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Old 09-29-2010, 12:55 PM   #1
jam0o0
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brake pedal stays down

ok so looked through threads back to '05 and didn't find anything.

i just went to pull the bronco out of the garage after a few months of working on things. during this time i started it every few weeks but it never got moved.

i pressed the pedal to get the truck out of park. then let go of the brake to back out....truck doesn't move. give it gas...truck leans and doesn't move. 2 minutes of looking at stuff. i get in and pull up on the pedal and the truck rolls back like normal. every time i press the brakes now the pedal stays down untill i pull it up.

any ideas? i've changed a lot of stuff this summer. short list that might be related:
-redid all the vacume lines
-pulled the vacume res
-pulled the a.i.r. system (left the electric valves in and just didn't run vacume line to them)
-new headers (the brake lines run close to them but are wrapped in heat sleaves.
-pulled the cruse (left the brake sensor in place, just unplugged it.)

the entire system is 1.5 years old (reman parts mostly) with less than 3k miles on it. brake system:
'95 f350 master and booster
'89 f350 front calipers and rotors
'90's chevy 1/2 ton front calipers on rear
'96 e350 rear rotors
jegs prop valve on rear
ABS all gone.
ford drum residual pressure valve in rear circuit gutted.
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Old 09-29-2010, 01:10 PM   #2
Northernguy
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This is what I think but its just a guess.-"-pulled the cruse (left the brake sensor in place, just unplugged it.)"
Bleed the system.
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Old 09-29-2010, 01:29 PM   #3
jam0o0
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i unplugged the electrical connector from the electric harness. nothing with the hydraulics was changed.
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Old 09-29-2010, 01:33 PM   #4
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The exact same thing happened to me when I was gifted a 1994 F250. I flushed the heck out of the brake hydraulic system with my Motive Power Bleeder to get out the old heavily contaminated fluid and all is well!
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Old 09-29-2010, 01:43 PM   #5
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Go here: www.broncolinks.com ~ you may able to find some answers there, it's loaded with tech info and diagrams etc.

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Old 09-30-2010, 05:18 PM   #6
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so here's the short list for things to check today (reference for me for later)
1. grease all the caliper sliders
2. inspect petal assembly
3. separate master from booster
- test booster alone with engine off and engine running
- test master without booster
4. put vacuum res back on. -> test

the list of things that it could be spans every part of the system. booster, master, caliper, caliper seals, rust pad-rotor, old fluid, pedal, push-rod alignment.
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'93 F250 7.3 turbo, ZF5, 2wd, excab, long bed.
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Old 09-30-2010, 09:11 PM   #7
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Quote:
Originally Posted by jam0o0 View Post
so here's the short list for things to check today (reference for me for later)
1. grease all the caliper sliders
2. inspect petal assembly
3. separate master from booster
- test booster alone with engine off and engine running
- test master without booster
4. put vacuum res back on. -> test

the list of things that it could be spans every part of the system. booster, master, caliper, caliper seals, rust pad-rotor, old fluid, pedal, push-rod alignment.
Just start by flushing your hydraulic system. You should be doing that annually anyway... Look at your master cylinder and see if the brake fluid is dark or clear.
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Old 10-01-2010, 10:26 AM   #8
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update:

-brake fluid in the master is clearer than the bottle i on the shelf at napa. i'm not changing it. i'll deal with having to manually pull up on the pedal before i deal with bleeding the system again.
-i greased the sliders on the calipers and the pedal no longer stays down. but it is really slow coming back up.
-playing with the brakes with the engine off they feel normal.
-after playing with the brakes when i turned on the engine the pedal went down on it's own. then came back up slowly.
-there is no indication of problems with the vacuum system (a/c, vents, unstable idle)

i'm 90% sure it's the return spring in the master that is worn out. it was a cheep reman master. at this point it'll stay until it dies or the wheeling season is over. when it's time to change it i'll put the truck on my trailer. add the line locks, re-pumb the brake lines around the master cylinder and header. then drag it straight to a shop for them to mess with bleeding the brakes.

in case anyone wants to know why i'm against bleeding the brakes it's cause last time i spent a month (using up a lot of good will with my father and g/f who i had to conscript to help) messing with it trying to get all the air out of the system and get a good pedal. i ended up driving the truck to a shop with a lead car to make sure i didn't have to stop on the way cause it wouldn't stop. this was the 4th vehicle i've bled the brakes on and it's the first one i couldn't do.
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'93 F250 7.3 turbo, ZF5, 2wd, excab, long bed.
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Old 10-01-2010, 01:38 PM   #9
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yo
This is from the 1996 F-150, F-250, F-350, and Bronco Workshop Manual

Slow Brake Pedal Return
Excessive seal friction in power brake booster.
REPLACE power brake booster. REFER to Section 06-07A.

Flared reaction end.
REPLACE power brake booster.

Broken piston return spring.
REPLACE power brake booster.

Heavy brake pedal.
REPOSITION brake pedal or ADD retracting spring. REFER to Section 06-06.
GO to Pinpoint Test:

Pinpoint Test
L1 BRAKE PEDAL RETURN
Run engine at fast idle while making several brake applications.
Pull brake pedal rearward with approximately 44.5N (10 lbs.) force.
Release the brake pedal and measure the distance to the toe board.
Make a hard brake application.
Release the brake pedal and measure the brake pedal to toe board distance. The brake pedal should return to its original position.
Did brake pedal return to original position?
Yes
Vehicle OK.
No GO to L2.

L2 BRAKE PEDAL BINDING
Check brake pedal for sticking or binding.
Is the brake pedal operating freely?
Yes REPLACE power brake booster.
No CORRECT any sticking or binding. REPEAT L2.
=======
Brake Booster, Power
CAUTION: Make sure the power brake booster rubber reaction disc is properly installed as shown in the illustration. If the power brake booster-to-brake master cylinder push rod is removed or accidentally pulled out, it may dislodge the power brake booster rubber reaction disc from its seat in the power brake booster (2005). Symptoms of a dislodged power brake booster rubber reaction disc are excessive brake pedal travel and extreme power brake sensitivity. If the power brake booster-to-brake master cylinder push rod is removed, remove the power brake booster front seal and look into the power brake booster to where the power brake booster-to-brake master cylinder push rod seats. The power brake booster rubber reaction disc is black rubber. If the power brake booster rubber reaction disc is dislodged, a silver colored valve plunger will be exposed. If the power brake booster rubber reaction disc cannot be located, installed and aligned, then the power brake booster unit must be replaced.



Item Part Number Description
1 2005 Power Brake Booster
2 — Valve Plunger (Part of 2005)
3 — Brake Pedal-to-Power Brake Booster Push Rod
(Part of 2005)
4 — Power Brake Booster Rubber Reaction Disc (in Position) (Part of 2005)
5 — Power Brake Booster-to-
Brake Master Cylinder Push Rod (Part of 2005)
6 — Power Brake Booster Front Seal (Part of 2005)
--
Removal

NOTE: When the battery is disconnected and reconnected, some abnormal drive symptoms may occur while the powertrain control module (PCM) (12A650) relearns its adaptive strategy. The vehicle may need to be driven 16 km (10 miles) or more to relearn the strategy.



Disconnect the battery ground cable (14301).

Support the power brake booster from the underside with a prop.

Loosen the clamp that secures the vacuum booster hose to the power brake booster check valve, and remove the vacuum booster hose. Remove the power brake booster check valve.

Remove the wraparound clip (securing brake lines) from power brake booster inboard stud.

Remove the brake master cylinder-to-power brake booster retaining nuts.

Pull the brake master cylinder (2140) off the power brake booster and leave it supported by the prop, far enough away to allow removal of the power brake booster.

From inside the cab, remove the cotter pin and slide the stoplight switch (13480), brake master cylinder push rod spacers (2B129) and brake master cylinder push rod bushing (2474) off the brake pedal pin.

From inside the cab, remove the nuts retaining the power brake booster to the dash. Remove the power brake booster from the engine compartment.


Item Part Number Description
1 2005 Power Brake Booster
2 13480 Stoplight Switch
3 2140 Brake Master Cylinder
4 382802-S2 Nut
5 2474 Brake Master Cylinder Push Rod Bushing
6 2B129 Brake Master Cylinder Push Rod Spacer
7 2467 Brake Pedal Bracket
8 380699-S100 Self-Locking Pin
A — Tighten to 20-28 Nm
(15-21 Lb-Ft)
--
Installation

NOTE: Make sure the brake pedal-to-power brake booster push rod is positioned on the correct side of the brake pedal (2455) to install onto the brake pedal pin prior to tightening the power brake booster to the dash.



Mount the power brake booster on the engine side of the dash panel by sliding the brake pedal bracket mounting studs and brake pedal-to-power brake booster push rod in through the holes in the dash.

Install the brake pedal bracket-to-dash panel retaining nuts from inside the cab. Tighten nuts to 20-28 Nm (15-21 lb-ft).

Position the brake master cylinder on the power brake booster. Install the retaining nuts and remove the prop from underneath the brake master cylinder. Tighten nuts to 20-28 Nm (15-21 lb-ft).

Install the wraparound clip on the booster inboard stud.

Install the power brake booster check valve. Connect the vacuum booster hose to the power brake booster check valve and secure with the clamp. Make sure the vacuum booster hose is routed as shown.

Install the brake master cylinder push rod spacers and position the stoplight switch on the end of the brake pedal-to-power brake booster push rod from inside the cab. Then install the stoplight switch and brake pedal-to-power brake booster push rod on the brake pedal pin, along with brake master cylinder push rod bushings on each side, and secure with the self-locking pin.

Connect the stoplamp switch wiring.

Reconnect battery ground cable.

Start the engine (6007) and check brake operation.
.............
Brake Booster Vacuum Hose Routing




Item Part Number Description
1 19867 Air Conditioning Hose
2 381298 Vacuum Hose
3 382984 Clamp
4 2365 Power Brake Booster Check Valve
5 9600 Engine Air Cleaner
6 2140 Brake Master Cylinder
7 2005 Power Brake Booster
8 9A474 Intake Manifold Vacuum Outlet Fitting and Cap
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my broncolinks.com was "disturbed"; but some sections are archived @ [url]http://web.archive.org/web/20121009110424/http://www.broncolinks.com/index.php
select a LINK, Right Click & Hit Properties; copy the second HTTP address; paste in a new browser window or Tab to see original page
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Old 10-04-2010, 02:06 PM   #10
jam0o0
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holy huge information post. THANK YOU. off to the parts store i got for a new booster. this should give me an opportunity to get the booster-master pushrod length exactly right. and make the truck fun to drive again.
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'93 F250 7.3 turbo, ZF5, 2wd, excab, long bed.
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Old 10-04-2010, 04:17 PM   #11
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I had that problem with a mustang. I replaced the booster and it was fixed. Fluid had leaked from the master cylinder and messed up the booster.
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Old 10-21-2010, 10:34 AM   #12
jam0o0
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I forgot to update this. a new booster fixed the problem i adjusted the pushrod and now my brakes are better than ever.

the old booster rod that goes to the pedal was rusting really bad inside the felt 'seal'. any idea how that would happen?

thanks again for all the help.
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'93 F250 7.3 turbo, ZF5, 2wd, excab, long bed.
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Old 10-21-2010, 11:30 AM   #13
Apache0715
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I just replaced my old booster and it did the exact same thing. the road was so rusted it was about to snap. The booster wasn't that old either. When I put a new one on I put some rtv between the booster and the firewall to help seal it and keep water out, hopefully it wont happen again.
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Old 10-21-2010, 02:34 PM   #14
miesk5
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yo pal,
Glad to share the real-deal info from Ford!
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THANKS to ALL WHO SERVE!

my broncolinks.com was "disturbed"; but some sections are archived @ [url]http://web.archive.org/web/20121009110424/http://www.broncolinks.com/index.php
select a LINK, Right Click & Hit Properties; copy the second HTTP address; paste in a new browser window or Tab to see original page
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Old 10-23-2010, 05:36 AM   #15
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Yea bud, miesk is right.. I would replace the booster and master.. They aren't horribly expensive new and the brakes will be new again.. I had fluid drain into my booster and naturally it ruined it..
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Old 10-11-2013, 08:09 AM   #16
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I am so glad I know this site. I just had my bronco shipped down from alaska to the east coast and it had been sitting for about 7 months. I get in it and this exact problem happens. We tried swapping out the master cylinder but it kept sticking. Changing out the power booster today. There's plenty of rust build up on it but I guess that's what happens when she's got 179,000 miles on her. Thanks guys!
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Old 02-22-2014, 11:47 PM   #17
BroncoDG
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looking to replace both gas and brake pedals

I am looking to replace my pedals to custom made ones and can not seem to find a place in my city to do that and looked at some sites online and i was wondering if anyone had a recommendations where i could go for custom pedals
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