Is M20C brake bleeding possible?

[A64Pilot]

3 hours ago, M20Doc said:

I honestly can’t imagine that Mooney went through all of these gyrations to get the brake bled. Creating issues where none exist.

I think if you push the fluid out with enough volume and pressure, all the air comes out without any antics. I had zero issues with two rebuilt masters.  Took 15 maybe 20 min total

The best way to get rid of the jelly 5606 turns into is to not use it, decades ago the Military went to 23282, which is completely compatible but as a pure synthetic it doesn’t turn to goo, or become sticky, plus it’s pretty much fire proof if you happen to get a stuck brake, a brake fire with magnesium wheels under a fuel tank is not good.

https://www.aircraftspruce.com/catalog/lgpages/aeroshell08-14635.php

https://www.groveaircraft.com/fluid.html

83282 is slightly thicker in stupid cold like -65F so you should pre-heat, does anyone fly when it’s that cold? Where does it get down to those temps anyway?

In stupid cold use 87257 apparently, we never did in the Army though

https://www.radcoind.com/blog-post/a-brief-history-of-u-s-military-aviation-hydraulic-fluids/

[Kelpro999]

5 hours ago, M20Doc said:

I honestly can’t imagine that Mooney went through all of these gyrations to get the brake bled. Creating issues where none exist.

Agreed, I imagine an assembly line back filling and full stroking each system during the process then passing it along with perfect functioning results. The only reason I questioned the results I haven’t yet attempted is position of each master. Obviously it works or we all would need mad skills to exit mid field. Maybe bench bleed makes it stupid stiff and not desirable or no different. I’m just curious.

[A64Pilot]

You don’t bench bleed these, it’s not a car, even if you did how do you keep the fluid in with the ports mid way on the side?

Wouldn't hurt to try, just make a mess, but at least aircraft hyd fluid doesn’t eat up paint.

I’m convinced that fluid flowing through fast enough carries all of the air with it, dribble it through and the bubbles aren’t forced out.

[Alan Fox]

20 hours ago, A64Pilot said:

You don’t bench bleed these, it’s not a car, even if you did how do you keep the fluid in with the ports mid way on the side?

Wouldn't hurt to try, just make a mess, but at least aircraft hyd fluid doesn’t eat up paint.

I’m convinced that fluid flowing through fast enough carries all of the air with it, dribble it through and the bubbles aren’t forced out.

I was in the car buisness over 30 years , I NEVER bench bled mastercylinders ,  Removed the old master , installed the new master , filled it , had my helper step on the pedal 3 times , while I used my index finger as a valve over the hole , installed the lines loosely , watched the bubbles , when the bubbles stopped , tightened the lines , car was bled... Go figure , the master was the highest point in the system, and that magical force , you know , Gravity did the rest...

[RobertGary1]

On 11/28/2022 at 1:54 PM, M20Doc said:

I honestly can’t imagine that Mooney went through all of these gyrations to get the brake bled. Creating issues where none exist.

Not sure your shop but I know lake aero uses a recirc bleeder and I assumed that’s what Mooney did. 

[Kelpro999]

Update.

 Performed bench bleed in a test fixture and found hyd. oil binds with air much better than other fluids and for that reason bleeding above 10 fluid ounces p/min and one stroke p/sec x5 resulted in air free fluid when rolling upright or vertical. Less flow would leave some air trapped until lifting vertical about 5(mm3). 
Just a little almost worthless info if anyone was interested 

[47U]

1 hour ago, Kelpro999 said:

Just a little almost worthless info if anyone was interested

Soooo… success?  Firm brake application?

[Kelpro999]

6 hours ago, 47U said:

Soooo… success?  Firm brake application?

 Not exactly, just verified it can be done without too much trouble, still have the park brake & flap valves out.

 If hydraulic oil was anything like automotive brake fluid it would be much more difficult.