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RV7A Brake O Ring Replacement

Tcheairs

Well Known Member
Need to replace the O rings on my Cleveland brakes. The caliphers have a number 6 embossed on them followed by an embossed K 90. Can anyone lead me to the proper parts needed (O rings + anything else)? Also, if there is a YouTube video available or other description of the process I'd appreciate a link to that as well.

As complete a set of systems manuals I have, the builder neglected to include anything on the brakes..

Thanks
 
Try these.

https://store.vansaircraft.com/u-00015-1.html

As for replacement, just pressurize the brake assembly with a little shop air and the piston should pop right out. Work the o-ring off with an awl, small screwdriver -- don't gouge the channel. Apply a little brake fluid to the new O-ring and slip it into place. Line up the piston into the cavity and press into place.

McMaster Carr has them too -- https://www.mcmaster.com/1288N178
 
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RV 7A O Ring Seal

Found the part number in the Vans Store catalogue..U-00015-1. However they are out of stock and backordered..Is the McMaster-Carr part you attached the same? Thanks for the prompt reply..

Tcheairs
 
Found the part number in the Vans Store catalogue..U-00015-1. However they are out of stock and backordered..Is the McMaster-Carr part you attached the same? Thanks for the prompt reply..

Tcheairs

Same materials, dimensions, spec #'s, etc.
 
Bleed the brakes

You will also need to bleed the brake system of air. Most do it from the bottom-up on RVs. You can find several threads on VAF on how to do this.
 
Brake bleeding

Bleed from the brake caliper up; and the brake fluid will go thru the master cylinders to the reservoir at the top. Search bleeding brakes on this forum to save yourself making a mess.
 
Replacing pads and no bleeding the system.

I have done this on my RV6A and it works...

Plug off the brake line as soon as you disconnect it. Plugs and caps can be found at Aircraft Spruce. You can also use brass fittings from hardware store. You are only going to install finger tight 45 to 37 deg. no problem.

Before you press the piston (with the new "O" ring) back into the caliper, pour some brake fluid into the cylinder about 1/2 full. With the fitting capped (on the caliper) press in the piston, head first. Once the O ring is seated in the cylinder, turn the cylinder with the piston skirt down on the bench. Loosen the cap and gently push down on the caliper. Have a cup under to catch the expelled fluid. When the piston is flush with the caliper surface, and fluid was pushed out, there is no air in the caliper so tighten the cap by hand.

Install the caliper on the wheel with the pad plate. At this point, make sure your brake fluid reservoir is 80% full. Remove the cap from the caliper. As you remove the cap from the brake line, it is going to start leaking... as it is leaking, air will not get in..... connect it to the caliper and tighten.

Complete the brake install. Check fluid level. Gently press the brake pedal for that wheel till it stops, to seat the pads. Release and press again. If brakes are firm, YOU ARE DONE. If they are spongy, then proceed with bleeding procedure. I have had very good luck with this procedure.
 
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So, what about the master cylinders? Do they need to be bled also?

Yes. And under normal procedures, the only air in the system is in the master cyl's, and that air is pushed all the way through the system until it comes out the reservoir.

My procedure described above, eliminates all of the air in the cyl's... and if not, there is very little left to bleed out.
 
You might consider switching to Viton O-rings. Same size, just higher temperature tolerance, and compatible with just about any fluid.

At the same time, drain your brake system and re-fill it with Royco-782, the higher temperature Mil-PRF-83282 hydraulic fluid.

This change (to both the o-ring and the fluid) goes a long way to making a brake fire nearly impossible.

Also, PLEASE pay attention to which side of the puck goes into the caliper. The face with the longer distance to the O-ring goes out. If you turn it around inadvertently, (so that the shorter side is out) it is possible to have the puck pop out when the brake pads are worn down to near the minimum.
 
GLT V1038 compound

It seems the Viton orings from McMaster are not the GLT (good for low temperature) V1038 compound while the Van’s are.

Size is AS568-218 for the Cleveland calipers I am familiar with on RVs.

Ref description in the Van’s store for PN U-00015-1 as well as SL-00047.

Standard Viton compound gets remarkably hard at low temperatures. We used Viton in gasoline fuel injectors when I was in that design world in the 1990s because it’s good at high temperature. They would seep at the required low temperature test -40F but when the engine started they would stop leaking and be undamaged, static seal application, dynamic seals on brake pistons are more challenging. We changed to a GLT compound. Brakes are going to be cold when you need them.
.
 
Puck reinstallation

Like Steve Smith said above:
Just make sure the puck is reinstalled correctly. It can go in the right way and the wrong way. If it go back in the wrong way you will end up loosing all your brake fluid one day and your brake will fail. O-ring side goes in first. Here is a picture that shows the right way to reinstall it.

1173CD9D-96AF-4C6F-8FDB-9359B140AEAD.jpeg
 
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Does anyone know if the Viton O-rings are available for the Matco -7/A brakes?

I ordered the U-00015-1 O rings and they are about 25% too small.

PS- I have a pack of 4 for the U-00015-1 O-rings if anybody needs them.
 
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Does anyone know if the Viton O-rings are available for the Matco -7/A brakes?

I ordered the U-00015-1 O rings and they are about 25% too small.

PS- I have a pack of 4 for the U-00015-1 O-rings if anybody needs them.

I have 4 orders from Vans.. they seem to be back ordered.. I’ll buy them off ya!
 
Does anyone know if the Viton O-rings are available for the Matco -7/A brakes?...

Those are size AS568-222. You could get them from McMaster for instance, 75 durometer is what you want, but they won't be the GLT (good for low temperature) V1038 compound.

Better to get the GLT ones from Van's, PN U-00025, never mind the store says it's an RV-14 part. They're cheaper than McMaster because you don't have to buy 25 ea.

BTW Van's also has the size -224 GLT oring for RV-10 calipers, be they Cleveland or Grove, Van's PN U-00026.

Ref also my post here.
.
 
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Thanks for the response John. I've already ordered from McMaster. It would be nice if Vans would cross reference the substitute numbers, but I've heard that they're sold out of almost everything anyway. Fast shipping from McMaster.
 
https://store.vansaircraft.com/u-00015-1.html

As for replacement, just pressurize the brake assembly with a little shop air and the piston should pop right out. Work the o-ring off with an awl, small screwdriver -- don't gouge the channel. Apply a little brake fluid to the new O-ring and slip it into place. Line up the piston into the cavity and press into place.

McMaster Carr has them too -- https://www.mcmaster.com/1288N178

be extremely careful if you choose to use shop air to get the piston out... it can get exciting.
 
ACE

I needed a brake puck o-ring right away once and got one, (along with a couple spares), from ACE Hardware. Worked like a champ. In the meantime I ordered some from Vans.
 
We released a service letter this past August, SL-00047, which covers the Viton O-rings we sell and which original O-ring parts they replace.

The service letter also includes the basic O-ring dimensions for each. Even more detailed information is available for each of the three O-ring models on the Van's web store.

Hopefully, that will be useful info for people who are trying to cross reference or replace.

And it appears that, as of the time I am posting this, the U-00015-1 O-rings are out of stock. I'll see what info I can get about availability tomorrow.​
 
What about the master cylinders?

Thanks all. SL-00047 acknowledged and new caliper o-rings ordered but no mention of the master cylinders. Are those o-rings fine with MIL-PRF-83282? Just want to check before I fill my RV-7 up with Aeroshell 31!
 
What about the master cylinders? SL-00047 acknowledged and new caliper o-rings ordered but no mention of the master cylinders. Are those o-rings fine with MIL-PRF-83282? Just want to check before I fill my RV-7 up with Aeroshell 31!
Wondering the same thing.

Are there seals/o-rings in the MC's that should be swapped when switching from 5606 to MIL-PRF-83282?
 
Does not require any seal changes. 5606 and MIL-PRF-83282 are compatible and interchangeable. If your system works with 5606, it will work with 83282.

Attached is the MIL-PRF-83282 spec as a reference.

View attachment 40040


Thanks very much.

I guess there's a low likelihood of temperatures rising very high upstream all the way to the MC's, even if a caliper were to stick (for example) and therefore no need to worry about MC seals that can withstand the higher temperatures that 83282 can endure?
 
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