The brake on the Velocity seem to cause everyone heart ache. We got rid of our parking brake a while back because it made it even harder. The new Cleveland brake system has 2 master cylinders on each side of the airplane, run in series, which run to a common reservoir. This is convenient from a fill standpoint, but complicates bleeding as the air bubbles like to run from this-side-to-that at the slightest provocation. I hate brake bleeding.

Over the winter I had a minor leak on the copilot brake line. It left some air in the line that I needed to get out. I tried pressure bleeding. I tried vacuum bleeding. I tried doing each to each side of the airplane in turn. Nothing really was successful. For pressure bleeding I resorted to something likeĀ this, where I pulled the hose off and replaced with the tygon the size of the brake nipple (1/8″ maybe? I forget).

After quite a bit of fiddlefarting around, here is the process that seems to have generated good results for me.

  1. Buy a “real” bleeder, like theĀ MityVac
  2. Fill the brake revervoir
  3. Pump up each brake, crack the bleeder at the caliper to remove any air at the caliper
  4. Refill reservoir about 1/2 to 3/4 full
  5. Apply light (~10″) vacuum with the MityVac on the reservoir
  6. Have 2 folks get into cockpit and simultaneously pump up both brakes on both sides of the cockpit. This seems to (empirically) pump up the pressure downstream of the cylinders and (while pumping) allow any entrained air to move from the pressure side towards the reservoir.

My theory might be wrong, but this process did give me the best brakes I’ve had in a year, where I can easily do a full power run-up with no trouble holding the airplane still.

MityVac Bleeder

Use low vacuum to make sure air doesn’t leak in around master cylinder seals

Pressure Bleeding

Vacuum on reservoir – if you look closely at the larger version you can see air bubbles forming on the surface of the liquid as they’re sucked free


Posted By: Brett Ferrell
Monday April 25th, 2016 at 9:57 PM

Categories: Maintenance
Tags: Bleeding Brakes Maintenance

One response to “More Brake Bleeding”

  1. Document says:

    […] out this maintenance article on brake […]

Please Login to Comment.