one break inop...other is fine

[N5ZX]

> Yesterday I went out to the hangar to run the engines for a few minutes.
>
> In the process of doing so, I discovered that my right break is inop.
>
> Absolutely nothing.
>
> Left side holds great....no problem at all.
>
> Right side is completely effortless....all the way to the stops....no
> resistance.
>
> There is no brake fluid on the ground.
>
> Nothing squirts or sprays when I press the pedal.
>
> The pedal returns to the upright position with no problem....which I
> think tells me the spring linkage is intact.
>
> And when I press on the pilot-side right pedal, I can see
> corresponding movement in the cop-pilot right pedal.....which I think
> tells me that the cross-linkage is intact.
>
> Again....left side break....perfect.
>
> Any thoughts?


Cole

[Roger]

Welcome to the world of Skymaster ownership Fuel guages, doors and brakes. I will never forget landing in Nassau and being rushed to turn off right to clear for a Delta arrival. Pushed both toes and immediately swung left, as the right was completely dead. So to make the right, I did a quick 270 to the left and pulled off.

You have to picture the Bahamian controllers voice that said "Man, what the hell was that" ?



The brakes are totally independant. The fluid is probably pooled in the belly. MIght need a new seal on the master.

[N5ZX]

Peachy.

Thanks for the insight.

I'll go look.

(see...I CAN make brief postings too)



Cole

[JeffAxel]

it turns out that Cessna mounted the right brake master cylinder higher than the left one. If the seals in your parking brake (located by the pilot's left knee) are bad, the right master cylinder can drain into the left one leaving you with no right brake. If there is no apparent leaking by the right master cylinder, but a lot of 5606 below the left one, the fix is to replace the "o" rings in the parking brake manifold. If there is leaking apparent at the right master cylinder, then I would start there first. Resealing the parking brake manifold is what solved this problem for me when I had it a few years back..........

[N5ZX]

Thanks, Jeff.
I'll double check the parking break.
My biggest head scratcher was that there was NO fluid anywhere.
Not under either master cylinder. Not on the floor panels. Not on the ground. None.
With the aid of a hangar-neighbor who happens to be an A&P and by even greater stroke of good fortune, has 15 years of experience rebuilding 337's, I topped off the Right Master (it was apparently about 2/3) empty.
Still no right break.
Our next move was to reverse-bleed the right break system.
10 minutes later...perfect right break.
So I had a problem. I found a solution (with the help of a lot of very nice folks ...THANK YOU ALL)
Now all I lack is figuring out the cause.
Break fluid doesnt evaporate so it had to go somewhere.
Since it isnt enywhere else...I gotta assume that the escaping fluid is pooled in the belly as suggested by Roger.
George Brown (my hangar neighbor) says that there is a swivel union where the gear rotates into the gear bay when retracted and that can weep fluid and make it "vanish".
Whereas I certainly have no data-points to argue against that possibility, I have difficulty imagining a "weeper" taking my break from good to gone seemingly overnight.
Needless to say....I'm racking up the hobbs time just driving around the taxi-ways waving at people as they gawk and greet me with the "What the heck is that?" look on the faces....which I am growing accustomed to...and LOVE IT.
Thanks again everyone.
Cole

[bking]

Just had the same problem occur and could not find a parts breakdown for the parking brake assembly in either the parts or service manuals. Do you by chance have the O ring part numbers you could share?

[Kim Geyer]

P/N should be MS28775-010 it takes 3 you can find the manual at Parker.com . You will also need O rings for to fittings ,you have to remove them to get the shaft out

[bking]

I'll past this info to my mechanic and thank you.

[B2C2]

I have the opposite problem. Left brake is soft. I looked at the left master and there is some evidence of leakage on the fittings leaving the cylinder. I have my mechanic looking at it tomorrow. My first thought was a leaky fitting that needs tightening and more fluid and bleeding to fix it. well see what he says tomorrow.

[bking]

Please let everyone know what you find.

[B2C2]

Well, there was no fluid in the master cylinder, so we topped that up and the brakes worked again. However when I taxied back to my hanger I discovered a line of fluid on the floor under the caliper location and sticky residue on the bottom of the caliper, so looks like the caliper seal needs to be replaced. They are working on it today. I think I managed to produce the fluid on the floor by sitting in the plane and pumping the brakes last weekend. I think its a pretty slow leak so no residue was there when I looked previously. I always look on the floor when doing a preflight for brake fluid so I'm sure it wasn't there before. Lesson being a slow enough leak at the caliper may not produce obvious leakage reside, as no braking is usually done in the hanger, but since the master cylinder reserve volume is pretty tiny, over time you can blow the fluid out and get no brakes.

[hharney]

If the brake pads get worn the caliper can exceed the limits of the seal and start to leak
This may have been the problem or maybe not

[B2C2]

well that's good to know. they are going to inspect the pads as well. They looked them over when I was there prior to disassembly and seemed to think there was time left on them but we'll see.

[cessnadriver]

Cole.
Just had the same situation with my SkyHawk-172. Came down to replacing the o-ring on the piston in the master cylinder. After replacing and bleeding the system the brakes works GREAT! Hope this helps.
BILLS