Brake Master Cylinder overhaul

Bob Turner

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Apr 4, 2018
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759
Surprisingly, I found Cleveland instructions for overhauling my 10-54 master cylinders over on the Shortwing Piper forum.

I bet every single toe brake Champ and Decathlon uses this cylinder, so accepting tips from knowledgable mechanics, and I will share what I learn when done.

First, getting these things out of the aircraft is easy with floorboards removed, and probably impossible for normal humans otherwise.

The "spring collar" at the bottom of the piston rod is probably threaded on. I say that because assembly instructions say to use Loctite 262, and they seem to indicate that you let it dry for 24 hours before assembly. I seriously doubt that. I will check the Loctite site.

Meantime, if anybody here has done this task, let me know if there are any tricks or "gotchas" involved. Most of my hydraulic experience is with Grove parts. Easy to repair. Similar to Cleveland except for the check valve.
 

Bob Turner

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Apr 4, 2018
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Well, done! Just in case any of you are mechanically challenged like me, here is the plan:
Floorboards first. Not terribly difficult, but takes some time. Removing them is trivial with floorboards out, and marginally possible with them in.
I got kits from Plane Parts Inc, with a Stat-O-Seal, three O rings, and a lock nut and snap ring. Under $13, and reasonable postage. I know that we are looking at five bucks worth of stuff, but I was pleased.
You need a good pair of lock ring pliers, and a short hunk of rope for reassembly.
 

Bob Turner

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Apr 4, 2018
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Sure. Have to do that tomorrow - almost installed #2 today, but flew instead. My intent is to post a bit more on how-to and O ring part #s.
 

Bob Turner

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Apr 4, 2018
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759
Look the same to me. Mine are cleaner; have a Cleveland tag pasted on them. Cleveland probably bought Gerdes.

image.jpeg
 

Bartman

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Thanks for the photo. I found two others in my stash but the two in the photo are the two best so they'll get cleaned up, rebuilt, and put back into use. My IA recommended I buy all new brake parts but when I told him the prices he said it'll be ok to use the old parts!!!
 

Paragriz

1978 Bellanca 7ECA
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Mar 29, 2019
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3
I rebuilt the master cylinders and calipers about 4 months ago on my ‘78 7ECA. All were leaking to one degree or another. Ordered rebuilt kits from Plane Parts and pads from Groves. I found the project to be a straight forward with minimal tools or experience required. Cleaned everything well with solvent. Checked for scoring on the cylinder walls. Mine were good, but I’ve heard others having to hone their’s. Removed nicks or burs on the piston shaft with a fine Scotchbrite pad, otherwise the bur will shred your brand new seal as it slides over it. Used a light lube during assembly. Be sure the snap ring in the master cylinder seats into its grove properly or you’ll find pretty red streaks down the belly of your aircraft. Took me a little bit to clean up that mess...... 🤨
 

Bartman

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I rebuilt the master cylinders and calipers about 4 months ago on my ‘78 7ECA. All were leaking to one degree or another. Ordered rebuilt kits from Plane Parts and pads from Groves. I found the project to be a straight forward with minimal tools or experience required. Cleaned everything well with solvent. Checked for scoring on the cylinder walls. Mine were good, but I’ve heard others having to hone their’s. Removed nicks or burs on the piston shaft with a fine Scotchbrite pad, otherwise the bur will shred your brand new seal as it slides over it. Used a light lube during assembly. Be sure the snap ring in the master cylinder seats into its grove properly or you’ll find pretty red streaks down the belly of your aircraft. Took me a little bit to clean up that mess...... 🤨
might be a good subject for a quick how-to video when the time comes to do mine. thanks for sharing the details of it.
 

Bruce

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Dec 22, 2018
Messages
206
Location
Knoxville TN
I just did mine kit # 199-516 Aircraft spruce # 08-00353 only comments are pay attention to small end of spring And which way it faces. next I used 5606 only for assembly I would not recommend mixing oils in the brake system, in automotive world If you use Petroleum Based product it will swell all the seals. Last item I placed The cylinder the snap ring facing up On bench and used a tool box drawer to compress the shaft wile removing snap ring and re installing it. Good luck with the end results.
 

Bob Turner

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Apr 4, 2018
Messages
759
Oh, ouch! I did not notice any difference in spring diameter or end contour. We’ll see, I guess; mine are installed.

I concur - use 5606 to lubricate during assembly. Just takes a drop or two.

Plane Parts uses MS parts with date codes - $12.95 with extra snap ring and jam nut. Not sure how the jam nut wears out. Spruce; just the O rings and Stat seal - $29.95.

Necessary parts
MS28775-111, 112, and 012 - under a buck each. Stat O Seal 095-26200 - don’t know where you buy this part separately; probably under $4. Easier to buy the Plane Parts kit.

You need a very small flat blade screwdriver or an O-ring pick, a snap ring pliers, a short hunk of cord, and a few drops of 5606. Also need a small pair of regular pliers, a piece of cardstock to avoid scarring the little collar, and Loctite 262.

Disassembly is straightforward, but use the cord to compress the spring. A loop, wrapped around the fork and the outlet fitting, will do it. Snap ring removal is the hardest part - use the small screwdriver once you have the snap ring compressed. See photo for a version of snap ring pliers. Ignore my nails; couldn’t find the proper points.

Put the jam nut and fork in a vise, and gently undo the threaded on collar. Use the card stock and small pliers.

The whole thing comes apart - the Stat O Seal takes some coaxing, because it has an indent on the piston rod. Replacing the O rings is easier than it looks; that internal ring just jumps into place. Re-assemble with a drop of 5606 on each rubber part and a coat on the piston rod.

Clean the threads with alcohol or something, then a drop of Loctite and the collar. Almost done - 24 hrs later, assemble into housing, put the cord back on to compress the spring, and insert the snap ring. Nice to have new ones. They just go right in.2E649F3A-34B0-43A5-B978-10C12E9A4FD6.jpeg