The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 12-14-2014, 02:31 PM   #1
mpierce9
Registered User
 
Join Date: Nov 2013
Location: ATLANTA
Posts: 223
Soft Brakes (pedal to floor)

Hello - Been working on this a month and have exhausted all the options I have found in these forums. 1975 Chevy blazer disc front, drum rear.

My brake pedal travels to the floor before stopping. Slamming the brake pedal to the floor at about 30 MPH takes about 30-40 yards to come to a complete stop.

The pedal also returns slowly after being applied.


Done so far:
Overall System:
  • I've been through two master cylinders (I've bench bleed both extensively)
  • I want to clarify that I "pumped" each MC up to 150 times and saw zero air bubbles
  • New brake booster
  • Extended pedal link to booster to engage the booster immediately
  • Resolved all leaks
  • Bleed the entire system multiple times with the "One person pumps the pedal five times and holds it down, while the other person opens the bleeder" resulting in no visible air bubbles.
  • Confirmed the Combination / Proportioning valve is working as expected (i.e. the light isn't on)

Front brakes:
  • Replaced both calipers, discs & rotors
  • Replaced both soft brake hoses, banjo bolts and washers

Rear brakes:
  • Replaced both wheel cylinders
  • Tightened both shoes to sit very close the drum

General notes
  • Each bleeder has excellent fluid flow when bleeding
  • With the engine powered off, the brake pedal returns quickly
  • With the engine powered on, the brake pedal returns slower
  • Feels like most of the braking is being done by the rear brakes
  • This started with a bad wheel cylinder resulting in my proportioning valve becoming tripped
  • On the MC I plugged the ports and attempted to press the brake pedal down this resulted in a completely firm & unmovable brake pedal (which I believe indicates the MC has been properly bleed and is working as expected.

Any help or direction would be greatly appreciated. Minus the hard lines, and Combination/Prop valve almost everything has been replaced.
mpierce9 is offline   Reply With Quote
Old 12-14-2014, 04:15 PM   #2
donut
Registered User
 
donut's Avatar
 
Join Date: Aug 2009
Location: S.C.
Posts: 1,593
Re: Soft Brakes (pedal to floor)

Seems to me that there's either more air or a leak. Loosing any fluid?
If using a helper, only push the brake pedal once, then while they're holding it down, crack the bleeder. Pushing the pedal 5 times may be aerating the fluid.

I usually do it myself, but I have a small bottle (brake bleeder kit) Tubing goes from the bleeder screw, under the fluid level in the small bottle. That way your pushing out air, and not taking the chance of introducing air in through the bleeder screw.
__________________
'86 C-30 dually, 454/tbh400
'73 K-20 350/350/205 (sold )

I'm kinda like duct tape- no real purpose, but handy to have around.
donut is offline   Reply With Quote
Old 12-14-2014, 07:39 PM   #3
hatzie
Moderator
 
hatzie's Avatar
 
Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,911
Re: Soft Brakes (pedal to floor)

Don't pump the pedal between opening the bleeders it aerates the fluid making air pockets that will not work out.
Push the pedal down with the bleeder open and then close the bleeder before the assistant lets off the pedal.

You can build one of these or buy one. I built one and bought a Master Cylinder cover from Motive Power. Makes one man bleed jobs a piece of cake.
http://www.amazon.com/Motive-Products-105-System-B... http://www.amazon.com/Motive-Products-105-System-B...
Use a C-Clamp to hold the cover on, if you can find a place to put it, rather than the Rube Goldberg J-Hook and Chain arrangement that comes with the Motive Power cover.
__________________
1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8


RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.

Last edited by hatzie; 12-14-2014 at 07:44 PM.
hatzie is offline   Reply With Quote
Old 12-14-2014, 08:00 PM   #4
86c20
Registered User
 
86c20's Avatar
 
Join Date: Mar 2012
Location: edgartown mass
Posts: 852
Re: Soft Brakes (pedal to floor)

sounds like the ford i had. try bleeding with it running
__________________
1986 c20 "the hillbilly" 350 sm465 3.42gears 21mpg at 70mph
1985 k30 "the ice cream truck from hell" no rust az truck
197-8??? c30 "ramp truck" 454
1978 monte carlo 350 350th with 2.73 gears. no rust. sc car
86c20 is offline   Reply With Quote
Old 12-14-2014, 09:16 PM   #5
hatzie
Moderator
 
hatzie's Avatar
 
Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,911
Re: Soft Brakes (pedal to floor)

One thing nobody usually mentions is to start with the longest tube run first and work your way to the shortest.
On the squares this is usually the Left Rear Wheel Cylinder and then RR then RF caliper then LF...
__________________
1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8


RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.
hatzie is offline   Reply With Quote
Old 12-14-2014, 10:10 PM   #6
sgr60
Registered User
 
Join Date: Nov 2014
Location: CT
Posts: 105
Re: Soft Brakes (pedal to floor)

I thought the procedure was push the pedal down, open the bleeder, close the bleeder, then release the pedal? That's how I always did it...

Wouldn't opening the bleeder with the pedal not depressed allow air in?
__________________
'84 K20 350/465/208
sgr60 is offline   Reply With Quote
Old 12-14-2014, 10:23 PM   #7
mrolds88
Registered User
 
Join Date: Jul 2011
Location: WV
Posts: 946
Re: Soft Brakes (pedal to floor)

Quote:
Originally Posted by sgr60 View Post
I thought the procedure was push the pedal down, open the bleeder, close the bleeder, then release the pedal? That's how I always did it
Thats the way I do it. Now if you have someone else there that is mechanically inclined, your helper can lightly hold their finger over the bleeder and it acts as a one way valve.

When you do push the pedal, do it slowly and to its full stroke.
__________________
72 GMC C2500 402/Th400 first truck (still have)
77 GMC C3500 CC dually Sold
70 C50 dump truck "Rusty"
87 K10 Suburban Sold
93 K2500 xcab 6.5TD
96 GMC K2500 Suburban 6.5 TD
mrolds88 is offline   Reply With Quote
Old 12-14-2014, 10:45 PM   #8
lahnen
Registered User
 
Join Date: Feb 2011
Location: cassadaga, ny
Posts: 28
Re: Soft Brakes (pedal to floor)

had similar issue with my suburban last year, one of my lines to the prop. valve had just a slight leak(bad flare job) had no visible air when I bled the system but wasn't getting a lot of pressure when I opened the bleeders up.
lahnen is offline   Reply With Quote
Old 12-15-2014, 08:57 AM   #9
mpierce9
Registered User
 
Join Date: Nov 2013
Location: ATLANTA
Posts: 223
Re: Soft Brakes (pedal to floor)

Is there such a thing as a pressure gauge that screws into the bleed valve spot?
mpierce9 is offline   Reply With Quote
Old 12-15-2014, 09:14 AM   #10
enaberif
Registered User
 
Join Date: Jan 2009
Location: Calgary, AB
Posts: 1,181
Re: Soft Brakes (pedal to floor)

When was the last time the master cylinder was changed out? My pedal goes right to the floor and I know for fact my master cylinder is to blame.
enaberif is offline   Reply With Quote
Old 12-15-2014, 07:30 PM   #11
mpierce9
Registered User
 
Join Date: Nov 2013
Location: ATLANTA
Posts: 223
Re: Soft Brakes (pedal to floor)

MC has been changed twice in the last 30 days. MC testest to be working well.
mpierce9 is offline   Reply With Quote
Old 12-15-2014, 10:09 PM   #12
hatzie
Moderator
 
hatzie's Avatar
 
Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,911
Re: Soft Brakes (pedal to floor)

Quote:
Originally Posted by sgr60 View Post
I thought the procedure was push the pedal down, open the bleeder, close the bleeder, then release the pedal? That's how I always did it...

Wouldn't opening the bleeder with the pedal not depressed allow air in?
I should've added "Only open the bleeder after you tell your assistant to push the pedal down." I mistakenly figured that was self explanatory.
__________________
1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8


RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.
hatzie is offline   Reply With Quote
Old 12-16-2014, 05:34 AM   #13
donut
Registered User
 
donut's Avatar
 
Join Date: Aug 2009
Location: S.C.
Posts: 1,593
Re: Soft Brakes (pedal to floor)

Not self explanatory, but I did mention it. However, I didn't mention to close it again before you release the pedal...
Of course the OP didn't ask for a step by step procedure.
__________________
'86 C-30 dually, 454/tbh400
'73 K-20 350/350/205 (sold )

I'm kinda like duct tape- no real purpose, but handy to have around.
donut is offline   Reply With Quote
Old 06-14-2019, 12:43 AM   #14
spspspspoon
Registered User
 
Join Date: Sep 2018
Location: New Orleans
Posts: 30
Re: Soft Brakes (pedal to floor)

tube on bleeder
"Quick Bleed" between the 2 hoses
usually seen on race bikes
it IS a 1 way check valve but IS a bleeder valve
also u can do like we do in VW
put valve stem like a tire(one with threads and O rings)
and place it In the top
then pressurize
spspspspoon is offline   Reply With Quote
Old 06-14-2019, 09:28 PM   #15
WyattTX
Registered User
 
Join Date: Nov 2015
Location: Down south
Posts: 518
Re: Soft Brakes (pedal to floor)

Does the pedal feel harder with the engine off?
WyattTX is offline   Reply With Quote
Old 06-15-2019, 06:21 AM   #16
WyattTX
Registered User
 
Join Date: Nov 2015
Location: Down south
Posts: 518
Re: Soft Brakes (pedal to floor)

I don't know if a GM booster has an adjustable push rod, but this would be worth looking into: https://www.google.com/amp/s/techtal...%3fhs_amp=true

If the booster push rod is too long or too short (very possible in today's low standards of manufacturing) you'll never get get a hard pedal with the engine running. If you have no air in your system, and still have a soft pedal, this is a likely culprit.
WyattTX is offline   Reply With Quote
Old 06-15-2019, 01:37 PM   #17
hatzie
Moderator
 
hatzie's Avatar
 
Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,911
Re: Soft Brakes (pedal to floor)

Quote:
Originally Posted by WyattTX View Post
I don't know if a GM booster has an adjustable push rod, but this would be worth looking into: https://www.google.com/amp/s/techtal...%3fhs_amp=true

If the booster push rod is too long or too short (very possible in today's low standards of manufacturing) you'll never get get a hard pedal with the engine running. If you have no air in your system, and still have a soft pedal, this is a likely culprit.
Chinese garbage parts that don't meet any reasonable spec poisoning the supply chain...

If you want a real exercise in futility... Try buying ball joints and tie rod ends that last more than 5,000-10,000 miles.
Wheel bearings are another fun excursion into pulling out gobs of your hair.
__________________
1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8


RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.
hatzie is offline   Reply With Quote
Old 06-15-2019, 01:54 PM   #18
kwmech
Senior Member
 
Join Date: Mar 2003
Location: Colfax-California
Posts: 8,356
Re: Soft Brakes (pedal to floor)

Still bleeding the brakes after 5 years..??? damn
kwmech is offline   Reply With Quote
Old 06-15-2019, 02:04 PM   #19
WyattTX
Registered User
 
Join Date: Nov 2015
Location: Down south
Posts: 518
Re: Soft Brakes (pedal to floor)

Oops, did not realize I posted in a zombie thread. I hope OP got his brakes to work.
WyattTX is offline   Reply With Quote
Old 06-15-2019, 02:26 PM   #20
hatzie
Moderator
 
hatzie's Avatar
 
Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,911
Re: Soft Brakes (pedal to floor)

Quote:
Originally Posted by WyattTX View Post
Oops, did not realize I posted in a zombie thread. I hope OP got his brakes to work.
You posted useful relevant information on the thread subject. Don't feel too bad.
__________________
1959 M35A2 LDT465-1D SOLD
1967 Dodge W200 B383, NP420/NP201 SOLD
1969 Dodge Polara 500 B383, A833 SOLD
1972 Ford F250 FE390, NP435/NP205 SOLD
1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
1986 M1008 CUCV SOLD
2000 GMC C2500, TD6.5L, NV4500
2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263
2009 Impala SS LS4 V8


RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.
hatzie is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
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

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 04:03 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com