Bleeding dual brake systems

[Buckblaster]

Looking for tips on bleeding dual brake system. My 75 M20F has 4 master cylinders, I repacked all 4, blew brake lines from master cylinders to calipers out with shop air, wanted a clean start. Reinstall master cylinders, hooked up pressure pot (max 15 psi, i did not carbonate fluid, been using pressure pot very long time…) and as per manual depressed the pedals I wanted to bleed. Worked fine on pilots side. Manual say to depress CP pedals to sequence shuttle valve,,,, so I depressed CP pedals and bled both sides again, nothing… dead pedals on CP side, GTG on pilots side. I tried it with about a gallon of fluid. I believe there is an issue with my shuttle valve. I didn’t see it as I removed every belly panel (location?). Help please…

 

thanks,

Paul

[Fly Boomer]

9 hours ago, Buckblaster said:

Looking for tips on bleeding dual brake system. My 75 M20F has 4 master cylinders, I repacked all 4, blew brake lines from master cylinders to calipers out with shop air, wanted a clean start. Reinstall master cylinders, hooked up pressure pot (max 15 psi, i did not carbonate fluid, been using pressure pot very long time…) and as per manual depressed the pedals I wanted to bleed. Worked fine on pilots side. Manual say to depress CP pedals to sequence shuttle valve,,,, so I depressed CP pedals and bled both sides again, nothing… dead pedals on CP side, GTG on pilots side. I tried it with about a gallon of fluid. I believe there is an issue with my shuttle valve. I didn’t see it as I removed every belly panel (location?). Help please…

 

thanks,

Paul

I don't have any suggestions, but I have read several topics here on bleeding.  If you want to try to track those down, try using the search engine in your favorite browser.  You can restrict a search to a single website like this:  site:mooneyspace.com x y

It will search for x and y, but only on mooneyspace.com.  The search function using the forum search engine is pretty weak, and it's amazing how quickly my browser's search engine spider has crawled mooneyspace and picked up new topics and new posts within topics.

[M20F-1968]

Fow what it is worth, I installed the co-pilot brakes in my plane when I did the rebuild.  Bill Whaet pointed me to a schematic that Mooney had that did not have a shuttle valve.  I used that arrangement.  He advised against the shuttle valve.  You might look at a different configuration of the hydraulic lines.

I have had no problem at all with the configuration he recommended.

John Breda

[BillyT0020]

Not sure if you’re still dealing with this issue but I FINALLY got my brake system after working on it for days, albeit a single sided system .

I replaced the Master Cylinders, one of the hard lines coming of the MC (flare snapped off during install and had to run 4’ of 1/4” OD new aluminum to the next union), pads, rotors, rebuilt the calipers, checked all AN fittings, and blew air through all the lines.
 

After ALL thats I couldn’t get them to bleed. I tried all the normal methods, bottom up, pumping brakes while opening the bleeder valve and filling the reservoir, tapping lines with screwdriver, lifting the nose etc. The only thing that worked is capping off the vent with a caliper bleeder valve, filling up the reservoir, them pressurizing the fill hole with 80 psi of air. Luckily a normal tire air valve threads into the reservoir and the caliper bleeder valve works perfect to relieve the pressure after you’re done. Without capping the vent with the bleeder valve, the air couldn’t push the bubbles out of the system for me.
 

Pic of the final set up that did the trick for anyone else struggling to get the air out of the system. Wish I would have tried it sooner, literally was done in 10 seconds after I hooked up the air. 
 

Billy