Grady

Got back to the ac today. After knocking the 2 bubbles out of the right MC yesterday and moving the rod, we turned our attention to the parking brake rigging. As I've said ALL calipers, MCs, parking brake, and braided lines were replaced. We checked the parking brake rigging and made adjustments. Turned out we didn't get full travel of the arm. we moved the module. THat little adjustment allowed more travel of the arm AND working parking brake. At 2600 RPM the brake held the AC....no movement. Proving also the pedal brakes now hold at 2700 rpm.. So problems solved. That trick of removing the MC pins, twisting the rod while tapping the cylinder isn't written in the service manual, but should be. Guys you may want to print this and place it in your books. I think most people don't get this involved with the ac. I like a challenge and this one was challenging and called for going outside of the box. I want thank those offered their thoughts and suggestions. So if you have soft pedals or your parking brake won't hold your ac at high RPM, you have a problem. Grady M20K

All seals and O rings were replaced on the MC, parking brake, and calipers. (Earlier text) MC rod was turned and pressed per your suggestion. MC was turned sideways and tapped. I think you can compress the internal MC spring more than 1/8th inch, at least on this one was 3/8s inch. How much brake fluid pressure should i push in the system? This is the pressure side of the brake system. Thank you again

Well I just spent 35 minutes telling what I had done and had the text lost in space. A summary I worked on the LH MC as you detailed. after much tapping and twisting no bubbles were seen. There was 13 PSI brake pressure applied through the caliper. We next cracked the brake line fitting and had some bubbles pass through the clear line, through the "T" and up the feed line. More tapping and rotating on the MC. No more air bubbles. next we put the pins back in and test the 'feel of the pedals'. I couldn't feel anything different. Gosh I wish I hadn't loss my first text....When we moved the MC rod there is some free play (3/8ths inch) an then its solid. When we bench tested the MC, there was no movement and the MC was solid. I'll try the same with the RH MC tomorrow. I have brakes, but what is the correct amount of stop? I pushed against the AC with the brakes applied and it doesn't move. period. I set the parking brake and pushed the plane. That's not right. Thanks for getting me going in the right direction. Grady

Planning on playing around with the cylinders tomorrow with an extra set of hands. There isn't much room or play in the area. Crossed fingers. Will report back. Thanks all.

I have a single system. And yes there must be air in the system. You cannot move the cylinders when the lines are connected at the ends. That includes turning them sideways. There is no allowance to do that. You cannot switch left and right cylinders. The cylinders were bench tested when rebuilt. They were installed with the cylinders full. No bubbles were observed in the lines at the cylinders, parking brake, or calipers. I've had a vaccum pump running for 22 hours without improvement. I'll think some more on your thoughts and try bleeding again. Thanks for your insight and findings. Grady

Linings are good, near new. The pedals are firm and not soft. I sat in a J model and found what solid feels like. What I'm thinking I still have a small amount of air in the system and have tried most of the methods prescribed to remove air. To include removing most panels for visual checks. Once again I have no leaks. The master cylinders were both rebuilt and bench tested. Their rod movement is 3/4 of an inch with pressure applied. It all sounds correct, but still has me baffled. Oh I can hold the ac up to 2400 rpm. It's something little.

As I said, master cylinders, calipers, parking brakes, were rebuilt. That means all new seals. The 156 stainless braided lines from the master cylinders were replaced. (Change of attitude)-The nose was raised 12 inches (nose high) and pressure bled from the from caliper and also from the back to the front. This work has been completed in the last 4 weeks using several gallons of new fluid. Oh there are no leaks. Presently running a vaccum pump on the system overnight. I'm conveyed all that's been done asking what have I missed? My test is, will the parking brake hold ac at 2500 rpm. I've talked with other owners and find that most have soft brakes and don't know it. My background: US Army aviation maintenance officer/test pilot with 33 years service. Mooney owner 26 years. Flying for 55 years.... Thanks for reading and your thoughts.

4 weeks of trying to bleed. Rebuilt master cylinders, calipers, park brakes, replaced as braided lines, and gone thru gallons of fluid. Bleed up and back. Pressure from the caliper nipples (15 psi) back through the system. Also raised the nose and bleed both ways. Currently have a vaccum pump running. What next? Oh it's a single station pedal brakes.