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Brake Return springs

I have seen it mentioned several times about having a spring return on the brake pedals. What tension or strength and length do they require? I am sure someone has done their homewok that did this and I would appreciate any info.
Thanks George Z
 
Parts List

RV Brake Spring Parts List

I used the following from McMaster Carr
www.mcmaster.com/

(1) Pkg 6389K625
Nylon Bearing Flanged, for 3/8" Shaft Dia, 1/2" Od,
3/8" Length, Packs of 5 $1.97 Pkg

(1) Pkg 9657K115
Steel Compression Spring Zinc-Plated Spring-Tempered, 3"
L, 1/2" Od, .047" Dia, Packs of 12 $5.29 Pkg

(4) Ea. 9946K13
Aluminum Set Screw Shaft Collar 3/8" Bore, 3/4"
Outside Diameter, 3/8" Width $1.82 EA.

for a total cost of about $19.62 with shipping.
 
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If I understand correctly; the Cleveland master cylinders require the springs but the Matco's do not.

I could be wrong.
 
If I understand correctly; the Cleveland master cylinders require the springs but the Matco's do not.

I could be wrong.

You have it backwards.

Matcos and Clevelands both have return springs, however the Matco has them internal and the Clevelands have them external...

But for some reason, the Matco units sometimes need a little extra, so a second spring can be added to the exposed shaft.

I have had both apart, side by side, and the main area I can see that might cause the problem is the "Free play" at the end of the return stroke. The Matcos have very little, and the Clevelands have close to a quarter inch of free play.
 
I just did this installation as a retro fit, and had no trouble adding the springs while under the panel.

Regards,
 
How far down the shaft should the collar be? I'm looking for the best ompromise between peformance and pedal travel. Also, once the brake system is full, how much pedal travel should you have?
 
My collars are about 3/4" from the top attach point of the master cylinders. This seems to give me enough tension to return the pedals to neutral with enough authority. No need to over do it, but your foot will compensate for any over loading of that spring IMHO.

As far as pedal travel, you really need to get a feel for the resistance you have in the brake. If you feel that it is spongy and has excessive travel, then you have air in the line somewhere. Once you bleed those lines, you should feel firm resistance to pedal application after about 2"of deflection...at least that is what I am getting.

Hope this helps
 
Are you sure?

Once you bleed those lines, you should feel firm resistance to pedal application after about 2"of deflection...at least that is what I am getting.

Two inches is a huge amount of peddle travel for the brake peddles in any RV.
If the system is working properly with no air in it anywhere, the peddle travel should be more on the order of 3/4 inch maximum travel at the top of the peddle. That's been my experience anyway, with the dozen or so RV's I have worked on.
 
Springs

There is a person here at DVT that has made up a kit consisting of 8 step bushings and 4 springs. Bushings for the top rest against the washers and the bottom to protect the cylinder housing. Most of the locals now have them installed and love them. I think he wants 25 bucks and well worth it. If interested send me a PM and I'll give you the contact info. Larco
 
Keep it simple

You really don't need all of the fancy collars, etc for this fix. (Although go for it if you like.)
All you really need is the two springs, which you can pick up at HD, Lowes or a local spring shop (Ace Spring, here in San Antonio) for about $2 or less, and some washers, which you probably already have.
Just take the top of the brake master attachment loose at the top of the pedal, freeing the shaft. Slide on a fender washer, then the spring and then another fender washer. (I forget what size washers were needed, but they were a regular AN size, maybe AN5. For the correct spring length, measure the length of the shaft that is exposed and get one a little longer and of a diameter that just fits over the shaft.) If the spring needs more tension, just add some additional smaller washers at the top and put the AN3 bolt back on. Finished!
I did this and it worked great, eliminating the tendency for my brakes to drag. It is also something that you can do without disassembling the rudder pedals, etc.
Good luck.
 
MDS filled Nylong bushings?

I used the following from McMaster Carr
www.mcmaster.com/
(1) Pkg 6389K625
Nylon Bearing Flanged, for 3/8" Shaft Dia, 1/2" Od,
3/8" Length, Packs of 5 $1.97 Pkg
(1) Pkg 9657K115
Steel Compression Spring Zinc-Plated Spring-Tempered, 3"
L, 1/2" Od, .047" Dia, Packs of 12 $5.29 Pkg
(4) Ea. 9946K13
Aluminum Set Screw Shaft Collar 3/8" Bore, 3/4"
Outside Diameter, 3/8" Width $1.82 EA.
For anyone who has used these, can the spring be wound around the outside of the flanged Nylon bearing? I'm thinking of using a bearing at both ends.

I'm also considering using a slightly different part number for the bearing (6294K89) which is the "MDS Filled Nylon" version. It is slightly cheaper but more importantly (from the McM-C website):

MDS-Filled Nylon? Provides the same qualities as nylon, with the addition of wear-resistant molybdenum disulfide (MDS), which makes it self lubricating

Anyone have experience with these?
 
SPRINGS

George

I found that replacing the bolts that the pedal pivots on did more to help the brake release than the springs did. We replaced he 2 short bolts with one long bolt, I don't remember the length, but I'm sure someone here could tell you. With 2 short bolts the pedal tends to bind on the bolts if there is any play from side to side, with a single bolt this is eliminated.
 
A Simple Way...

RV6A419BrakeSprings.jpg


All I did was buy some 5x1/2 inch springs at Ace. I don't think you need washers or anything else...
 
Replacing my bungy cords

I will be replacing my (aircraft quality) bungy cords with springs this week. Found everything I need ( thanks to some great pictures posted in the threads) at Lowe's and H-D. Bungy cords worked fine for a temporary fix -- but they look tacky and the colors did not match my interior.
 
Current Prices from McMaster

(1) Pkg 6389K625
Nylon Bearing Flanged, for 3/8" Shaft Dia, 1/2" Od,
3/8" Length, Packs of 5 $2.26 Pkg

(1) Pkg 9657K115
Steel Compression Spring Zinc-Plated Spring-Tempered, 3"
L, 1/2" Od, .047" Dia, Packs of 12 $6.00 Pkg

(4) Ea. 9946K13
Aluminum Set Screw Shaft Collar 3/8" Bore, 3/4"
Outside Diameter, 3/8" Width $1.91 EA.
RV Brake Spring Parts List

I used the following from McMaster Carr
www.mcmaster.com/
....
 
You really don't need all of the fancy collars, etc for this fix. (Although go for it if you like.)
All you really need is the two springs, which you can pick up at HD, Lowes or a local spring shop (Ace Spring, here in San Antonio) for about $2 or less, and some washers, which you probably already have.
I just did what Steve did too. I got the springs at Ace (Home Depot and Lowes didn't have nearly as good a selection). They are 5/8" x 3"x 080 compression springs. Four of those and 8 stainless steel 3/8" washers (2 washers per master cylinder) cost about $8.00. Plenty of spring back, and more could be had if necessary just by adding a few washers. Also, with this setup, no worry that a collar/set screw might come a bit loose later without knowing.

 
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RV6A419BrakeSprings.jpg


All I did was buy some 5x1/2 inch springs at Ace. I don't think you need washers or anything else...

Matco tech support advised me against using spring without any protective washer/bushing on the shaft as it could damage/scratch the shaft. If you are going to add spring, then use all the appropriate washers and plastic bushings.

Regards
Mehrdad
P.S. there seem to be a lot of air in those lines.
 
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I did the Home Depot springs and washers and they work great. HOWEVER, the longer bolts did just as much or more than the springs. Suggest you do them both. The corect dimensions for the bolts can be found via "search". This really does help as does building up the bottom of the brake pedals is also a good idea.
 
I did the Home Depot springs and washers and they work great. HOWEVER, the longer bolts did just as much or more than the springs. Suggest you do them both. The corect dimensions for the bolts can be found via "search". This really does help as does building up the bottom of the brake pedals is also a good idea.
Thanks, Ken. I tried that, but to use the long bolt you have to have drilled through originally with a long drill bit and/or been perfectly straight as you drilled through the thick brake pedal angle. Getting the holes on both sides of the pedal to align perfectly is a must, otherwise the long bolt merely binds up the pedal more than individual bolts on each side do.
 
Thanks, Ken. I tried that, but to use the long bolt you have to have drilled through originally with a long drill bit and/or been perfectly straight as you drilled through the thick brake pedal angle. Getting the holes on both sides of the pedal to align perfectly is a must, otherwise the long bolt merely binds up the pedal more than individual bolts on each side do.

This is one place where a sloppy bolt fit is OK. Just file the holes out till the long bolt slides through without any drag.
 
Bolt size

The bolt size I'm using is AN3-56
Expensive $45.00 for both sides from Spruce.
 
I added springs to my brakes tonight. I used 3, 3/8 stainless washers from ACE and 3 x 19/32 x .054 springs from McMaster-Carr. These springs have 7.49 pounds of compression under load. I went with lighter springs because my hinge bolts are long, through bolts and are very smooth. I did it like Alpinelakespilot2000.

My hinge bolts are AN3-60 bolts from Spruce ($10.90 ea) and I needed 2 washers under the nut. My brakes are very smooth and free. These bolts are fairly dear but, you get a nice, smooth hinge with a single bolt.

The springs come in a bag of 12 so, I have 8 extra springs if anyone wants them. 90 cents for each spring and $5.20 shipping (US); send a PM. The springs cost $10.41 with shipping from Mcmaster-Carr so, you can save a couple of bucks if you want my extra. I'm just looking for my cost and the Post Office's cut. I schlepped all over for an afternoon and didn't find suitable springs locally.

Definitely best to do this before riveting the top skin. Even with that, it took some contortions to add the springs.

Jekyll
7A Slider
 
I'll take four!

I will take four of your extra springs. I think that adds up to $8.80. let me know your address.
RV9A Bill
 
I have brakes that drag slightly when there is pressure applied to the bottom of the rudder pedals. Unless I am very careful, meaning, I taxi with my feet OFF the pedals, just tapping them whenever I need correction, there is no problem. On takeoff, with both feet on the bottoms of the pedals with slight pressure, my brakes drag. I talked to Van's and Ken S. mentioned how some builders were machining the holes 1/8" larger on the master cylinder to add some "slop", and give a little leeway so the problem I'm having doesn't occur. I know myself and one other RV-8 on my field have this problem. My question is, would this spring setup fix our issue?
 
It's the geometry!

The geometry of the RV8 rudder/brake pedal makes it very easy to apply brake drag while using the rudders to taxi. I think this is what you are referring to. Its is a well known issue and you can probably search on this forum to see different types of fixes. One popular fix is to replace the two short axle bolts, at the base of the pedal, with one long AN bolt that spans the entire pedal. This allows you push on the rudder only without actuating the brake at all. (You are actually using the bolt as the rudder bar, which does not apply any pressure to the brake.)
Another fix is to attach something onto the base of the pedal itself to keep from pushing the brake on. This is what I did. I used a piece of delron, about 1/2" x 1/2" by whatever the width of the pedal was and just attached from the back of the pedal with two #6 screws. It works great and the mod does not have any effect on flying at all. If you look at the pedal, from the side, you'll see that this method actually pushes the rudder and tends to put a little opposite pressure on the brake. (You could use a piece of wood, etc.)
There are probably other fixes that would work, but these do for sure.
I would guard against drilling the holes out too large and letting things slop around.
 
One more thing

I forgot to mention that the brake masters can still cause a slight drag, even after making the above mentioned mod, but not always. If it persists, then the springs need to be added.
you can test it by just trying to pull the plane forward on the ground. If the brakes are dragging, you'll be able to tell. (Actuate the brakes several times while testing this, since they can stick intermittently.) This means you probably need the springs. If they do not drag, then you are inadvertantly using the brakes while taxiing.
 
SPRINGS

Oh my!:eek: Here I am coming up on 5 years and 400hrs., WITH NO BRAKE SPRINGS and I didn't know I had a problem!!!!!:eek: ???Wonder why I still have the same tires I started with??? (No wonder they're going bald----;))
 
RV Brake Spring Parts List

I used the following from McMaster Carr
www.mcmaster.com/

(1) Pkg 6389K625
Nylon Bearing Flanged, for 3/8" Shaft Dia, 1/2" Od,
3/8" Length, Packs of 5 $1.97 Pkg

(1) Pkg 9657K115
Steel Compression Spring Zinc-Plated Spring-Tempered, 3"
L, 1/2" Od, .047" Dia, Packs of 12 $5.29 Pkg

(4) Ea. 9946K13
Aluminum Set Screw Shaft Collar 3/8" Bore, 3/4"
Outside Diameter, 3/8" Width $1.82 EA.

for a total cost of about $19.62 with shipping.

Resurrecting an old thread. It appears that I'm experiencing dragging brakes, so I'm going to try putting springs on to see if that helps.

So here's a dumb question, based upon the above parts list. How are you getting the spring which has an inside diameter of .406 over the flange that the outside diameter of .5?

I didn't pay attention to the dimensions and blindly ordered them off McMaster Carr. When I got the springs, they appear to be too stiff (or I'm too weak) to uncoil the ends a bit to get them over the flange end.

For the folks that used these parts, how did you accomplish getting the spring over the flange?

I've got .5 ID springs on order, but since this was a long thread several years ago, I'm curious on how people accomplished the task.

thanks,

bob
 
If you have?

If you have the Matco cylinders as we use on the two seat'ers, we have just been using the repair kits from Van's. They have a new spring in them along with all the new seals. I take the old springs and put them around a bolt, then roll them on a steel plate or such and peen them with a small ball peen hammer while rolling them to let the spring swell to the size that goes around the piston shaft. Then we put a 1/8" thick nylon washer down at the bottom of the shaft on top of the cylinder top. And then use a set screw caller to hold the spring with some ( just a little ) pressure on it. So it will return to the top of the travel every time. Just kid of what we found to work and it does very well.
Yours, R.E.A. III # 80888
 
I found that when I rebuilt my Matco master cylinders last year, I no longer needed the external shaft springs I had installed the year before. I assume that the cylinders were original to the build in 2000; I didn't find any documentation that they had been changed or rebuilt. I also found that the shaft had deformed, which caused the leak at the top of the assembly that was the reason for the rebuild.
 
Increased spring force

After a recent post in another thread from someone asking about brake return spring mods, I thought I should finally update this thread with my brake modifications. I assembled my Matco master pistons with the springs recommended in this thread and there was only a barely perceptible increase in return force. I subsequently took some measurements of the spring force in the matco's, ran a few calcs, and came up with an alternative spring solution that will double the current spring force. The original spring upgrade was a maximum of 6lb in compression. This one is 30lb. I've tested them out over the past week during my taxi tests and they feel perfect, with no risk of dragging brake, even if your toes are naturally leaning on the pedals, but not too much force that they become an incomberance when you want the brakes. I also modified the collar sleeve arrangement so that even at full brake compression, there is no way that the spring can rub on the ram. The sliding collar is also a self lubricating polymer, which should help with longevity. Just make sure when you assemble things that the collar is low enough to just clear the top mounting tab, but not so low that you restrict compression of the ram. My aircraft is an RV-7, and I would absolutely recommend the long-bolt (single axis) mod to the brake pedal to eliminate binding, in addition to the spring upgrade. You'll also see in the photos some another mod I did to make some standoffs. These are just aluminum split collars and a piece of tubing cut into thirds, then riveted in place with some long AN470AD4 rivets (the collars are countersunk on the inside and I back riveted it against an appropriate diameter bolt shank). I've also stacked two more short pieces of the cut tubing in between to give myself a little further distance.
Anyway the McMaster Carr parts list is as follows.
Spring 9657K435
Lower nylon sleeve bearing: 6294K441
washers (for seating the lower nylon sleeve bearing) 90295A470
Top nylon sleeve bearing: 6389K625
Set screw shaft collar: 9946K13

For the standoffs:
Two piece collar: 6436K136
Aluminum tubing: 9056K79

Hope this helps.
Tom.

ng3bcl.jpg

fozt77.jpg

2d9zl7p.jpg

2j3ml48.jpg
 
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Tom, great info------I took the liberty of copying it over to the sticky thread on brake problems in the " RV Ongoing Maintenance Issues" forum.

Will be much easier to find in the future, instead of only in the RV 8 forum.
 
Springs are a bandaid around a problem. Fix the problem and you don't need springs. Most people won't accept a system in their airplane that doesn't work properly. This seems to be an exception as folks readily go through the effort to add springs to a system that doesn't need them and wasn't designed for them.
I doubt the added springs will cause any issues, but why not get your pedals, bolts, etc... properly aligned so you don't introduce excess wear to those parts. You then won't need any additional springs.
Lots of help in the forums on how to do this right.
 
Wow...

One thing you overlooked with the addition of springs is brake feel. Even with perfectly adjusted pedals, linkages, etc., the return pedal force is minimal. The addition of springs gives a greater tactile "feel" to the brake pedals.

Of course, you are also entitled to your opinion, too...
 
One thing you overlooked with the addition of springs is brake feel. Even with perfectly adjusted pedals, linkages, etc., the return pedal force is minimal. The addition of springs gives a greater tactile "feel" to the brake pedals.

Of course, you are also entitled to your opinion, too...

Wow... is that necessary?
Most are installing springs to fix ?dragging brakes? rather than fix the underlying issue first. Your the first I have heard of that installed them to get ?greater tactile feel?. I would still recommend fixing the system before adding to it.
Perhaps it?s all my years flying antiques that had near zero ?tactile? feel, and near zero brakes :)
 
The early Cleveland master cylinders had an external spring but it was too weak from the factory so they issued a Service Bulletin to change them. They provided the parts free at the time. I changed mine but I don't think I had a problem to begin with.
When you set up the brake pedal linkage it is essential to make sure there is no binding as that will cause dragging brakes with any stock master cylinder springs, internal or external. There's nothing wrong with adding external springs but make sure your linkage is set up correctly first.
 
There's nothing wrong with adding external springs but make sure your linkage is set up correctly first.

There may even be additional benefit although I am no engineer. There are some really clean approaches to this like Tom?s that add bushings and the collar.
The master cylinders are intended to be actuated in a straight line. The geometry of the Vans pedals doesn?t do this, they put a side load on the shaft. ( per discussion with Matco). This side load wears the shaft and seal and they will eventually leak. (Mine did at about 600 hours.)
Perhaps the added spring with collar and bushings will help with the shaft side load issue? Perhaps not.
 
I am not a builder unfortunately. I'd like to one day. I just bought My RV8. Most fun ever imaginable and thank you for welcoming me into this very special group!

Today I had what I believe is the very issue I read in this tread... My landing went great and while taxing back to the hangar, I felt my right brake dragging. By the time I got to the hangar, it was smoking and crazy hot. Melted a half dollar size bubble in my paint. Bummer!

The brake is toast now. Nothing left. After it cooled, I tried a slow speed taxing and had nothing. No right turn capability. I had to shut down and walk her home.

My buddy Mike and I are going to dig into it tomorrow. Any advise one where to start (Once I dull the pants). I assume this spring and alignment thing is the culprit. Thank You!
 
Spring is different for the Cleveland 10-30 master cylinders! Check the free play on your springs!

The McMaster springs referenced so far in this thread are helper springs for the MATCO brakes. 9657K435 is a 3" free play spring which will only work on the MATCO. The MATCO spring will not work on the 10-30 Cleveland master cylinders (older RV's).

According to Cleveland (Parker) the external return springs, part# 082-14500, on the 10-30 master cylinders have the following specifications:
Free Play: 4.6" (4.55" minimum)
Outside Diameter: .552"
Spring Rate: 6.0 lbs/in minimum

I'm rebuilding my 10-30's and found the free play on my springs are 3.5", well under minimum! I suspect I have cheap springs that Vans used to supply, that don't hold their shape. If you are having return problems, check the free play. That might be your issue.

The Cleveland 082-14500 is difficult to find, and almost $40 each (2022)! Since I could not find a replacement I went to an aftermarket spring. McMaster did not have a spring that would meet the Cleveland spec.

A good solution is from compressionspring.com PC063-546-22800-SST-4563-C-N-IN. 4.563" free play, .546" ID, 8.359 lbs/in spring rate, 302 stainless steel. The specs are very close to the Cleveland, and they are stainless.

https://www.compressionspring.com/pc063-546-22800-sst-4563-c-n-in.html

$$
 
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I made my springs a little harder by stacking a few more washers on the top.

I will add though, on mine, I discovered lots of little friction at various points throughout the "system":

1. The friction between the "ears" of the brake pedals and the "ears" of the rudder pedals (I had lots of stiction from paint and grime, I used the 3m wheel to make both sides really smooth, so that the pedals easily nested into the rudder bars and had no drag. I think I might have tweaked the ears a hair also to give a better gap.

2. Non-aligned "ears". You basically have to have perfectly aligned 4 holes, all in the same plane, for there to be no friction in the stock plans. Doing the long bolt mod was a huge improvement in this, since it basically means the brake pedals themselves can swing free and you can't over tighten one side or the other. The long bolts are expensive, but you cut your hardware count in half.

3. Bad/wrong/old/etc o-rings. Use the correct mil spec o-rings when rebuilding. I had an o-ring box that was "close enough", except it wasn't. When I dug into the sizes, I discovered, that for example, you might decide to use a 1/4" generic o-ring to replace a MS28775-010. The trouble is, MS28775-010 is actually between 0.234 inches and 0.244 inches for the inside diameter. That 0.006 makes a big difference in the high pressure application of brakes. Ask me how my floor mats know...The mil spec o-rings also have a slightly taller profile than generic ones, which is just perceptible side-by-side, but impossible to see otherwise.

All those things together made my brake pedals swing completely free, without a hint of binding. Then, once reassembled and reinstalled in the plane, felt way better and I haven't had any issues with sticky brakes or leakage. Getting rid of all the stiction/friction points means the springs can actually do their job, and you might find you don't actually need harder springs.
 
All those things together made my brake pedals swing completely free, without a hint of binding. Then, once reassembled and reinstalled in the plane, felt way better and I haven't had any issues with sticky brakes or leakage. Getting rid of all the stiction/friction points means the springs can actually do their job, and you might find you don't actually need harder springs.

This is the basic design situation. If all friction is eliminated and it is ensured the master cylinders are indeed returning to uncover the fill hole, then the brakes will function without issue.

Full disclosure - - Initially as a novice builder, I did not fully appreciate how subtle friction affected the process and researched and purchased springs, collars and sleeves to remedy this so-called problem. Ultimately, (as mentioned) I did alignment of tabs, holes, paid attention to washers and clearances and the friction disappeared and got full return of the master plunger. It has been working nicely for years now.
 
I am not a builder, but I am an A&P. A friend of mine has an RV-8 and his plane was pulling left during taxi, and he had the Solid brake lines at the caliper, and I got him the braided flex lines from the guy that makes them up for RV's I forget his name. That helped a bit, but I think the brakes are still sticking because now it varies from right to left but not nearly as bad. His brakes have the small reservoirs attached to the actuators on the pedals. Are the springs in the above posts the same ones he needs? Also, I would like to rebuild his actuators and calipers and don't have a parts list source. Any part number help on this problem would be appreciated.
 
I am not a builder, but I am an A&P. A friend of mine has an RV-8 and his plane was pulling left during taxi, and he had the Solid brake lines at the caliper, and I got him the braided flex lines from the guy that makes them up for RV's I forget his name. That helped a bit, but I think the brakes are still sticking because now it varies from right to left but not nearly as bad. His brakes have the small reservoirs attached to the actuators on the pedals. Are the springs in the above posts the same ones he needs? Also, I would like to rebuild his actuators and calipers and don't have a parts list source. Any part number help on this problem would be appreciated.

There have been different master cylinders used on RV over time. Need to know what are used on the particular airplane to get the master cylinder rebuild kit or parts. Early kits used Cleveland 10-30 master cylinders and either a build kit or individual mil spec O-Rings could be purchased. The individual mil-spec O-Rings were a lot less than the Cleveland rebuild kits. Later kits came with Matco master cylinders and a rebuild kit could be purchased for around $20. There is one part that is a washer that has an O-Ring around the inside diameter that I have not been able to find separate that makes the rebuild kit worth while. Some builders also deleted the brakes and used Grove wheels, brakes, and master cylinders. Attached is the 10-30 Cleveland Master Cylinder Document.

Van's Aircraft sells a Cleveland and Matco rebuild kit. I have seen some RV-6(A) with dual brakes that used Cleveland on one side and Matco on the other. Aircraft Spruce also sells Matco rebuild kits but one needs to know which master cylinders were used in the build.

View attachment 10-30 Master Cylinder.pdf
 
That O ring washer you referred to is called a stato-seal and you can get them at Spruce but of course you need the part number. Those are used on the piper fuel sending units to help seal the screws. thanks for the info. I'll have to see if I can get some part numbers off those actuators.
 
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