66 m20 c brake problem

[av8or99]

Help. Brakes only work if you snap them quickly. If you slowly depress them they go to floor. So had mechanic rebuild them still same problem. Don't know what to try next. I am a new mooney owner. Thank. AP

[Fly Boomer]

2 minutes ago, av8or99 said:

Help. Brakes only work if you snap them quickly. If you slowly depress them they go to floor. So had mechanic rebuild them still same problem. Don't know what to try next. I am a new mooney owner. Thank. AP

I would try a different mechanic.

[Rwsavory]

You may need to have the shop bleed the system again. We had new brake lines put on our plane some years ago, and it took repeated efforts to get all the air bubbles out.

[Utah20Gflyer]

When you say the mechanic rebuilt the brakes do you mean he redid everything in the brake system or did he just do the master cylinders?  Pads? Rotors? Brake fluid reservoir?  Etc.  It might help to know what was actually done. 

The comments about bleeding the brakes is on point.  That could very well be the issue. 

[Ragsf15e]

There are some homegrown techniques for bleeding the brake lines….

[MB65E]

The old master cylinders can be really tricky. There is a thin metal washer/spring that develops cracks and looses tension. I rebuilt mine 2x prior to finding the crack. You cant even see it until some one tell’s you “I bet your spring is cracked.” 
I would be highly surprised if a shop found the issue. 
This gentleman listed below was a pleasure to work with and sells rebuilt master cylinders with new washers and orings. 

Bill Goerschel is his name. 
+1 (507) 581-9761
carolannegoetschel@yahoo.com

 

-Matt

[av8or99]

Matt you are the winner. Took them both back apart and you are correct the spring washer has no spring left and broke in half in my fingers. Thanks for that. Now I have to find where to source that little spring washer. I am surprised that it didn't come in the rebuild kit. Thanks for you input.

[MB65E]

I couldn’t find them on my own. However bill has them.

glad I could help,

-Matt

[av8or99]

I think I found the right part at McMaster. Thanks again for your input. 

[hammdo]

Link to part would be nice....

-Don

[av8or99]

https://www.mcmaster.com/9715K18/

[Don Gates]

I built a makeshift pressure pot bleeder out of a garden sprayer, though the fancy Aircraft Spruce ones are better. It took several bleeding sessions to get all the air out.  Lots of establishing the “bottom up” flow then pumping the brake pedals.  Also cycling the parking brake valve, it’s as if air gets hung up in the valve.  I used some model airplane fuel rubber hose to route the 5606 to a overflow jug.  
 

I was fortunate to get 5 gallons of “used” 5606 hyd fluid from leftovers on the military aircraft I work on…. The “old” fluid is pretty pristine in that it is pumped through some great filters when it is recirculated in the hyd “mule”, perfectly fine for a Mooney.  The military gets the stuff in 55 gallon drums….