

 

[Timbeck2]

Glad you got the job done.

Oh it isn't done yet. The hand brake was removed along with the right pilot's MC and both co-pilots MCs. On the hand brake, someone had used a thin washer instead of thick at the top of the spring which was chewed up and scraped the shaft a little. Since it was not in an area where it is near an O ring, I just polished it out and replaced the washer with the proper type. Rebuilt all the masters without incident and found one of the hoses was cross threaded to the tee fitting on the co-pilot's left master cylinder. This was an obvious leak and it quite likely the source of my issues. Since the kits I bought didn't include the correct size roll pin, I'm now dead in the water for want of two roll pins...just two and the airplane Gods want about $13 per. I found that the right side hoses were installed in 2006 which leads me to believe the right side brakes were installed at the same time. We also bent two roll pin punches trying to get the old ones out...good times. I will also say that the cylinders are easier to install than to remove for some reason.

So I have a little project creep but I should be ready to bleed the brakes and fly it by the end of the week.

 

[SoCal RV Flyer]

Oh it isn't done yet. The hand brake was removed along with the right pilot's MC and both co-pilots MCs. On the hand brake, someone had used a thin washer instead of thick at the top of the spring which was chewed up and scraped the shaft a little. Since it was not in an area where it is near an O ring, I just polished it out and replaced the washer with the proper type. Rebuilt all the masters without incident and found one of the hoses was cross threaded to the tee fitting on the co-pilot's left master cylinder. This was an obvious leak and it quite likely the source of my issues. Since the kits I bought didn't include the correct size roll pin, I'm now dead in the water for want of two roll pins...just two and the airplane Gods want about $13 per. I found that the right side hoses were installed in 2006 which leads me to believe the right side brakes were installed at the same time. We also bent two roll pin punches trying to get the old ones out...good times. I will also say that the cylinders are easier to install than to remove for some reason.

So I have a little project creep but I should be ready to bleed the brakes and fly it by the end of the week.

Oh, the project that keeps on giving...or taking, depending on your perspective. I've had a few of those.

 

[Timbeck2]

Parts are in. I'll finish it tomorrow or Thursday and do the one man or "only child" method of bleeding the brakes as suggested above. I've mapped out the flow of 5606 from the reservoir through all the master cylinders and out to the calipers. I'm going to attempt to pump the cylinders in order from the flow. The only sticking point I see may be at the tee fitting on the co-pilot's left brake master cylinder. Maybe it will work, maybe it won't.

 

[Snowmass]

In 8000 hours and 50 years I have never flushed out a hydraulic brake system and never had a problem. Also, I now put 15% Granville Strut Seal in ALL my hydraulic systems since it reconditions rubber. As to bleeding brakes the basic physics is the same: push the fluid through the system faster than bubbles can migrate back.

 

[Timbeck2]

It is finished. I am sore. The "only child" method worked and I only had to bleed the top fittings of the master cylinders on two of them, both on the co-pilot's side. And with over 20 joints in the system, only one leaked and was quickly tightened up.

I have brakes again.