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Old 03-06-2012, 07:16 PM
pauldan181 pauldan181 is offline
Join Date: Jan 2006
Posts: 208
Default Brake leak out

It was a perfect day for flying so I left work early, went to the hangar and found this....

Anybody have the MS # for the brake puck O-ring handy?

Paul Danclovic
Jamestown NC
RV-8A N181SB
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Old 03-06-2012, 07:32 PM
AltonD's Avatar
AltonD AltonD is offline
Join Date: Sep 2005
Location: Dothan, Alabama
Posts: 1,492

Been there, done that. The pads are worn out.
Alton DeWeese
N526RV RV7A Tip Up, IO360 180 W/Hartzel BA prop.
Flying ~950 hours since Aug 2010

Construction Log
?The secret of getting ahead is getting started. The secret of getting started is breaking your complex overwhelming tasks into small manageable tasks, and then starting on the first one.?

?Mark Twain
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Old 03-06-2012, 07:40 PM
bhester's Avatar
bhester bhester is offline
Join Date: Jan 2005
Location: Hopkinsville, KY
Posts: 1,037
Thumbs up O-Ring

MS28775-218 spruce pn=101-02300
Make sure it's not a crack in your brake line. If it is call Bonaco for braided steel lines.

RAPCO RA66-106-4K BRAKE LIN KT spruce pn=06-00651

If you have a Hand Rivet Squeezer get this:

Remember the pucks can be put in the wrong way and cause a bad day. Make sure they go back in like this, o-ring side goes in first.

Bobby Hester - Builder/Pilot/A&P
Surfing the web from Hopkinsville, KY
N857BH RV7A XP-O360 - Garmin G3X ADS-B IN/OUT 2020 Compliant
Web site:
Dec. 2020 VAF donator - alot better than any magazine subscription

Last edited by bhester : 03-06-2012 at 08:01 PM.
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Old 03-06-2012, 08:50 PM
pauldan181 pauldan181 is offline
Join Date: Jan 2006
Posts: 208

Thanks for the info guys, I've got some O-rings on the way.

I just replaced the brake pads a few monthe ago and the I'm going to make new lines from the brake up to the fuse even though the line was totally dry. It looks like the fluid was leaking out of the piston.

Paul Danclovic
Jamestown NC
RV-8A N181SB
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Old 03-06-2012, 10:15 PM
Bob Axsom Bob Axsom is offline
Join Date: Mar 2005
Posts: 5,685
Default This is unusual - not a normal wear problem

The fact that it is the left brake is unusual - it is the right brake that is often pushed during takeoff and wears prematurely when right rudder is applied.

Which piston are you talking about when you say it looks like it is coming from the piston? If it is the piston in the slave cylinder near the wheel the piston may have been installed backward (the company - Cleveland - even had a production run where pistons were installed backward and thay issued a service bulletin or AD for correction). The brakes work fine at first but as the pads wear down the O-ring comes clear of the cylinder enough to provide a leak path.

The O-ring sometimes comes from the factory damaged in assembly - I had one of those. This of course allows leakage.

I had a new master cylinders at the rudder pedals with weak return springs whick allowed fluid to come out of the top (back) of the master cylinder. Stretched the springs and reinstalled fixed that problem.

I had a new master cylinder with a factory assembly damaged O-ring which leaked fluid every time that brake was applied - deposited red brake fluid on the red carpet.

If your O-rings are the original equipment a MS O-ring with slightly different dimensions may have substituted for an AN O-ring which then leaks under pressure. Your leak does not appear to be a leak that only occurs under pressure.

If the cylinder walls are scarred the fluid could leak there.

I can not think of a leak involving the line unless it is cracked or broken at the flare, or the fitting is not properly installed or tightened.

Bob Axsom
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Old 09-12-2012, 08:31 AM
drmax drmax is offline
Join Date: Apr 2006
Location: Martinsville, IN
Posts: 470
Default me too

Hello and welcome me to the world of aircraft ownership! Just bought a 9A yesterday. My issue. Yesterday the right brake was leaking. He told me they had did the left brake 2 months ago. He said he should have done the right one at same time. He put in a new seal and away I went. 3 hrs later, (and a bit of a firm landing with some hot tires) parked and this morning, the left brake is leaking. Took off fairing and with a light, confirmed coming from up inside, and I'm assuming it's the oring. (same issue as yesterdays right brake puck) Pads are new.
Is this an on going issue with these? If I'm applying too much brake, is it going to leak...afterall, I'm on a shorter runway and I will be using the brakes. Please advise. I'm not about to go into the brake repair business.
Thx, DM
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Old 09-12-2012, 08:59 AM
flyeyes's Avatar
flyeyes flyeyes is offline
Join Date: Jan 2005
Posts: 804

Search the archives for "viton o-rings" and "83282"

This is a known issue with brakes, not just on the RV. Quick and easy fix.
James Freeman
RV-8 flying
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Old 09-12-2012, 09:05 AM
drmax drmax is offline
Join Date: Apr 2006
Location: Martinsville, IN
Posts: 470

Originally Posted by flyeyes View Post
Search the archives for "viton o-rings" and "83282"

This is a known issue with brakes, not just on the RV. Quick and easy fix.
i'll read/search later. For now, can you at least tell me that I need to order some parts? I want to get these underway. Er does these mean I gotta carry a brake kit with me, with a bleed kit? good grief
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Old 09-12-2012, 10:19 AM
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DanH DanH is offline
Join Date: Oct 2005
Location: 08A
Posts: 10,348

Short version...the supplied disk/caliper combination has a marginal kinetic energy rating for an aircraft with this speed and weight. Don't take my word for it; the calculation (from FAR 23.735) is simple. Repeated full stop landings on a very short strip do not allow time for the disks and calipers to cool.

Throw in some unintended brake dragging during taxi, or just too much brake steering and things get really hot. The stock nitrile o-ring has a rather low temperature rating, above which it gets charcoal-hard and useless. Brake fluid leaks out onto the hot disk inside the tight RV wheelpant. A leak while parked is merely an inconvenience. The flash point of standard MIL-H-5606 is low enough that more than one airplane has caught fire on the taxiway.

The suggested viton o-ring has a temperature rating about 175F higher than a nitrile o-ring. 83282 fluid has a flash point more than 200F higher than 5606 fluid.

Brake disks are a heat storage media. Disks with more mass store more energy at a lower overall temperature. The energy (heat) is released back into the air over time. Cleveland sells an upgrade kit with thicker disks. You don't absolutely need thicker disks, but they improve an A-model which is used in windy climates and/or subject to long taxi times.
Dan Horton
Barrett IO-390

Last edited by DanH : 09-12-2012 at 10:22 AM.
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Old 09-12-2012, 10:38 AM
aerhed aerhed is offline
Join Date: Dec 2008
Location: Big Sandy, WY
Posts: 2,567

Nice one Dan. You you must have had some good coffee this morning.
Actual repeat offender.
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