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Old 10-06-2017, 06:14 PM   #1
Coopere
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Default Aztec hydraulic leak Parking brake valve

Seems my Aztec is mad at me for not flying it in the past 28 days... due to finishing off my instructor rating...

Fluid after a flight last week found running from the belly seam (forward seam of the removable belly pan) Clean ish fluid on the pilots side however their is a much older contaminated streak on the co-pilots side as well

the clean ish fluid is 5606 for sure, the other is more yellow than red but has a slight red tinge... I did have the airplane corrosion x'ed a month ago on my last flight so I believe the yellow / red fluid is simply fluid that has migrated over and mixed with the corrosion x

did some looking around today with my scope, and the parking brake valve has a rather large clean droplet of 5606 on the bottom aft fitting and the valve itself is oily so I suspect it has been leaking for some time

is there any other places I should be looking to find leaks in this area?

I took a good look at the nose gear actuator, all gear fittings to the front of the cabin firewall, gear priority valve, co2 shuttle valve and gear door actuators none of these components show signs of leaking

also looked in the cabin at the tops of the brake master cylinders no leaks observed but due to the carpet and floor I can't see whats down under the floor

thanks
Eric


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Old 10-07-2017, 01:04 PM   #2
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I had that problem a while ago. It is a simple o-ring fix, but getting to them for removal and installation is a pain. The heater is in the way. I was able to get to them by removing the heater control cables from the heater. I also had plugs for the bake lines to simplify the bleeding process after installation.

Any leaks from the master cylinders will show on the top of the cylinder or the hose attachment fittings, the rest of the body is solid.


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Old 10-07-2017, 04:30 PM   #3
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thanks Jim for the insight ill mention to my shop to plug the brake lines as well
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Old 10-08-2017, 04:50 PM   #4
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If they are good they can avoid having to bleed the brakes by letting fluid run from the reservoir and through the valve and then hooking up the hose to the master cylinder while the fluid is still running. A little messy, but easier to clean up than bleeding.
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Old 10-14-2017, 02:04 AM   #5
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So attempted to fix the parking brake valves today, they are Hoof A 77 valves, we were able to source the o-rings for the plunger shaft however their is what seems to be a packing o-ring under the brass nut on the base of the valve (when mounted in the aircraft the nut is on the bottom of the aluminium valve body) this o-ring seems to be semi circular, flat on the bottom and round on the top (half moon)
we can't find a single part number for it in my parts manual, called our local piper dealer and no luck, response was "purchase a removed serviceable valve" - same model likely not overhauled and likely could leak and be the same issue I have now

piper has no superseded valves, just discontinued

I understand hoof is long out of business...

my shop suggested purchasing 2 new valves from Scott, the 4500-a1 valves and replace the hoof with the Scott... seems excessive to purchase a $200 valve for the sake of a $5 o-ring... being generous

but at the same time if the o-ring is not available and in finite decreasing quantity I would not object to purchasing 2 new production similar type of valves...

thoughts?
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Old 10-14-2017, 12:59 PM   #6
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On mine they were the same o-ring. AN6227-5
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Old 10-14-2017, 01:11 PM   #7
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The Scott valves are widely available in good condition. They are directly interchangeable with the Hoof valves.

http://www.ebay.com/itm/Scott-Valve-...5ZgdgT&vxp=mtr
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Old 10-14-2017, 08:45 PM   #8
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thanks guys for the solutions!
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Old 10-14-2017, 09:48 PM   #9
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Jim, An6227-5 crosses to ms28775-010. this unfortunately isn't the o-ring I need, already have those in stock and are way too small

its the one under the brass nut on the bottom of the valve, I think ill just order the newer Scott valves, the ones Phil has suggested


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