PA28 hand and toe brake fluid leaks, parts, etc...

MuseChaser

MuseChaser

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MuseChaser
'65 PA28-140 Cherokee ... has had small hydraulic fluid leaking onto pilot's sheetmetal foot/heel pad since owned (ten years?). Not enough to need topping off more than very, VERY occasionally, but enough that I want to address it before putting in new carpeting. Crawled under there today to get a good look-see. The left toe-brake cylinder itself appears to be leaking, and the L fitting coming off the handbrake cylinder looks like it's leaking where the hose is screwed onto it. Just so no one yells at me, I'm trying to do as much "legwork" as I can before enlisting my A/P.. I'm not doing this myself. He has suggested I look more closely at the handbrake master cylinder, as he feels it's more likely for the handbrake leak to be coming from there and running down onto the elbow.
NOW... the scary parts..
The handbrake cylinder is part # 455 930, Cleveland master cylinder... for $855?!?!??!
The toe brake cylinder is part # 455 932 Cleveland 10-20 $419, #455 948 Cleveland 10-27 which I can't find anywhere, #455 968 Cleveland 10-30 $429, or #455 944 Gar-Kenyon 17000 which I can't find, although there are seal/rebuild kits for the 17000 or 10-30 cylinders available for just north of $30. Catch is... I'm not sure which cylinder I have in may plane. Will have to snap a pic of the parts diagrams and take it out to the plane tomorrow, and hope that the cylinders I have are the ones that have rebuild kits available.

Hard to believe a very, very small leak may cost $855 plus $430 (maybe times two if the right toe brake cylinder should be replaced too) just in parts. Anyone have any experience? Better sources? Rebuild kits for 10-20, 10-27, or 10-22 cylinders available anywhere? Searching by the Piper part numbers isn't always very fruitful... I'd leave all this up to my A/P, but I'm on a shoestring and the more I can do out front for him the better. Plus, well... the more I learn, the better.

Thanks..
 
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A common thing for Cherokee mechanics to do is bleed brakes from the area/s you mentioned. Perhaps all you need is to tighten up the fittings.
 
THAT, my friends, would be incredibly awesome if that's all it is, and my Mark IV eyeballs tell me that that is a distinct possibility for the leakage at the handbrake cylinder elbow. Unfortunately, the left toebrake leak really looks like it's coming out onto the piston at the bottom of the cylinder. I'll take another long hard look tomorrow, and see if a little judicious gentle tightening does anything. I really hope you're correct!
 
Those things often have standard O-rings in them. MS28775-XX for piston and rod seals, and MS28778-XX for the fitting seals against the cylinders. Can't quote the actual numbers. They age and start leaking. If they haven't been off in ten years they don't owe you anything.
 
By the way, listen to Dan before me. He's the experienced mechanic, I'm not.....yet.
 
Have rebuilt a few sets over the years. As I recall, Orings were called out for each cylinder in maintenance manual in an exploded diagram. There was a small plastic check valve that I ordered from piper and replaced during rebuild as well. It wasn't terribly difficult, just tedious. I did all 5 together since I was not keen on doing this again anytime soon.
 
Definitely just replace the O-Rings and then bleed.
 
Rebuilding a cylinder valve like this is not difficult. I presume it’s permitted, although I don’t know that. If so, the cost is a few dollars for o-rings, nowhere near 1000.

Look around and see if you can find the specs on it. The most common cause of hydraulic leakage is flattened o-rings.
 
focal_plane said:
Have rebuilt a few sets over the years. As I recall, Orings were called out for each cylinder in maintenance manual in an exploded diagram. There was a small plastic check valve that I ordered from piper and replaced during rebuild as well. It wasn't terribly difficult, just tedious. I did all 5 together since I was not keen on doing this again anytime soon.
Click to expand...

I don't have toe brakes for the copilot, so I'm looking at three cylinders.. master and two toes. After poring over the IPC and service manual, I'm still kind of confused as to what I'm looking at; I've attached shots of the pertinent IPC (with the yellow 1 indicating the complete cylinder assembly, 2 the exploded diagram of my specific cylinder, and the 3 the exploded diagram of the 10-22 cylinder found in subsequent aircraft... I think?) and service manual diagrams for my specific serial number. The service manual, diagram 7-16, shows O-rings at locations 2, 3, and 6, and the service directions say to "install the new O rings (2 and 3) on the cylinder plug (1)," then, "Install the cylinder actuator piston (5) on teh actuator shaft (4) and secure with the roll pin (7)." So far, so good, and the part numbers for O-rings 2 and 3 are shown on the IPC diagram as 7 and 8, AN6227-7 and AN6227-11 respectively. The next step in the SM is "Install a new O ring (6) on the actuator pin." That's where I get confused. If you look carefully, you'll see part 6 indicated in the service manual diagram (reinforced by me w/ the yellow "6?"), but parts 5 and 6 in that diagram are named "cylinder actuator piston" and "piston," respectively, and there's no mention anywhere of an "actuator pin." To make matters more confusing, the IPC doesn't indicate that O-ring at all in the exploded diagram I've circled and marked "2" below.

Maybe I'm just confused by the terminology. The item I've indicated as "1" in yellow below is described in the IPC as "Actuator Assembly - Brake cylinder," P/N 63353-00, but the footnote says to order P/N 455 938 if "complete actuator assembly is required." That part number cross references to Cleveland 10-22, which is what is shown exploded in yellow #3 below, indicated as part 40 and found on later serial numbers than my plane.That part is described as "Cylinder Assembly - Master (10-22)." Are "actuator" and "cylinder" interchangeable? I thought the actuator was the piston and shaft, and the cylinder was the housing (shown as 9 in the SM diagram on the right below).

I'm sure that my A/P will know exactly what to do once we get started, and who knows, maybe it'll be self-evident to me at the time, too, but I'd like to make sure we have all the correct parts on hand before starting. What is this mystery "O ring 6" that the SM refers to?

Sigh.. thanks for any help... sooo confused. The toe brake cylinders can be one of four, so I'll have to check that out further in person. The good news is that the diagrams for those four in both the SM and IPC are much clearer and I can figure that out.



IPCCyl.jpg SMCyl.jpg
 
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focal_plane said:
..There was a small plastic check valve that I ordered from piper and replaced during rebuild as well. It wasn't terribly difficult, just tedious. I did all 5 together since I was not keen on doing this again anytime soon.
Click to expand...
EppyGA said:
Definitely just replace the O-Rings and then bleed.
Click to expand...

bflynn said:
Rebuilding a cylinder valve like this is not difficult. I presume it’s permitted, although I don’t know that. If so, the cost is a few dollars for o-rings, nowhere near 1000.
Look around and see if you can find the specs on it. The most common cause of hydraulic leakage is flattened o-rings.
Click to expand...

LOL.. thanks, all... that's the idea, and you all chimed in as I was trying to write that last post clearly. Much appreciated.. it's identifying some of the O-ring part numbers that's driving me nuts. Can any of you decipher this further for me? I'd be happy to attach pics of anything else that might help.
 
MuseChaser said:
I don't have toe brakes for the copilot, so I'm looking at three cylinders.. master and two toes. After poring over the IPC and service manual, I'm still kind of confused as to what I'm looking at; I've attached shots of the pertinent IPC (with the yellow 1 indicating the complete cylinder assembly, 2 the exploded diagram of my specific cylinder, and the 3 the exploded diagram of the 10-22 cylinder found in subsequent aircraft... I think?) and service manual diagrams for my specific serial number. The service manual, diagram 7-16, shows O-rings at locations 2, 3, and 6, and the service directions say to "install the new O rings (2 and 3) on the cylinder plug (1)," then, "Install the cylinder actuator piston (5) on teh actuator shaft (4) and secure with the roll pin (7)." So far, so good, and the part numbers for O-rings 2 and 3 are shown on the IPC diagram as 7 and 8, AN6227-7 and AN6227-11 respectively. The next step in the SM is "Install a new O ring (6) on the actuator pin." That's where I get confused. If you look carefully, you'll see part 6 indicated in the service manual diagram (reinforced by me w/ the yellow "6?"), but parts 5 and 6 in that diagram are named "cylinder actuator piston" and "piston," respectively, and there's no mention anywhere of an "actuator pin." To make matters more confusing, the IPC doesn't indicate that O-ring at all in the exploded diagram I've circled and marked "2" below.

Maybe I'm just confused by the terminology. The item I've indicated as "1" in yellow below is described in the IPC as "Actuator Assembly - Brake cylinder," P/N 63353-00, but the footnote says to order P/N 455 938 if "complete actuator assembly is required." That part number cross references to Cleveland 10-22, which is what is shown exploded in yellow #3 below, indicated as part 40 and found on later serial numbers than my plane.That part is described as "Cylinder Assembly - Master (10-22)." Are "actuator" and "cylinder" interchangeable? I thought the actuator was the piston and shaft, and the cylinder was the housing (shown as 9 in the SM diagram on the right below).

I'm sure that my A/P will know exactly what to do once we get started, and who knows, maybe it'll be self-evident to me at the time, too, but I'd like to make sure we have all the correct parts on hand before starting. What is this mystery "O ring 6" that the SM refers to?
Click to expand...

Number 6 is the piston. 5 looks to be the O-ring. That IPC is messed up. You can determine the O-ring number if you measure the cylinder bore and piston groove inner diameter and width and use an O-ring chart to get the number. It might even be the same part number as #2, if there are no steps in the bore. A chart an be found in the Federal Mogul catalog: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwjBw-Chq_jhAhUSZKwKHcELD-kQFjAAegQIARAC&url=http://www.allsealsinc.com/pdf/National%20O-Ring%20Catalogue-1.pdf&usg=AOvVaw1PPLt2YIIIn8BM5OfXk-xi

Edit: better yet, use the Parker catalog: https://www.google.com/url?sa=t&rct...D%205700.pdf&usg=AOvVaw2Er01nQfvt82gTk3Y2n6B5

Scroll down to Page 129 of the pdf.


You take that dash number (for example, -016) and make it the suffix for the MS28775 aircraft O-ring: MS28775-016.

AN6227 O-rings are now MS28775: https://www.lasaero.com/products/article/L04I65CWT
 
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Thanks so much, Dan.. great resources. Looks like I can't find out for sure which exact o rings I'll need until we disassemble the cylinder and measure it, given the wonky nature of this part of my SM and IPC. I'm assuming my A/P will have a stock of appropriately sized rings, but I was hoping to just bring what i need with me in order to be as helpful as I can.
 
This is where Piper shines in the simplicity and cost of maintenance. The Piper toe brake cylinders and parking brake mechanisms are dead simple, and as others have posted it's usually the 'O'-rings that fail in the former. The only time I have ever seen a cylinder assembly need replacing is when the brake fluid was so old it absorbed enough moisture over time to corrode the interior of the cylinder, and it could not be salvaged.

The other common problem with Piper hydraulic systems is where a fitting is threaded into a cylinder (or in the case of my Aztec, the hydraulic power pack). The main part is usually a tapped NPT thread. Those joints seem to like to weep after a long time in service.

Any mechanic with Piper experience can replace the 'O'-rings - they are common inventory in every maintenance shop I've ever dealt with the five Pipers I've owned. It takes more time to get the cylinder in and out of plane than it does to rebuild it.
The NPT thread leaks require removing the fitting, cleaning the threads thoroughly and re-assembly with proper thread seal. TIghtening them has never, ever worked for me so far.

All in, cheap as chips compared to most other aviation repairs.
 
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I just had three master Cylinders rebuilt on my Lance. It wasn't even speed bump in the monetary department. Parts were cheap and labor was insignificant.
 
You best get your A&P involved prior to attempting this job.
 
Unit74 said:
I just had three master Cylinders rebuilt on my Lance. It wasn't even speed bump in the monetary department. Parts were cheap and labor was insignificant.
Click to expand...

Just because I'm feeling frisky tonight, a snap of my invoice:
Brakes.jpg
 
@JAWS ..... and the peasants rejoiced! Thank you sooo much...exactly what I was looking for!

@Tom-D ... re/ getting my A/P involved..wouldn't do it any other way. Tried to make that clear.
 
JAWS said:
I have an old hardcopy of the Parker Product Manual at work. The on-line one is below. Piper PA28 master cylinders start at page 43-ish. Better breakdown pictures.

https://www.parker.com/literature/Aircraft Wheel & Brake Division/AWB Static Files for Literature/AWBPC0001.pdf

I like the Aviall cross reference guide. Been using it for many years in the old paper catalogue.

https://www.aviall.com/medias/0036....yYzI0YzdlNDYwNzFkNjc5NDk2NzQ2&attachment=true
Click to expand...

Yes. Much better! Thanks.
 
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