No power brakes
#1
Hi everyone. 
I need some major help.  Huh Huh
I can not seem to get the power brake to work. I might as well cut a hole in floor pan and use the Fred Flintstone method of stopping. Lol
I’ve disconnected the manifold vacuum and installed a external vacuum pump feeding directly to the new master cylinder and new brake booster to no avail.  Lines have all been bled extensively. 

I can put my full weight on the brake peddle and it will barely but slowly stop the car. It feels like the brakes are trying to engage, but just don’t have the pressure to do the job. 
 Is it possible that it’s a problem in the drumbs or disk brakes. 

Would appreciate any advice you can give.
Reply
#2
What are you working on, 1969, 1970, etc. and is it a factory power brake car or did you or a previous owner convert it to power brakes?

My initial guess is your new booster is bad.  It's always best to have your old OEM booster rebuilt or buy a rebuilt OEM booster from places like West Coast Classic Cougars.  Parts store boosters are often garbage.  And that repro booster that Scott Drake offers is merely a cheap China universal import with a mounting plate attached to it.
Reply
#3
(06-12-2019, 09:23 AM)1969_Mach1 Wrote: What are you working on, 1969, 1970, etc. and is it a factory power brake car or did you or a previous owner convert it to power brakes?

My initial guess is your new booster is bad.  It's always best to have your old OEM booster rebuilt or buy a rebuilt OEM booster from places like West Coast Classic Cougars.  Parts store boosters are often garbage.  And that repro booster that Scott Drake offers is merely a cheap China universal import with a mounting plate attached to it.

71 Mach1  Came with factory power booster front disc rear drum. So far even my mechanic can’t figure it out. That’s why I’m asking.
Reply
#4
How strong is the vacuum signal to the booster, if it's less than about 14" the power assist starts to suffer.  12" of vacuum to the booster is really the minimum for any type of power assist.  If the vacuum signal is okay, I'd think you have a bad booster.  Where did your mechanic get the new booster?

Just to clarify, the brakes will work, just the pedal force needs to be extremely high?  Asking, because if the won't work at all regardless of how much you push on the pedal, there is a chance something hydraulic is plugged somewhere.  But, if something is plugged, you should still feel some power assist.

One test I have heard of is with the engine off press the pedal several times to eliminate any residual vacuum inside the booster.  Then, while very lightly touching the brake pedal start the engine.  If the booster is working you should feel the brake pedal pull down a little bit.
Reply
#5
(06-13-2019, 02:41 AM)1969_Mach1 Wrote: How strong is the vacuum signal to the booster, if it's less than about 14" the power assist starts to suffer.  12" of vacuum to the booster is really the minimum for any type of power assist.  If the vacuum signal is okay, I'd think you have a bad booster.  Where did your mechanic get the new booster?

Just to clarify, the brakes will work, just the pedal force needs to be extremely high?  Asking, because if the won't work at all regardless of how much you push on the pedal, there is a chance something hydraulic is plugged somewhere.  But, if something is plugged, you should still feel some power assist.

One test I have heard of is with the engine off press the pedal several times to eliminate any residual vacuum inside the booster.  Then, while very lightly touching the brake pedal start the engine.  If the booster is working you should feel the brake pedal pull down a little bit.

Thanks. I will double check the vacuum pressure but I think it’s going. I’ll also try that test. As far as the brakes working! They barely do. Put my full weight on the peddle as far as it goes down. I can feel the brake making contact with pads but it like there not applying any pressure to the pads. Feels like they are just touching or rubbing against them.  Does this do much good.
Reply
#6
(06-13-2019, 01:09 PM)Dave Allred Wrote:
(06-13-2019, 02:41 AM)1969_Mach1 Wrote: How strong is the vacuum signal to the booster, if it's less than about 14" the power assist starts to suffer.  12" of vacuum to the booster is really the minimum for any type of power assist.  If the vacuum signal is okay, I'd think you have a bad booster.  Where did your mechanic get the new booster?

Just to clarify, the brakes will work, just the pedal force needs to be extremely high?  Asking, because if the won't work at all regardless of how much you push on the pedal, there is a chance something hydraulic is plugged somewhere.  But, if something is plugged, you should still feel some power assist.

One test I have heard of is with the engine off press the pedal several times to eliminate any residual vacuum inside the booster.  Then, while very lightly touching the brake pedal start the engine.  If the booster is working you should feel the brake pedal pull down a little bit.

Thanks. I will double check the vacuum pressure but I think it’s going. I’ll also try that test. As far as the brakes working! They barely do. Put my full weight on the peddle as far as it goes down. I can feel the brake making contact with pads but it like there not applying any pressure to the pads. Feels like they are just touching or rubbing against them.  Does this do much good.

With the car on jackstands have you tried having one person manually rotate a tire and another apply the brakes?  Just trying to determine if something is plugged, but, since you mentioned in your first post they were bled extensively it's starting to look there is no power assist.


Is the pedal going nearly to the floor?  First, if there is no air in the system and the master cylinder is leaking internally the pedal with go nearly to the floor and the brakes will not work.  Second, rear brakes far out of adjustment will cause the pedal to travel too far and the brakes will work but not as well as they should.
Reply


Possibly Related Threads...
Thread Author Replies Views Last Post
  1969 mach1 brakes to right side rindel 5 5,477 11-23-2015, 02:48 AM
Last Post: JTS71 Mach1
  Cause these are the brakes! DNA 6 6,445 09-01-2015, 03:06 AM
Last Post: Mach1FatherFigure
  69 Mach I Brakes - Hard pedal Must69ang 4 7,724 04-15-2015, 08:31 AM
Last Post: Must69ang
  Brakes not holding pressure?!?! armyfox 6 6,981 06-09-2013, 10:46 AM
Last Post: 68machowner
  Power Steering Pump Aftermarket Rocketman 2 5,316 07-06-2012, 10:04 AM
Last Post: JTS71 Mach1
  Electrical power rack (steering) chutsonjr@yahoo.com 3 6,069 03-28-2011, 02:01 PM
Last Post: chutsonjr@yahoo.com
  power stearing sportroof 0 2,905 01-02-2011, 05:31 AM
Last Post: sportroof
  power windows go bears 5 6,694 03-14-2010, 08:09 AM
Last Post: go bears

Forum Jump:


Users browsing this thread: 1 Guest(s)
[-]
Latest Threads
72 351C starts to overheat at idle
Last Post: SteveO_71
Yesterday 12:18 AM
» Replies: 16
» Views: 2535
new autolite volt reg keeps alt light on
Last Post: 1969_Mach1
07-20-2019 01:41 PM
» Replies: 10
» Views: 450
Manual Trans Gear Oil
Last Post: martinbrown1276
07-19-2019 10:04 PM
» Replies: 13
» Views: 3412
New Member and 69 Mach 1 owner
Last Post: bob.harlan
07-19-2019 02:42 AM
» Replies: 2
» Views: 209
Stock Cam Specs - 69 351w 4v ?
Last Post: yashasvi07
07-18-2019 06:51 PM
» Replies: 71
» Views: 50206
Happy Birthday America!!!
Last Post: Mustangmike
07-05-2019 09:45 AM
» Replies: 2
» Views: 918
69 Mach 1 rear seat install
Last Post: rindel
06-29-2019 02:44 AM
» Replies: 8
» Views: 1897
1973 Mach 1 parts
Last Post: locknload
06-28-2019 12:14 PM
» Replies: 8
» Views: 3334
headers for 1969 mach 1
Last Post: rango-jr
06-23-2019 11:37 AM
» Replies: 11
» Views: 2670
Been Awhile... '71 Rustang
Last Post: Steven Harris
06-21-2019 01:52 PM
» Replies: 148
» Views: 129437
Bezel for power seat switch
Last Post: 1969_Mach1
06-21-2019 02:28 AM
» Replies: 2
» Views: 569
Happy Dad's Day!!!
Last Post: BLACK JADE 69
06-18-2019 12:31 AM
» Replies: 1
» Views: 537
No power brakes
Last Post: 1969_Mach1
06-14-2019 03:12 AM
» Replies: 5
» Views: 1065
69 Mach 1 Headlight switch reinstall iss...
Last Post: combat32
06-03-2019 11:58 PM
» Replies: 16
» Views: 3351
66 Fairlane Project
Last Post: Mustangmike
06-02-2019 11:20 AM
» Replies: 587
» Views: 233058
Is this noise normal?
Last Post: 1969_Mach1
05-31-2019 08:36 AM
» Replies: 15
» Views: 4909
What is this?
Last Post: Oztrailer
05-25-2019 07:23 PM
» Replies: 6
» Views: 1324
hdshadpar
Last Post: hdshadpar
05-24-2019 12:52 AM
» Replies: 5
» Views: 3054
Shaker Rebuild
Last Post: Bambus
05-17-2019 02:18 AM
» Replies: 12
» Views: 4363
Mustang GT Transmission Issue Overrated?
Last Post: Mustangmike
04-26-2019 07:40 PM
» Replies: 1
» Views: 2157

>