VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.






VAF on Twitter:
@VansAirForceNet

  #1  
Old 09-08-2022, 04:34 PM
phapp phapp is offline
 
Join Date: Mar 2008
Location: Walpole, NH
Posts: 75
Default Break Bleed Questions

Hi,
-8, Matco masters and Cleveland calipers. I know about the check-valve. Same both sides.

At home before moving my RV-8 to the airport, I had the brakes bled and a firm pedal (pumped fluid up from the calipers). At the airport a year later I cannot get pressure build up at all even though I can see no air bubbles in the clear reservoir lines. I do have the tail up on a stand and the fuse level.

Is it possible to have an air leak without any fluid leaks? Could stuck caliper pistons be the issue (really, both?) ? Should I be tail down? Might I need to pull and rebuild the masters if they can leak air and not fluid?

Looking for the Occam's razor solution here even if it's the most labor intensive.

I was hoping to upgrade the insurance to "in motion" and do the first start and fuel flow test (and taxi) before snow flies. But not without brakes.

Thanks for any advice.
__________________
2021 - 2022 Dues Paid
N423PH Schweizer 1-23 (Sold)
N83881 Champ 7AC
N446PH RV8 (reserved)
PA-25 Pawnee Glider Tow Pilot (volunteer)
CallAir A-9 Glider Tow Pilot (volunteer)
Reply With Quote
  #2  
Old 09-08-2022, 05:25 PM
D-Dubya D-Dubya is offline
 
Join Date: May 2009
Location: Beaumont, Texas
Posts: 237
Default Need Some Clarification

When you say you can't get any pressure build up, what is your actual indication of that? Is the pedal spongy? Do the brakes not hold when you push it around the taxiway?

To address some of your questions, I would think if you had an air leak, you would see fluid. And it shouldn't matter if the tail is up or down. Unless you have the spinner in the dirt. You have much bigger problems if that's the case.

I believe I have the original Cleveland master cylinders that came with the kit, and their operation is a little different than the Matco cylinders. So I may not be too much help here. But surely the group can figure out something for you to start looking at.
__________________
David Welsh
Beaumont, TX
RV-7 N413WD
Reply With Quote
  #3  
Old 09-08-2022, 07:48 PM
gasman gasman is offline
 
Join Date: Mar 2007
Location: Sonoma County
Posts: 4,760
Default

The only time you will get air in the system after the initial bleed, is to wear out both pads and have a fluid leak at a fitting. Air can't leak in, only fluid can leak out. If you don't have a fluid puddle.... you don't have a leak.

There is no check valve in the brake system.... so I don't understand that statement.
__________________
VAF #897 Warren Moretti
2022 =VAF= Dues PAID
Reply With Quote
  #4  
Old 09-08-2022, 08:31 PM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 5,141
Default

I had an extremely frustrating time bleeding the brakes on my -10. I was using a pump up sprayer to force fluid in from the bottom up. I kept getting bubbles in the lines.

Turned out that the way my pump-up sprayer worked, when you pumped it, it created air bubbles in the fluid in the tank. The more you pumped up the tank, the smaller the bubbles were (the old PV=NRT thing). When you pumped the fluid into the lines, the bubbles expanded and made things a nightmare.

Going forward I'll use a syringe or pump oiler to bleed brakes.
__________________
Kyle Boatright
Marietta, GA
2001 RV-6 N46KB
2019? (actually 2022) RV-10 N46BX
Reply With Quote
  #5  
Old 09-08-2022, 09:30 PM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 3,278
Default Mity vac

I used a mighty vac attached to the reservoir. Put a jar of fluid at the bleed screw, open the screw and the fluid moves from the caliper to the reservoir with zero bubbles. Easy peasy.
__________________
Bob
EAA Tech Counselor
Aerospace Engineer '88

RV-10-ER
N464RL
In Paint at Evoke!
Garmin G3X-T, Barrett EFII S32, CAI, MTV-9B

Dues+ Paid 2022,...Thanks DR+
Reply With Quote
  #6  
Old 09-09-2022, 08:23 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 8,032
Default

Air can get introduced in different ways or it may not be air at all. A defect or failed seal in the master cylinder can also prevent the brake system from building pressure, without fluid leaking out of the system. Not sure there is a magic bullet answer for you here. You are going to need to dig in and figure out the issue. If it were me, I would repeat the bleeding process and see what results. While you can see the upstream side of the system, everything downstream from the MC is not visible so you have no idea what is in there.

Larry
__________________
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019

Last edited by lr172 : 09-09-2022 at 08:26 AM.
Reply With Quote
  #7  
Old 09-09-2022, 12:06 PM
bjdecker's Avatar
bjdecker bjdecker is offline
 
Join Date: Jun 2005
Location: Georgetown, TX
Posts: 1,415
Default Sealant

Check all those NPT (or ANPT) fittings for the correct sealant.

Do not use EZ TURN - FUEL LUBE on NPT fittings (kicking myself repeatedly). It is an anti-seize/lubricant compound and will NOT seal NPT threads.

Only use Permetex #2, Locktite 5xx series (565 is what Van's recommends, but 567 and 592 are ok as well)
Attached Thumbnails
Click image for larger version

Name:	Screen Shot 2022-09-09 at 12.05.01 PM.png
Views:	67
Size:	883.0 KB
ID:	30744  
__________________
Brian Decker
RV-7 (Flying)
Reply With Quote
  #8  
Old 09-09-2022, 12:26 PM
Taltruda Taltruda is offline
 
Join Date: Oct 2017
Location: Las Vegas, NV
Posts: 1,445
Default

Quote:
Originally Posted by bjdecker View Post
Check all those NPT (or ANPT) fittings for the correct sealant.

Do not use EZ TURN - FUEL LUBE on NPT fittings (kicking myself repeatedly). It is an anti-seize/lubricant compound and will NOT seal NPT threads.

Only use Permetex #2, Locktite 5xx series (565 is what Van's recommends, but 567 and 592 are ok as well)
I love Locktite 567.. itís the high temp version of 565. I use it in all tapered pipe threads. Itís amazing how many people still use fuel lube and think they are using the correct thing.. eventually the fuel lube WILL leak. Like you said, itís a lube, not a sealant!
__________________
Tom
Las Vegas
RV-4 flyingÖ
RV-8 empenage finished 10-2020

Wings Started.. 11-2020
Reply With Quote
  #9  
Old 09-09-2022, 01:18 PM
LouFly's Avatar
LouFly LouFly is offline
 
Join Date: Sep 2016
Location: St. Louis MO
Posts: 114
Default

Quote:
Originally Posted by Taltruda View Post
I love Locktite 567.. itís the high temp version of 565. I use it in all tapered pipe threads.
I have been using 567 and wondering if there was a downside to that in lieu of 565.
__________________
Bob Miller
RV-6A bought flying, GN-1 resurrected & flying
2022 -=VAF=- Contributor
Reply With Quote
  #10  
Old 09-09-2022, 04:55 PM
rockwoodrv9 rockwoodrv9 is offline
 
Join Date: Dec 2011
Location: Meridian ID, Aspen CO, Okemos MI
Posts: 3,262
Default

Bleeding the breaks is one of the things I really hate. I have not had much luck and it has taken me days to get them correct. Having the clear tubes may help or not. Iím not sure. Maybe the braided lines hide some of the bubbles that probably donít matter!

I had best luck with drip from the top and vacuum pressure from the bottom.
Good luck
__________________
rockwoodrv9a
Williamston MI
O-320 D2A
Flying N376E
2023
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 04:51 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.