Brakes wont hold pressure - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Suspension - Brakes - Steering
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 10-04-2013, 03:16 PM
Newbie37's Avatar
Newbie 37
 

Last journal entry: Three months since started
Last photo:
Join Date: Jul 2013
Location: Oakdale, ca
Age: 56
Posts: 164
Wiki Edits: 0

Thanks: 153
Thanked 13 Times in 12 Posts
Brakes wont hold pressure

On my 37 chev i put four wheel disc brakes, all new lines with 2 psi pressure valves, new master cylinder and proportioning valve from speedway specifically for 4 wheel manual disc brakes. Bled the system several times both manually and with pressure bleeder and i can pump up the brakes and they hold but as soon as i release them it goes to the floor on next attempt to put brakes on, any help would be appreciated.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 10-05-2013, 09:06 AM
S10xGN's Avatar
Gotta love a turbo!
 

Last journal entry: Body on Frame today.
Last photo:
Join Date: Aug 2004
Location: Port Neches, TX
Age: 61
Posts: 1,662
Wiki Edits: 0

Thanks: 0
Thanked 62 Times in 58 Posts
That's a symptom of the master cylinder's volume being inadequate for the wheel cylinders. Have you looked at the technical info on Wilwood's site? I believe they show how to calculate the necessary m/c bore so it has enough fluid to actuate the calipers on one stroke. It could be other things... Have you mounted the calipers with the bleeder screws at the top? If they're even off a little, air cannot be fully purged (I know this from experience).

Russ
Reply With Quote Quick reply to this message
The Following User Says Thank You to S10xGN For This Useful Post:
Newbie37 (10-18-2013)
  #3 (permalink)  
Old 10-18-2013, 10:47 AM
34 chevy truck 410 merc power
 
Last photo:
Join Date: Sep 2005
Posts: 861
Wiki Edits: 0

Thanks: 107
Thanked 134 Times in 129 Posts
Another way to check this is...if you can pump the brakes up ? If you hold the pedal, does it creep down, or pedal start going to the floor slowly. You have to hold and wait for a bit to see if this happens. If so, bad master cylinder, new or not. With disc brakes, once you have moved the disc pads close to the rotors, they pretty much stay adjusted. If all this checks, and the calipers are not binding the pads, and they are close to the disc, then most likely, the master is bad. Especially if you bought this as a set.
Reply With Quote Quick reply to this message
The Following User Says Thank You to Denny For This Useful Post:
Newbie37 (10-18-2013)
  #4 (permalink)  
Old 10-20-2013, 08:35 AM
Newbie37's Avatar
Newbie 37
 

Last journal entry: Three months since started
Last photo:
Join Date: Jul 2013
Location: Oakdale, ca
Age: 56
Posts: 164
Wiki Edits: 0

Thanks: 153
Thanked 13 Times in 12 Posts
Ok , so i changed my setup, went to power four wheel disc , new master cylinder and booster on firewall. After many attempts to bleed system and no success i decided to plug off rear brake line trying to figure out where my problem is and i have good pressure and brake on the front but when i connect the rear line it goes to the floor instantly. I looked for leaks in the rear lines but dont have any. Tried pressure bleeding and manually bleeding the rears again but no different. What am i missing? Is the combo valve bad? Is the master bad? Do i have a kinked hardline. Please help. Im very frustrated
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 10-20-2013, 09:26 AM
34 chevy truck 410 merc power
 
Last photo:
Join Date: Sep 2005
Posts: 861
Wiki Edits: 0

Thanks: 107
Thanked 134 Times in 129 Posts
Which 4 wheel disc kit did you get ? A part number would help. Without knowing just what kit, it's a little hard to help on the problem.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 10-20-2013, 09:50 AM
Newbie37's Avatar
Newbie 37
 

Last journal entry: Three months since started
Last photo:
Join Date: Jul 2013
Location: Oakdale, ca
Age: 56
Posts: 164
Wiki Edits: 0

Thanks: 153
Thanked 13 Times in 12 Posts
The front disc brakes are a mustang II , rear kit is from speedway for ford nine inch rear end. I tried bypassing the rear line straight to the master cylinder and still np pressure to rear brakes. Disconnect rear and plug master and fronts are good. Rear caliper part numbers are. 91031046L. 91031046 R. Master cylinder and booster i bought from rodparts as a combo unit. And yes the calipers bleeders are on top. Lol. I am using a combination valve. Should i be using just a distribution block?

Last edited by Newbie37; 10-20-2013 at 09:58 AM.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 10-20-2013, 10:01 AM
34 chevy truck 410 merc power
 
Last photo:
Join Date: Sep 2005
Posts: 861
Wiki Edits: 0

Thanks: 107
Thanked 134 Times in 129 Posts
Ok. Did you have a helper pump the brakes when you had the line connected to the rear ? And once pumped up, crack the bleeder ? Did any fluid come out ? If so, any air ? If...you got all fluid out on both rears, And still the pedal goes to the floor. It kind of points to that section of the master cylinder not working correctly. A side note, does the master cylinder have some play before it engages ? The small rod in between the master and booster. There must be some play there, or the cups inside the master will not clear the holes to allow fluid to inter the bore.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 10-20-2013, 10:21 AM
Newbie37's Avatar
Newbie 37
 

Last journal entry: Three months since started
Last photo:
Join Date: Jul 2013
Location: Oakdale, ca
Age: 56
Posts: 164
Wiki Edits: 0

Thanks: 153
Thanked 13 Times in 12 Posts
I vacuum bled and manually also. Checked for play on the rod and i have maybe 1/8 play. I also removed the cap on the master and pump the brake and it shoot up from both sides of the master so its definitaly opening both sides for flow.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 10-20-2013, 10:27 AM
34 chevy truck 410 merc power
 
Last photo:
Join Date: Sep 2005
Posts: 861
Wiki Edits: 0

Thanks: 107
Thanked 134 Times in 129 Posts
Ok, that sounds good. So did you get any fluid out of the wheel cylinder when you pumped the brakes up, and someone else cracked the bleeder open ? Be careful though. I once had the wife help me, and she was pumping the clutch pedal...
You mentioned a combo valve. Is this a proportioning valve ? If so, it could be shifted to close one side. Make sure it is centered for fluid to flow to all wheels.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 10-20-2013, 10:44 AM
Newbie37's Avatar
Newbie 37
 

Last journal entry: Three months since started
Last photo:
Join Date: Jul 2013
Location: Oakdale, ca
Age: 56
Posts: 164
Wiki Edits: 0

Thanks: 153
Thanked 13 Times in 12 Posts
Got fluid out of rear calipers, combination valve is the proportion valve, block all in one, and i dont have a clutch lol
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 10-20-2013, 10:49 AM
S10xGN's Avatar
Gotta love a turbo!
 

Last journal entry: Body on Frame today.
Last photo:
Join Date: Aug 2004
Location: Port Neches, TX
Age: 61
Posts: 1,662
Wiki Edits: 0

Thanks: 0
Thanked 62 Times in 58 Posts
With a problem like this, I'd recommend starting over. Bench-bleed the master first, you can do this on the car the "old way" with loopback lines or the new way by using plugs in the outlet ports. I've used both methods and prefer the loopback lines. Those plastic plugs seem like they'd blow out under pressure but seem to work OK. Any air will come from the lines, the inner ports, or both. Once you see no more air bubbles, connect the lines and let them gravity fill by cracking open the bleeders while NOT letting the master run empty. Once you get fluid at each bleeder, close that one until all are closed. Now try bleeding the system. Are you getting good fluid flow at each bleeder? Are the bleeders at the highest point (top) of the caliper? If they are off even a little, trapped air will not be purged correctly. You can also help moving the bubbles by rapping the calipers with a deadblow hammer...




HTH,

Russ
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 10-20-2013, 11:08 AM
Newbie37's Avatar
Newbie 37
 

Last journal entry: Three months since started
Last photo:
Join Date: Jul 2013
Location: Oakdale, ca
Age: 56
Posts: 164
Wiki Edits: 0

Thanks: 153
Thanked 13 Times in 12 Posts
Ok guys thx for the input, enough for today, football games going to start lol. Tommorrow i will start over from the beginning.
Reply With Quote Quick reply to this message

Recent Suspension - Brakes - Steering posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

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

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Front BRAKES Won't hold stinkin linkin Suspension - Brakes - Steering 6 04-14-2013 11:36 AM
BRAKES WON"T HOLD Ossie Suspension - Brakes - Steering 3 06-02-2012 10:09 AM
1988 Chevy, 700r4 Wont hold in first gear. jjack010 Transmission - Rearend 10 02-23-2012 07:18 PM
Help! Brakes wont build pressure... they did before I replaced the lines? honster919 Suspension - Brakes - Steering 6 06-06-2011 08:23 AM
How long does your pump hold pressure? 001mustang Engine 9 12-30-2009 11:32 PM


All times are GMT -6. The time now is 06:51 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.