Why is the brake pedal going to the floor? - Diesel Forum - TheDieselStop.com
Ford Diesel Forum / Powerstroke Forum
Ford Diesel Forum / Powerstroke Forum
Go Back   Diesel Forum - TheDieselStop.com > Ford Diesels > 7.3L IDI Diesels (Not Power Strokes)

7.3L IDI Diesels (Not Power Strokes) Technical discussion of topics related to vehicles powered by the 7.3 Liter In-Direct Injection Navistar engines.

TheDieselstop.com is the premier Diesel Truck Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools Display Modes
Old 03-08-2005, 12:18 AM   #1 (permalink)
Senior Member
 
Join Date: Sep 2002
Location: Cool, PRK (aka CA)
Posts: 100
My Photos: (1)
Feedback Score: 0 reviews
Why is the brake pedal going to the floor?

Started out replacing a hissing brake booster.
Looked at the master cylinder, & said, "Hmmm...looks old, better replace it too."
Then, I really screwed up & decided to replace both front calipers with Kragen's finest rebuilt units.
After bench bleeding the master cylinder, & going through 1.5 quarts bleeding all four wheels, the pedal still was slowly going to the floor.
LF caliper was leaking at the copper banjo bolt washers; retightening fixed that.
Checked the RF caliper for leaks; none found.
With the engine running, I pressed the brake pedal several times slowly to the floor, and re-inspected all four wheels & crawled under the length of the truck for fluid leaks; agian, none found.
Pedal feel will "firm up" after quickly pumping the pedal a few times, but will go to the floor when applying continuous pressure.

At this point, I'm assuming the new/rebuilt master cylinder is defective.
So, before I look for the answer in a bottle of Maker's Mark, any of y'all got any ideas?

Thanks
__________________
1994 F350 4x4 E4OD Crew Cab Dually Factory Turbocharged mit ATS Intercooler Kit.
The_Real_Oaf is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 03-08-2005, 02:57 AM   #2 (permalink)
Senior Member
 
Join Date: Mar 2005
Location: wasilla, alaska
Posts: 277
My Photos: (0)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

i was trying to find a fix for your problem and refered to my chilton's manual, (not the best, but the exploded views are nice) and the manual mentioned the brake booster pushrod adjustment"BRAKES 9-5"

It stated

"The pushrod has an adjustment screw to maintain the correct relationship between the booster control valve plunger and the master cylinder piston. Too long ... cause brakes to drag, Too short it will cause excessive pedal travel and an undesirable clunk in the booster area.

The adjustment screw should be .995 of an inch from the master cylinder mounting surface.

If you dont have access to the lit let me know and i can get it to you via email.
__________________
91 f-350, dually, 7.3 diesel. 2wd, 4.10 gears LS. E4OD. New injectors, lift pump, and fuel filter at current 85,000 miles. Autometer pyro and fuel turned up. 3" exhaust with walker "btm" muffler
http://community.webshots.com/user/olivera_149
olivera149 is offline   Reply With Quote Quick reply to this message
Old 03-08-2005, 08:44 AM   #3 (permalink)
Senior Member
 
cdnsarguy's Avatar
 
Join Date: Jan 2003
Location: Neepawa, Manitoba Canada
Posts: 20,672
My Photos: (109)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

[ QUOTE ]
At this point, I'm assuming the new/rebuilt master cylinder is defective.


[/ QUOTE ]

You hit the nail on the head.
__________________
93 F250 7.3 IDI S/C XLT 4X4 E40D 3.55LS, Captains chairs, Tutone Mocha, Leer 48" Hiboy cap, FR & RR hitches, full DeeZee running boards. Factory ordered/delivered Jan 93

Toys: 2006 37' Triple E Embassy coach (powered by Cummins), 18' Sylvan Pro Fish with Mariner motors.

Proud Canadian BOOB man too!!

Please PRIVATE MESSAGE only!! ...
Please DO NOT.....visitor message me...
cdnsarguy is offline   Reply With Quote Quick reply to this message
Old 03-08-2005, 09:42 AM   #4 (permalink)
Senior Member
 
Join Date: Sep 2002
Location: Cool, PRK (aka CA)
Posts: 100
My Photos: (1)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

[ QUOTE ]

The adjustment screw should be .995 of an inch from the master cylinder mounting surface.

If you dont have access to the lit let me know and i can get it to you via email.

[/ QUOTE ]

Thanks for the offer, but the rod has been properly adjusted.
__________________
1994 F350 4x4 E4OD Crew Cab Dually Factory Turbocharged mit ATS Intercooler Kit.
The_Real_Oaf is offline   Reply With Quote Quick reply to this message
Old 03-08-2005, 10:13 AM   #5 (permalink)
Senior Member
 
Join Date: Aug 1999
Location: Penn Valley, Ca
Posts: 6,940
My Photos: (9)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

A slim possibility is that the RABS valve is leaking into the accumulator also. But it would not make sense in the sequence of events. But it is possible. The way to check is to let the pedal sink, then pick it up and give it another stab and hold again. If it is the RABS valve the sinking will stop when the accumulator gets full. If it is the MC it will continue to sink no matter how many times you re-stab the pedal.

Birken
Birken Vogt is offline   Reply With Quote Quick reply to this message
Old 03-08-2005, 01:32 PM   #6 (permalink)
Senior Member
 
Join Date: Jul 2004
Location: Huntsville, AL
Posts: 474
My Photos: (0)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

Is the pedal not supposed to go to the floor with the engine running? Most cars and trucks I have driven the booster will give you enough boost to push the pedal to the floor. Also I have found out that with the engine at idle on my F350 that I have about one good stab at the brakes then the pedal gets hard from lack of boost. What bothers me is when you push the pedal all the way to the floor and you don't lock the brakes, which seems to be the case with most of these big Ford trucks. I found out on the way back from Florida that my brakes did not work well when I had to apply them and let off and apply them again with the engine at low RPM. I mean they are not great when there is boost. Sometimes I think that dragging my feet would work better. If the pedal sinks to the floor with the engine off I would be more worried. I have to agree with the others though. Probably a bad master cylinder. I have not checked the booster pin clearance yet maybe I will do that soon.

Perry
perryg114 is offline   Reply With Quote Quick reply to this message
Old 03-08-2005, 01:53 PM   #7 (permalink)
Senior Member
 
cdnsarguy's Avatar
 
Join Date: Jan 2003
Location: Neepawa, Manitoba Canada
Posts: 20,672
My Photos: (109)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

Along with Birkens post, if the new master cylinder seals are not doing their job and you gently press the pedal and it goes to the floor, then press fast with good pressure results this could also indicate the M/C is the problem. If this problem was NOT present before the changes I would suspect a changed part.
__________________
93 F250 7.3 IDI S/C XLT 4X4 E40D 3.55LS, Captains chairs, Tutone Mocha, Leer 48" Hiboy cap, FR & RR hitches, full DeeZee running boards. Factory ordered/delivered Jan 93

Toys: 2006 37' Triple E Embassy coach (powered by Cummins), 18' Sylvan Pro Fish with Mariner motors.

Proud Canadian BOOB man too!!

Please PRIVATE MESSAGE only!! ...
Please DO NOT.....visitor message me...
cdnsarguy is offline   Reply With Quote Quick reply to this message
Old 03-08-2005, 03:14 PM   #8 (permalink)
Senior Member
 
Join Date: Sep 2002
Location: Cool, PRK (aka CA)
Posts: 100
My Photos: (1)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

The pedal travel was fine before I "fixed" it [img]/ubbthreads/images/graemlins/crazy.gif[/img]; the only component that needed R&R'ing was the booster.
__________________
1994 F350 4x4 E4OD Crew Cab Dually Factory Turbocharged mit ATS Intercooler Kit.
The_Real_Oaf is offline   Reply With Quote Quick reply to this message
Old 03-08-2005, 06:58 PM   #9 (permalink)
Senior Member
 
cdnsarguy's Avatar
 
Join Date: Jan 2003
Location: Neepawa, Manitoba Canada
Posts: 20,672
My Photos: (109)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

Have you driven this vehicle yet..............since repair.
__________________
93 F250 7.3 IDI S/C XLT 4X4 E40D 3.55LS, Captains chairs, Tutone Mocha, Leer 48" Hiboy cap, FR & RR hitches, full DeeZee running boards. Factory ordered/delivered Jan 93

Toys: 2006 37' Triple E Embassy coach (powered by Cummins), 18' Sylvan Pro Fish with Mariner motors.

Proud Canadian BOOB man too!!

Please PRIVATE MESSAGE only!! ...
Please DO NOT.....visitor message me...
cdnsarguy is offline   Reply With Quote Quick reply to this message
Old 03-09-2005, 07:52 AM   #10 (permalink)
Senior Member
 
Join Date: Jul 2004
Location: Huntsville, AL
Posts: 474
My Photos: (0)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

Pete has a point there about driving the truck. Sometimes it takes a while for things to seat in and work right. Also have you checked the adjustment of the rear brakes. Not sure how they could have gotten out of adjustment but might as well cover all the bases. My brakes are not great and I have not had time to hunt all the bugs and I don't have a truck with good brakes to compare with. Did you bench bleed the new master cylinder before installing the lines? If you have a way of blocking off the ports on the master and then if it still leaks down you know where the problem is.

Perry
perryg114 is offline   Reply With Quote Quick reply to this message
Old 03-09-2005, 09:36 AM   #11 (permalink)
Senior Member
 
cdnsarguy's Avatar
 
Join Date: Jan 2003
Location: Neepawa, Manitoba Canada
Posts: 20,672
My Photos: (109)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

As stated in the first post.......

[ QUOTE ]
Started out replacing a hissing brake booster.


[/ QUOTE ]

I feel the problem may be the rubber reaction disc in the booster may be out of place, the only symptom it has in this case is very low pedal but severe brake reaction at the last minute...."read put you through the windshield: [img]/ubbthreads/images/graemlins/eek.gif[/img]

If the master cylinder pushrod is inadvertently/purposely removed from the booster this will be the result when/if the disc falls out of place inside the booster.
__________________
93 F250 7.3 IDI S/C XLT 4X4 E40D 3.55LS, Captains chairs, Tutone Mocha, Leer 48" Hiboy cap, FR & RR hitches, full DeeZee running boards. Factory ordered/delivered Jan 93

Toys: 2006 37' Triple E Embassy coach (powered by Cummins), 18' Sylvan Pro Fish with Mariner motors.

Proud Canadian BOOB man too!!

Please PRIVATE MESSAGE only!! ...
Please DO NOT.....visitor message me...
cdnsarguy is offline   Reply With Quote Quick reply to this message
Old 03-09-2005, 12:19 PM   #12 (permalink)
Senior Member
 
Join Date: Sep 2002
Location: Cool, PRK (aka CA)
Posts: 100
My Photos: (1)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

Checked the situation again last night & test drove the truck around the neighborhood.
No change in pedal feel.
Exchanged the alleged defective mater cylinder & the pedal feel slowly improved, but I feel that the pedal travels too far.
Also, the red "BRAKE" light came on for awhile. Checked the fluid (again) & it was OK.
Drove the truck for 6 miles, to go vote, and the light went out.

One more symptom that's reared it's ugly head since I started working on it is that I can't shift out of Park with the engine running.
BTW, the electrical switch that screws into the MC is cruise control related, but applying the brakes does not "pause" the cruise control.

But to respond to cdnsarguy post, the booster pushrod is in place and has been adjusted correctly.
Of course, I had to find out the hard way that this rod is not adjusted by the reman company by bolting everything & almost going through the windshield! [img]/ubbthreads/images/graemlins/phoney.gif[/img] [img]/ubbthreads/images/graemlins/shocked.gif[/img]

Angain, thanks for all the info/help

Paul
__________________
1994 F350 4x4 E4OD Crew Cab Dually Factory Turbocharged mit ATS Intercooler Kit.
The_Real_Oaf is offline   Reply With Quote Quick reply to this message
Old 03-09-2005, 01:31 PM   #13 (permalink)
Senior Member
 
cdnsarguy's Avatar
 
Join Date: Jan 2003
Location: Neepawa, Manitoba Canada
Posts: 20,672
My Photos: (109)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

Paul I still believe you have the wrong Booster od you have adjusted for the loss of the reaction disc.

Here is some other info that may be pertinent.

1997 and earlier diesel trucks equiped with vacuum power brakes--Low/creeping pedal:
Many owners have complained of a low or creeping brake pedal on their trucks, often mistaken for a bad master cylinder or Rear ABS valve. If the condition occurs after the vehicle has come to a stop, and no other brake concerns are found, (worn or out-of-adjusted brakes, cocked pads, or hydraulic problems) the condition is normal and the result of the vacuum pump replenishing the vacuum inside the power booster. Ford has developed a Zero-Loss Travel brake booster to correct this condition if the customer finds it unacceptable. This part is only for use on diesel-equiped trucks--P/N F5TZ-2005-CA--and is not a service replacement; it must be ordered by the part number, not vehicle application.

This condition is similar to the low brake pedal concern on all 1995 F-series that required a larger-diameter master cylinder:

Trucks without cruise control:


F6TZ-2140-AB
F-250 Gas 4X2; F-350 DRW, SRW Gas 4X2, SRW 7.3 4X2 168" WB
F6TZ-2140-EB
F-250 4X4, 7.3 4X2; F-350 SRW 4X4, SRW 7.3 4X2 133" WB

Trucks with cruise control:
F6TZ-2140-BA
F-250 Gas 4X2; F-350 DRW, SRW Gas 4X2, SRW 7.3 4X2 168" WB
F6TZ-2140-FB
F-250 4X4, 7.3 4X2; F-350 SRW 4X4, SRW 7.3 4X2 133" WB

These part numbers are from TSB's 96-25-19 and 98-5A-34, and are not normal service-stock replacment parts.
__________________
93 F250 7.3 IDI S/C XLT 4X4 E40D 3.55LS, Captains chairs, Tutone Mocha, Leer 48" Hiboy cap, FR & RR hitches, full DeeZee running boards. Factory ordered/delivered Jan 93

Toys: 2006 37' Triple E Embassy coach (powered by Cummins), 18' Sylvan Pro Fish with Mariner motors.

Proud Canadian BOOB man too!!

Please PRIVATE MESSAGE only!! ...
Please DO NOT.....visitor message me...
cdnsarguy is offline   Reply With Quote Quick reply to this message
Old 03-09-2005, 01:43 PM   #14 (permalink)
Senior Member
 
Join Date: Dec 2003
Location: NE Kansas
Posts: 1,946
My Photos: (0)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

all of the problems you describe can be caused by out of adjustment rear brakes, but I cannot figure out how it would ahve magically happened, unless the booster was bad and you didn't notice the low travel because of the hard pedal.

Low brakes are cause by an out of adjustment rear brake because the rear brakes apply before the front, due to the different types of brake design. Excessive pedal travel causes the vacuum pump to move more air, making that light come on. I think that is a side effect of the real problem. Also, air in the line, or a leaky or ruptured line can cause it. THese would be in the back part of the circuit.
__________________
2006 GMC K3500 CC DRW 4x4
1994 F-350 DRW PS w/ zf5
1996 Town Car
mgraveman is offline   Reply With Quote Quick reply to this message
Old 03-10-2005, 01:34 AM   #15 (permalink)
Senior Member
 
Join Date: Sep 2002
Location: Cool, PRK (aka CA)
Posts: 100
My Photos: (1)
Feedback Score: 0 reviews
Re: Why is the brake pedal going to the floor?

The pedal seems to have magically improved overnight; while it doesn't "feel" 100%, maybe it's me.
I'll drive it to work tomarrow & see if anything changes.
__________________
1994 F350 4x4 E4OD Crew Cab Dually Factory Turbocharged mit ATS Intercooler Kit.
The_Real_Oaf is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

  Diesel Forum - TheDieselStop.com > Ford Diesels > 7.3L IDI Diesels (Not Power Strokes)

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Diesel Forum - TheDieselStop.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
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
Display Modes

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



Wheel & Tire Center

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 03:35 PM.



Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.