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Taxiing out for takeoff the Pilot side right brake began to get soft and completely failed before takeoff. I jumped into the right seat and found I had good brakes. I taxied back to the hangar. By the time I parked the plane, the Co-pilot side right brake completely failed too.
I found after inspection… The ONLY fluid leak was from the Pilot Side Left pedal reservoir vent cap.
Can anyone explain this?
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The right and left systems in most or our planes are independent of each other except the later 4-place that had the new parking brake.
The right side needs to be checked. If no leaks near the caliper then I would start by repumping the system back up (we have a video on that).
Clean the fluid off the left side and then watch for releaks.
Cheers
Roscoe
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Roscoe is correct. I had the same problem with my right brake and after pumping it up 3 times with the same failure it ended up being the right brake master cylinder. There are 2 O-rings that are in the plunger inside the master cylinder and the inner O-ring (smallest one) was disintegrated. We rebuilt both of them since we were down there anyway. Thanks to Roscoe for all the videos and to Rags my IA out in chandler for all the expert advise and know how.
Lon -
I decided to go ahead and pull all four brake cylinders off and overhaul them. We did find two of the small O-rings were not correctly sized from the last guy that overhauled them and we found one O-ring that was hardened. After bleeding the new system, all seems to check good. I still can’t understand how right brake failures on both sides ended up with the only trace of fluid coming from the Left Master Cylinder. Maybe the parking brake will be next…
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Well… Overhauled all four brake cylinders. Added new brake fluid. Test flight and once again found that fluid is being pissed out the Left Master vent cap. I’m totally confused now. The only thing left is the Hydraulic parking brake. I just ordered the O-rings for that. If this is the problem, then fluid is passing from one side to the other.
Has anyone ever seen this?
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I finally resolved the problem! This is good info to know if you have a hydraulic parking brake. I think they came along in 1978 and later models.
The parking brake has 5 O-rings. FLetch-Air has them. The brake is designed as a cam shaft that rotates two pushrods pushing springs and heads up and down for the Left and Right brake lines, locking pressure into the brake lines when engaged. The brake is divided into two sides by an O-ring in the middle of the cam shaft. This O-ring prevents fluid from traveling from Left to Right and visa versa.
Here’s what caused my brake failure. That Center O-Ring was warn to a point where fluid was being pushed from the Right Brake lines into the Left. Thus draining the Right Side fluid into the Left reservoir and overflowing the Left reservoir through the vent cap on top and onto the cockpit floor. Eventually I had exhausted all fluid from the Right brake lines and lost all Right braking ability in both pilot seats.Hope this helps anyone with similar brake problems. Don’t hesitate to contact me if you need help.
-wc
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