Bleeding Brakes

[@FreedomFlight1]

very helpful thanks

[@peterlastrucci324]

I always change out the nitrile or Buna caliper "O" rings and fit viton. They have a much higher temperature tolerance and are far less susceptible to leaking brake fluid on to the hot disc with associated fire risk . Using a synthetic fluid like 782 is also good.. I

[@3dogman311]

About to do this on my RV14A & I am now puzzled about bleeding the "master cylinders". I thought the process was to simply start at the caliper of each wheel, fill that line to the single firewall reservoir & only fill the reservoir slightly less than halfway. That leaves room to bleed the second brake. In the end with both lines filled & bled the reservoir should be about 2/3 to 7/8 full. I'm I on the right track..?

[@baselegaviation1614]

you are correct. That will work just fine.

[@cessnatpa]

I just bleed the brakes on my RV12 for the first time and had a hell of a time getting air bubbles past the master cylinders. Any tips or tricks for those style systems?

[@davidheal4623]

On the RV-12 make sure that the individual master cylinders are in the fully extended position (i.e., brakes fully OFF) when you bleed the brakes.

[@baselegaviation1614]

as mentioned, make sure the pedals are fully back. If they stick, loosen the bolts. You may have to add washers to the bolts to line the pedals up straight between top and bottom mounting bolts to ensure there is no sideways pressure.

[@gavinconnolly699]

My RV-4 has the master cylinders mounted ‘inverted’ - it’s an option in the drawings and keeps the bulk of the cylinder and hoses out of the way. However it means you have to bleed them car style - top down, otherwise it’s impossible to clear the bubbles form the master cylinders. Took me way too long to work out that it’s impossible to bleed from the calliper with that set up.

[@firstielasty1162]

Wow...that single shear...cantilevered bolt lower master cylinder mount is very sketchy. Strange that the upper attachment looks stout, and is double shear, but they have the exact same force applied to them.

[@baselegaviation1614]

it works just fine. unlike an airplane, the brakes in the helicopter are hardly used, and with not much pressure applied. basically used at rotor engagement.