T

Tram

Well Known Member
Hey guys-

Just went out to the hangar and our floor has a nice puddle of brake fluid out of the right brake.

I pulled the pants off and noticed the caliber is obviously loose but could not find any direct location of the leak. I'm guessing a seal or something has gone..

What is the general direction of repair, if it is something like a seal?

Pull the unit off, throw a new seal in?

Thanks

Jeff
 
Tram said:
Hey guys-

Just went out to the hangar and our floor has a nice puddle of brake fluid out of the right brake.

I pulled the pants off and noticed the caliber is obviously loose but could not find any direct location of the leak. I'm guessing a seal or something has gone..

What is the general direction of repair, if it is something like a seal?

Pull the unit off, throw a new seal in?

Thanks

Jeff
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Two things:

1) Check the oring on the caliper.
2) Check the orientation of the caliper - it can be inserted backwards, if backwards it won't have enough margin before pressure can push the oring out.

I bet it is problem #2
 
Tubing failure

I had the same thing Tuesday evening. Went out to fly after work and there was a nice puddle. This makes 2 brake line leaks I have had. One about a year ago.

Same exact spot both times. It was were the aluminum tubing goes into the ferrel on the AN fitting where the top of the gear and bottom of the fuselage meet. It took over an hour to find it last time. It took 1 minute this time. Pull your upper fairing and check there.

In my case the fluid tracked down the outside of the tubing and at first it looked like the caliper was leaking.

All I can think of is the flexing of the gear over time caused metal fatigue and the tubing had a tiny split. Noticed the pedal just didn't feel right last time I flew.

Since this is twice, I went to a hydralic shop and had two hoses made. SS braid over teflon. Length from end to end is 33 inches (32 inches flare to flare). No loop at the bottom but it curves over very nicely to the caliper. Cost me 60 bucks for both hoses.
 
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Webb said:
I had the same thing Tuesday evening. Went out to fly after work and there was a nice puddle. This makes 2 brake line leaks I have had. One about a year ago.

Same exact spot both times. It was were the aluminum tubing goes into the ferrel on the AN fitting where the top of the gear and bottom of the fuselage meet. It took over an hour to find it last time. It took 1 minute this time. Pull your upper fairing and check there.

In my case the fluid tracked down the outside of the tubing and at first it looked like the caliper was leaking.

All I can think of is the flexing of the gear over time caused metal fatigue and the tubing had a tiny split. Noticed the pedal just didn't feel right last time I flew.

Since this is twice, I went to a hydralic shop and had two hoses made. SS braid over teflon. Length from end to end is 33 inches (32 inches flare to flare). No loop at the bottom but it curves over very nicely to the caliper. Cost me 60 bucks for both hoses.
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Had a cracked aluminum line where it goes into the brake about 2 years ago, I agree, the line probably gets brittle with flexing. Replaced it with one of Van's small flex lines used for oil or fuel pressure. No problem since.
 
There are several things that can cause this

When I installed my brake lines I uses a bulkhead fitting to connect the cockpit line to the aluminum line running down the strut with a service loop under the wing root closure faring and there is no problem at the top of the strut.

At the bottom I have the loop as Van specifies and that has worked fine.

Cleveland assembled sets of slave cylinders with the pucks in backward several years ago and there was a service bulletin on it as I recall. If you run the brake linings down enough the assembly reaches a point where fluid will seep past the O-ring on the piston (puck) and if they are backward it occurs much sooner because of the position of the O-ring grove (it is not centered on the piston).

The reason that it is always the right brake is it is consciously or unconsciously applied during the takeoff roll in conjunction with right rudder to keep the airplane on the runway. It wears much faster until the leak point is reached.

Especially with the "A" models it is something that has to be dealt with immediately. Been there done that twice and you can believe when I see any brake fluid I address the problem right now!

Bob Axsom
 
Overheat equals blown "o" ring

Had the caliper "o" ring go at least twice on the -8A due to overheating of brakes during long or cross-wind taxi. I have not had the problem recur since I installed helper springs on the outside of the master cylinders to ensure no dragging of the brakes.
 
I just had to deal with "the puddle" recently as well. As Bob mentioned above, mine was a brake pad that was allowed to get too thin, allowing the piston to travel too far, thus exposing the o-ring and allowing the fluid loss. Turned out the o-ring was old and flattened as well, so I ended up putting new o-rings and pads on both sides, for good measure. All FWIW!

Good luck, hope its a simple fix!

Cheers,
Bob
 
Well, I was able to spend some time tinkering on the plane..

I pulled the pants off and got the caliper off. The right side is toast. Needs new pads and also looks like I may need a new o-ring. I couldn't find a direct obvious source of the leak.

I'm just curious, after I pulled the caliper off, I compressed the piston. What is the best way to get the piston uncompressed so that I can attempt to change the o-ring?
 
Tram said:
.......I'm just curious, after I pulled the caliper off, I compressed the piston. What is the best way to get the piston uncompressed so that I can attempt to change the o-ring?
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Just step on the brake pedal, and that lil' sucker will blow right outta there! Then ALL the brake fluid including what's in the reservoir will drain out on the floor. :p

OR, get a helper and gently push on the pedal until the piston begins to appear, then stop and remove the brake line from the caliper and cap it off, trapping the fluid in the line and reservoir. Then pull the piston out by hand.

And while you're at it, why not do both brakes? Then no more worries. New pads and O-rings, cheap insurance.
 
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PCHunt said:
Just step on the brake pedal, and that lil' sucker will blow right outta there! Then ALL the brake fluid including what's in the reservoir will drain out on the floor. :p
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The caliper is sitting in the floor next to me.. There is no fluid in it nor the reservoir..

It's all already leaked into the floor.. ;)

PCHunt said:
And while you're at it, why not do both brakes? Then no more worries. New pads and O-rings, cheap insurance.
Click to expand...

I am.. :)
 
Try a LITTLE bit of air pressure in the brake line fitting on the caliper. Be sure the piston won't shoot out and go across the shop! Put the caliper face down on the bench as you do this. Start with low air pressure and work up. Wear face protection. YMMV for this $0.02.
 
PCHunt said:
Try a LITTLE bit of air pressure in the brake line fitting on the caliper. Be sure the piston won't shoot out and go across the shop! Put the caliper face down on the bench as you do this. Start with low air pressure and work up. Wear face protection. YMMV for this $0.02.
Click to expand...

Like he said, a little pressure is all it should take. Out on the ramp at Nellis, the air pressure came from...yours truly. Be advised, brake fluid no taste good :rolleyes:. Next time a little baggie over the fitting, with a hole in the end will make it a better operation (as will changing pads more often! ;))

Cheers,
Bob
 
It is more than likely the O-ring. I blew one out at Osh in '09 taxiing through the mud. The brake gets heated up and deforms the o-ring. It will probably look flat instead of round. Easy fix.
 
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