VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Model Specific > RV-6/6A
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 08-14-2018, 11:14 PM
petehowell's Avatar
petehowell petehowell is offline
 
Join Date: Jan 2005
Location: MN
Posts: 2,168
Default Right Brake Won't Bleed, RV-6A

Here's the situation. Buddy has an RV-6A. We found a leaking, cracked flare at the right caliper and fixed it. Having a whale of time getting the air out of the right side brake system when we bleed. Pilot side brakes only. Has a soft pedal that can be pumped up to solid, then goes soft in a short amount of time. Left side has solid pedal, no problems.

Here's what we have done. Garden sprayer pressure bleeder from the bottom up. We've run several qts thru the system and out thru the reservoir. No bubbles coming out at the reservoir. Still a soft pedal.

We took the pressure side line off the master that goes over the top of the pedals and tried to get any air out of that - then rebled from the bottom up - soft pedal.

Replace master cylinder on the right side, re-bled, still soft pedal.

There is section of pressure side line that goes from the flex hose to to solid tube then up and over where the battery box used to be then on to the gear leg bulkhead fitting. That area looks ripe to store a bubble, any ideas how to flush it out better?

There are no fluid leaks we can see anywhere. Any tricks we are missing or areas to inspect further?

Thanks for any Ideas.......
__________________
Cheers,
Pete

Amateur Plane - RV-9A N789PH - 2050+ Hrs
Amateur Radio - KD0CVN
Doggies Delivered - 25+
St. Paul, MN

Last edited by petehowell : 08-15-2018 at 06:52 AM.
Reply With Quote
  #2  
Old 08-15-2018, 06:43 AM
9GT's Avatar
9GT 9GT is offline
 
Join Date: Jan 2010
Location: Southern Michigan
Posts: 1,494
Default

My building buddy has a Cozy MKIV that has a parking brake valve. Any time we do brake work on it where the system is opened, the parking brake valve will trap and hold some air when we bleed the brakes, even using the pressure pot method from the bleeder valve, he would always have a soft pedal. Took forever to trouble shoot but he has clear flex lines and we finally removed the valve from the mounting bracket and manipulated it around as the lines were being bled and out popped several air bubbles. Their may be a spot somewhere in your friends brake system holding air that get trapped and the pressure pot bleeding just can't push it out.
__________________
David C.
Howell, MI

RV-9A: Under Construction. N161RV (Reserved)
RV-10: N959RV Completed 12/29/2013 SOLD 08/23/2016

"Donor Exempt" but donated through Dec. 2018
Reply With Quote
  #3  
Old 08-15-2018, 07:19 AM
petehowell's Avatar
petehowell petehowell is offline
 
Join Date: Jan 2005
Location: MN
Posts: 2,168
Default no parking brake

Hi David,

No parking brake, but the line hoop over the battery box seems suspect to us. The line has bee successfully bled previously......
__________________
Cheers,
Pete

Amateur Plane - RV-9A N789PH - 2050+ Hrs
Amateur Radio - KD0CVN
Doggies Delivered - 25+
St. Paul, MN
Reply With Quote
  #4  
Old 08-15-2018, 08:20 AM
cajunwings cajunwings is offline
 
Join Date: Jun 2007
Location: new iberia la
Posts: 578
Default Bleeding Brakes

Some planes are notorious for being hard to bleed. For difficult cases I like a pressure pot from the bottom up with the highest flow the system will allow, then while flowing tap on the sides of the brake cylinders with something solid or rapidly pulse the brake pedal a small amount. Sometimes this will dislodge the air bubble from itís hiding place. To keep the mess to a minimum I have a fitting with a hose on it that replaces the reservoir fill plug during bleeding. Good luck.

Don Broussard
RV9 Rebuild in Progress
57 Pacer
Reply With Quote
  #5  
Old 08-15-2018, 08:28 AM
pa38112 pa38112 is offline
 
Join Date: Mar 2008
Location: Clarksboro, NJ
Posts: 597
Default

What size is the line the runs up to the battery box? Larger lines can be very difficult to purge, but since you said it has been done successfully before...
The higher the velocity the better. Instead of using a bleeder valve I would break the line at the closest fitting and pressure bleed it. Keep the pressure up high (10-15psi) the whole time.
Another, more difficult, trick is to insert a very small diameter line (miniature EVA tubing) into the brake line - measure the length so that it reaches just to the peak of the loop. You can then use a vacuum pump or suck on the line to remove air. you put the open port where you are inserting the tube in a cup of fluid so you do not introduce more air.
__________________
http://aprs.fi/N153MC
2004 RV6A Flying
Reply With Quote
  #6  
Old 08-15-2018, 02:45 PM
petehowell's Avatar
petehowell petehowell is offline
 
Join Date: Jan 2005
Location: MN
Posts: 2,168
Default 1/4 in tubing

The tube is the Van's plans std small 1/4", same that goes down the gear leg.


Quote:
Originally Posted by pa38112 View Post
What size is the line the runs up to the battery box? Larger lines can be very difficult to purge, but since you said it has been done successfully before...
The higher the velocity the better. Instead of using a bleeder valve I would break the line at the closest fitting and pressure bleed it. Keep the pressure up high (10-15psi) the whole time.
Another, more difficult, trick is to insert a very small diameter line (miniature EVA tubing) into the brake line - measure the length so that it reaches just to the peak of the loop. You can then use a vacuum pump or suck on the line to remove air. you put the open port where you are inserting the tube in a cup of fluid so you do not introduce more air.
__________________
Cheers,
Pete

Amateur Plane - RV-9A N789PH - 2050+ Hrs
Amateur Radio - KD0CVN
Doggies Delivered - 25+
St. Paul, MN
Reply With Quote
  #7  
Old 08-15-2018, 04:29 PM
azrv6's Avatar
azrv6 azrv6 is offline
 
Join Date: Mar 2006
Posts: 127
Default

I have one which is exhibiting similar behavior, have flowed quarts of brake fluid, bottom up under pressure, with no bubbles coming out the reservoir, and still a slightly soft pedal, but enough to hold at run up, but wish it was better.

I solved the other side by 1) bleeding bottom up, 2) bleeding top down, 3) bleeding bottom up. And it finally resulted in a rock solid pedal. Tried this same sequence on the trouble side to no avail.

Had to disconnect the master cylinder from the rudder pedal to allow me to shake the cylinder and adjacent lines while bleeding under pressure. Gave me just enough movement in the lines to shake a bubble free.

Makes sure the garden sprayer bleeder isn't introducing air into the stream of fluid. I ended up not using the pump handle to pressurize the sprayer. Instead I installed a fitting into the top of the sprayer tank and pressurized the headspace above the brake fluid in the tank using my air compressor and a quality regulator. Ended up using about 15 psi.

Put a little dab of grease on the tubing where you connect the fluid feed to the bleeder valve to keep air from being introduced there.

Once you get this solved, please post what you think did the trick.
__________________
Dave Binkley
RV-6, O-360-A1A, C/S
1932 Monocoupe 110, Warner 145 (http://gobinkley.com)
Sedona, AZ
Reply With Quote
  #8  
Old 08-15-2018, 06:14 PM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 4,511
Default

Get it yet Pete? How much pressure on that sprayer? I tested mine with a gage to count x number of pumps to 30 psi. Then you might have to crack the fitting loose at one of the master to get the flow higher until that bubble comes through.

Hope you got it already, though.

Great to see you at OSH and meet Andi.
__________________
Bill

RV-7
1st Flight 1-27-18
Phase II 8-3-18
Reply With Quote
  #9  
Old 08-16-2018, 05:55 AM
FredMagare FredMagare is offline
 
Join Date: Mar 2006
Location: Kyle, TX
Posts: 534
Default

Impossible to say for certain but perhaps your master cylinder is leaking internally? Do you have firm peddle pressure and brake application but the peddle creeps while holding brakes? If so, replace the master cylinder.

I hope this helps.
__________________
Fred Magare
GySgt, USMC (Ret.)
Frederic.magare "at" gmail.com
RV-9A SB Fuselage / Finish Kit on-hand
[Engine and CS Prop still to acquire]
Reply With Quote
  #10  
Old 08-16-2018, 06:59 AM
petehowell's Avatar
petehowell petehowell is offline
 
Join Date: Jan 2005
Location: MN
Posts: 2,168
Default Thanks Guys

The owner's dad had a med procedure so we are taking a few days off. Some responses below.

Fred - Master cylinder is has been replaced, so unless old and new had same defect, I think we can rule that out.

Bill - I dont know the pressure, but I have a way to measure and will check it. We the hose off at the master and bled there, but did not try just cracking 0 maybe we let some air back in - good idea. (Andi loved meeting you, too!)

Dave - Shaking the master, and dab of grease on the nipple - we will try, Top down bleed - will try this, too. Several other systems bled easily (RV7/9) with this system have been easy and solid pedal, and clear line shows no bubble out of the sprayer, but we will try an RC fuel pump next to see if that could be it.

Thanks guys! will report back!
__________________
Cheers,
Pete

Amateur Plane - RV-9A N789PH - 2050+ Hrs
Amateur Radio - KD0CVN
Doggies Delivered - 25+
St. Paul, MN

Last edited by petehowell : 08-16-2018 at 07:04 AM.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 01:00 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.