Van's Air Force
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Rebuild Brake Cylinder- Leaky one or both?
- Thread starter Beejer
- Start date
[email protected]
Well Known Member
I did both…
After about 2700 hours my right master cylinder was leaking noticeably… Decided to do both while I was there as a general preventive maintenance task. Pretty easy decision when the kits are only $35 ;-)
After about 2700 hours my right master cylinder was leaking noticeably… Decided to do both while I was there as a general preventive maintenance task. Pretty easy decision when the kits are only $35 ;-)
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cvairwerks
Well Known Member
If you are in there for the one, might as well do the other. Most cylinders are located where it's pretty awkward to get to and you would probably rather fight the battle once to get them out and back in. Doesn't take much more time to rebuild the second and bleed that brake over the first.
henrysamson
Member
I had one leaking and have brakes for both seats of my Kitfox. I did them all. The first one took over an hour and the second about half an hour and the last two 15 minutes each. I'd do both. The parts were not that expensive.
Henry
Henry
rocketbob
Well Known Member
Van's brake cylinder mounting designs have a lot to be desired. As a result of the shaft and body get sideloaded due to mounting sloppiness and the shaft scratches the top cap. The orings then get shavings embedded and start leaking. As others point out polishing parts on a lathe when rebuilding is required. Its the poor mounting design that causes them to leak.
[email protected]
Well Known Member
Plus 2 or maybe 6 on do them both when you are under there and have to bleed them anyway
Fixit
Fixit
Scotchbrite worked on mine to remove the aluminum that had built up the first time and then I refined the position to minimize the side load. Have not had to do much other than replace o-rings since refining the position to minimize the side load. The new piston shafts are still sitting in my parts bin after 20-years. I was sure that the side load was going to require replacement of both shafts but lucked out getting the sideload removed.
SL-00047 Brake Caliper O-Ring Improvement.
While in there it might not hurt to do this at the same time. It will be the next thing to leak.
SL-00047 Brake Caliper O-Ring Improvement.
I did mine this spring at the same time I replaced the brake cylinder seals that were leaking.
It doesn't take that much longer to do and your having to bleed the brakes anyway.
While in there it might not hurt to do this at the same time. It will be the next thing to leak.
SL-00047 Brake Caliper O-Ring Improvement.
I did mine this spring at the same time I replaced the brake cylinder seals that were leaking.
It doesn't take that much longer to do and your having to bleed the brakes anyway.
JonJay
Well Known Member
Hey Gary - how did you improve the geometry?
I’ve been voicing Rocketbobs comments for years, but have never seen anyone engineer a solution.
I took the time with spacers & some washers so as to minimize the side load. There is still some slop but the push from top to bottom is as perfect as it can get without a clevis.
My RV6A has Cleveland master cylinders, and I also have the floor mounted rudder pedals. I noticed that the entire rudder pedal assembly can be pushed left and right, about 1/4 inch of movement. Does anybody have that on theirs also? I'm wondering if that is by design, or if my resin end caps need some filler material added to stop this slop.
I ask because this means any attempt I make to eliminate the side loading of the master cylinders with spacers is pointless, if the entire rudder pedal assembly can shift.
My master cylinders are leaking like crazy. The reservoir emptied itself onto the floor over a 2 week span. They were previously mounted on the bolts pretty firm, although I can't prove that's the cause of the leak. I'll be rebuilding them today. The attachment bolts at top and bottom have castle nuts and cotter pins, so I'll be keeping them intentionally loose to minimize the side loading, unless I find a better solution.
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Tracer 10
Well Known Member
To all rebuilders of brake master cylinders.
During disassemble lay all the parts out on clean shop towels in the exact order they came out. Clean, inspect as needed. There are some pretty small O-Rings & parts in this repair kit. Be very careful when removing old O-Rings not to score any metal parts by using a sharp pick (be careful). Larger O-Rings can be removed with just your fingers by pinching them enough to get a toothpick under them to help removal. Look up the diagram on the internet site & enlarge it to understand what you are replacing. During reassembly lubricant everything with hydraulic fluid. That website is on the instructions. Bleed the brakes from the wheel cylinders up thru the master cylinders to the reservoirs.
During disassemble lay all the parts out on clean shop towels in the exact order they came out. Clean, inspect as needed. There are some pretty small O-Rings & parts in this repair kit. Be very careful when removing old O-Rings not to score any metal parts by using a sharp pick (be careful). Larger O-Rings can be removed with just your fingers by pinching them enough to get a toothpick under them to help removal. Look up the diagram on the internet site & enlarge it to understand what you are replacing. During reassembly lubricant everything with hydraulic fluid. That website is on the instructions. Bleed the brakes from the wheel cylinders up thru the master cylinders to the reservoirs.
Remember back in the old days when we had to rebuild the mastercylinders and wheel cylinders on our cars? Brush Research came out with the ball flex hones and they are fabulous. They dont remove any appreciable material, but do lay a perfect crosshatch pattern to allow the piston seals to actually seal.
They are readily available. Sometimes just changing seals that ride against a really smooth bore wont seal all the way. And--if the master cylinder piston has alittle side load, the bore 'could' wear in a slightly tapered pattern. WE found that years ago especially with aluminum master cylinders became more prevalent in the later 70's in the automotive industry.
So if you have a troublesome sealing issue, try this. Beats buying a new cylinder.
Tom
They are readily available. Sometimes just changing seals that ride against a really smooth bore wont seal all the way. And--if the master cylinder piston has alittle side load, the bore 'could' wear in a slightly tapered pattern. WE found that years ago especially with aluminum master cylinders became more prevalent in the later 70's in the automotive industry.
So if you have a troublesome sealing issue, try this. Beats buying a new cylinder.
Tom
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