So close - bleeding brakes

I was hoping to have already done my first flight but I can't seem to get over the hurdle. My last issue seems to be air in the lines of my brakes. I have tried various methods to try to push fluid in to the reservoir from the calipers and have had some success. What I am seeing now is air between the lines running from the pilot master cylinders to the passenger side(the high point in the loop of the lines). I have searched the forums for some advice but getting a mixed opinion if this is really an issue or not. I put an overflow can from the reservoir for the fluid to go in and I get fluid there but still haven't been able to get the air out between the master cylinders. My brakes feel solid but I want the air out to feel total confidence in them. Before I purchase another bleeder method just looking for some current feedback.

Have you tried to gravity bleed?

I also have a pressure bleeder your welcome to use also, we would have to come up with a fitting for reservoir but won't be an issue.

Worst thing with brakes is to frantically cycle them while bleeding, slow and steady. If you need a 2nd hand sometime Mike don't hesitate to ask.

If you can flex the line down below the reservoir then you can flick the tube with your finger to work the bubble up and out. If not, the option two is to remove one end and pressure bleed it out.
It is not likely to get into the pressure side of the system from there. I would not let it stop me from a first flight.

I wound up with a very small bubble there. I could not get the last bubble out the co-pilot master cylinder and it migrates there. The line between the co-pilot and pilot is only a supply line for the pilot brakes. Bubbles here will have no impact on braking action from the pilot master cylinders, assuming the closest bubble is at least a couple of inches from the pilot master cylinder.

For co-pilot side, the bubbles are on the pressure side and will compress to almost nothing (brake fluid doesn't compress) when co-pilot brakes are applied. If the total amount bubbles are small in volume, it will only result in a spongy feel and longer travel of the pedal to activate the brakes. If the bubble volume is large enough, you will run out of master cylinder travel before full pressure is achieved. If you can lock up the tires while moving, the bubbles are not creating a safety issue. Best to test when someone can activate the pilot brakes in case they are inadequate.

Larry

WE worked awhile on Raymo's 7A to get all the air out. Not only gravity, but bleeding form the bottom up. Then using the masters to pressurize the entire system. Great brakes.

Mike --it might take some patience to get them right, but take your time.

Tom

I had the exact same thing and I just took care of it yesterday. This part sucks, but I got under the dash on my stomach and cracked the line from the passenger side to the pilot side. I bled the lines going over to the pilot side by putting my finger on the end of the hose, push the pedal and let the fluid into a jar, then cap the line with my finger so it sucks fluid out of the reservoir again. Did this about 3 times until the lines were full then screwed the lines back down. As you are screwing the lines back into the top of the pilot cylinders it helps to put a slight slow pressure on the co pedals to keep forcing fluid through and keep there air out. No air and solid brakes on both sides. The worst part about it all is how cramped it is under there working. Took about 15 min and most of that was pulling the passenger seat out so I could lay in there comfortably.

This, from Harbor Freight, has performed wonders on difficult-to-bleed motorcycle brakes:

http://t.harborfreight.com/brake-fluid-bleeder-92924.html

Might be worth a try.

I'm going to give this a try when i bleed my brakes next time.

https://www.youtube.com/watch?v=zlnEVmSA_2c

I have bleed a lot of brakes on airplanes, motorhomes, trucks, cars, bikes, etc. Myself and every mechanic I know confirms completion by feel (when the brake pedal(s)/lever(s) are hard- you are done). The RV9a I built was the first vehicle that had opaqe plasic brake lines. I too ended up with an air bubble but brake pedals felt great. After a failed atempt to make the visual bubble disapear, I finally let it go. Airplane is flying, brakes work great from both sides, peddals are firm, and bubble still there. I wonder how many bubbles were present in all those vehicles I worked on over the years, they to worked great when I was done!

I bought a system from Avery Tools years ago. It Is a modified deck sprayer, and hooks into the bleed valve down by the caliper. It feeds the oil from the bottom up, quick and easy, no bubbles.

I have not seen the shop vac thing before. I have not bled the brakes on my -7 yet. The hardest brakes that I have ever had to deal with were on an equipment trailer with a surge hitch master cylinder and all the brake lines horizontal. The thing that worked for me was a HVAC vacuum pump. This can put a lot of pull on the system and it is a last resort for me. I like to pressure bleed from the reservoir if I can. You can put a little grease on the bleeder valve threads to reduce the air leakage when vacuum bleeding. This is not an issue when pressure bleeding.

I tried everything to get rid of some bubbles, while bleeding from the wheel cyl. Finally what worked for me was to crack the closest fitting and the air would head for that area and disappear..

Tapping on master cylinder

What everyone else said about putting fluid in from the bottom up AND
Tap lightly on the master cylinder with something like a 1/2" wrench.
The slight shock from the tapping makes the bubbles head uphill to the reservoir.
I have seen them go up a plastic line like magic.

post-mortem

Taking advice from others, Jeff (another 9A builder) and I went to the airport and pressure bleed the lines. I did have to break the lines loose at the master cylinders where they cross over to get those lines bleed as well. It looks like I still have a little air in the right side but for the most part the brakes are in much better shape. Will work some more on the right side to try to get the remaining air out. Thanks for all the help.

I just finished successfully bleeding my difficult brakes. I had sucess using a $9 home depot sprayer pressure filling the system. This alone left soft pedals so I followed it up with the harbor freight vacuum system. Sucking fluid the other way seemed to do the trick of dislodging the stubborn air. So a combination technique worked for me. Having ss brake lines and not being able to see the bubbles made it a little trickier.