brake problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ocbaud · 02-01-2007, 09:36 PM

got the new master cylinder on and bled. all the lines are air free and have fresh fluid in them.

here is the problem i'm having. the first half of the pedal travel is nice and firm, after that, the pedal is a lot softer and the brakes begin to not work as well.

any idea what the problem could be? i know there isnt any air in the system.

Restrorob · 02-01-2007, 09:55 PM

Have you checked the shoe adjustment, That could possibly cause a lower spongy feeling pedal.

ocbaud · 02-01-2007, 09:58 PM

no i havent checked that, why would that cause it to be spongy only past half way in the travel?

also, i DO need new brakes, including the drums turned, new shoes, new rotors, and new pads. its all on my list

*rage'nrat638* · 02-01-2007, 10:08 PM

80% of the braking power comes from the front brakes
80% of the pedal height comes from the rear brake adjustment

it's very possiable you have a bad master cyl. is it new or rebuilt?

i would do as stated.. adjust up the rear brakes. bad brakes make a truck stop poorly. and the extra fluid that has to fill the lines to make up for worn brakes make the pedal funky..low

it's not uncommon to get a bad rebuilt master cyl these days

ocbaud · 02-01-2007, 10:12 PM

yeah, it was rebuilt, cause it was about $70 cheaper than new.

how would i know if it was bad or not? its not leaking like the one that WAS on there.

how do i adjust the rear brakes again? haha havent done it in a long while.

bowtiecb · 02-01-2007, 10:18 PM

have checked your wheel cyl and see if they are wet

ocbaud · 02-01-2007, 10:24 PM

Quote:

Originally Posted by bowtiecb

have checked your wheel cyl and see if they are wet

i havent, but probably will. they were both replaced about 2 years ago.

*rage'nrat638* · 02-01-2007, 10:24 PM

there a inspection hole with a rubber plug on the rear of the backing plate.
you can use a brake adjustment tool or a flat blade screw driver to adjust the star wheel in side. adjust them up till you feel a small amount of tension.
while turning the wheel- drum

not to much. or you will smoke the brakes..its a touch and feel thing.

i would just plan on doing the brakes before i went to crazy..

ocbaud · 02-01-2007, 10:27 PM

yeah....

mine doesn't have the inspection hole. found that out a few years ago when i was working on the brakes then. dunno why it doesnt, but it just doesnt have anything there, no plug, no hole, nothing but metal.

*rage'nrat638* · 02-01-2007, 10:31 PM

humm. there should be a knock out on the front of the drum or the backing plate.. may not have been removed yet

ocbaud · 02-01-2007, 10:33 PM

Quote:

Originally Posted by rage'nrat638

humm. there should be a knock out on the front of the drum or the backing plate.. may not have been removed yet

actually, i believe there is one on the drum, its about the size of wheel weight on the front of it....

*rage'nrat638* · 02-01-2007, 10:36 PM

yup thats the g spot

there should be a rubber plug with the spring hardware kit when you do your brakes

ocbaud · 02-01-2007, 10:41 PM

does this look like thats what it is???

Restrorob · 02-01-2007, 10:53 PM

No, That's a weight to balance the drum....If there is a adjuster hole in the drum it could be behind your wheel spoke.

MylilBowTie · 02-02-2007, 12:37 AM

The hole is on your backing plate that your brakes and wheel cylinder attach to. Should be at the bottom center. If you cant find it take your brake drum off and look on the backing plate around where the adjuster star is on the bottom. Should be right there.

ocbaud · 02-02-2007, 12:48 AM

Quote:

Originally Posted by MylilBowTie

The hole is on your backing plate that your brakes and wheel cylinder attach to. Should be at the bottom center. If you cant find it take your brake drum off and look on the backing plate around where the adjuster star is on the bottom. Should be right there.

like i said, its not there, at all. i've checked every time i do brake work on it, there is no adjusting hole, i think i posted pics before the board was redone a couple years ago.

**N2TRUX** · 02-02-2007, 12:51 AM

I don't think you have an adjustment issue. If your pedal is spongy at the bottom it sounds like you either have air in the system or the master cylinder is blown internally. New, or rebuilt it could be bad. Don't fix what ain't broke...

ocbaud · 02-02-2007, 01:01 AM

yeah, like i said, i'll bleed it all again this weekend, its all new fluid so i can reuse what i pump out

if that doesnt work, i'll go try another mc

i'm just happy that its "drivable" again

got insurance put back on it today and bought a new battery so i could get it started. today was the first time in like 3 months i've drove it and the first time in 1 1/2 months that its been started.

ocbaud · 02-02-2007, 01:41 AM

well hot damn

priced everything out through napa for all the parts i'm wanting to get

new rotors
new pads
new drums
new shoes
2 new calipers
drum hardware kit

comes to almost $300

i know it needs done though

Eyegore · 02-02-2007, 11:37 AM

Do you have a proportioning valve? On my old blazers(77-80)I had to compress the valve on its side to properly bleed the system or I would have the same thing happen that your dealing with. Also do you have a newer rearend? that would answer why there is no adjustment opening on the backing plate, at least my 99 suburban did not have one.

ocbaud · 02-02-2007, 12:46 PM

no, its the stock rear end

what exactly do i need to do with the prop. valve to bleed it correctly?

boxrodz · 02-02-2007, 01:45 PM

I also believe that you still have air in the system (or that you have a leak in the MC, Wheel Cylinder, Line/Fittings).

Here's a pic of the combination valve that Eyegore is referring:

Depress the metering pin while performing the bleeding of the brakes. I wedged a block of wood to depress it.

A bit more information is here: http://67-72chevytrucks.com/vboard/s...d.php?t=216639

ocbaud · 02-03-2007, 05:14 PM

ok, i checked it out while angie was hitting the brakes, the metering pin is letting a little bit of fluid out of it whenever she hits the brakes.

as in, she'll hit the brakes, the pin will pop out and fluid will come out with it.....

ocbaud · 02-07-2007, 12:03 AM

think its under control now

bled the master cylinder again the other day and drove it a little tonight and the pedal is consistent the whole way through. i just need to bleed the lines at the wheels one more time and they should all be good to go

boxrodz · 02-08-2007, 12:51 AM

Quote:

Originally Posted by ocbaud

think its under control now

bled the master cylinder again the other day and drove it a little tonight and the pedal is consistent the whole way through. i just need to bleed the lines at the wheels one more time and they should all be good to go

Good to hear.

It took me a few times to completely bleed the air from the system when I rebuilt my brakes.

02-01-2007, 09:36 PM	#1
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	brake problem got the new master cylinder on and bled. all the lines are air free and have fresh fluid in them. here is the problem i'm having. the first half of the pedal travel is nice and firm, after that, the pedal is a lot softer and the brakes begin to not work as well. any idea what the problem could be? i know there isnt any air in the system.

02-01-2007, 09:55 PM	#2
Restrorob The One And Only !!! Join Date: Jan 2007 Location: Hole in the woods Florida Posts: 4,567	Re: brake problem Have you checked the shoe adjustment, That could possibly cause a lower spongy feeling pedal. __________________ 93 Jeep XJ 88 Buick La Sabra Toys; 88 TA-GTA in the works.... 97 GMC Ext. Cab 502 Crate 5 Spd......Sucks Gas But Haulz Azz ! The primary function of an Engineer is to make it difficult for the Fabricator and impossible for the Mechanic. *"Why go out preserved when you can go out beat up, worn out, sliding in sideways screaming, Holy Sh!t What A Ride" !!!*

02-01-2007, 09:58 PM	#3
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	Re: brake problem no i havent checked that, why would that cause it to be spongy only past half way in the travel? also, i DO need new brakes, including the drums turned, new shoes, new rotors, and new pads. its all on my list

02-01-2007, 10:08 PM	#4
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	Re: brake problem 80% of the braking power comes from the front brakes 80% of the pedal height comes from the rear brake adjustment it's very possiable you have a bad master cyl. is it new or rebuilt? i would do as stated.. adjust up the rear brakes. bad brakes make a truck stop poorly. and the extra fluid that has to fill the lines to make up for worn brakes make the pedal funky..low it's not uncommon to get a bad rebuilt master cyl these days

02-01-2007, 10:12 PM	#5
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	Re: brake problem yeah, it was rebuilt, cause it was about $70 cheaper than new. how would i know if it was bad or not? its not leaking like the one that WAS on there. how do i adjust the rear brakes again? haha havent done it in a long while.

02-01-2007, 10:18 PM	#6
bowtiecb Registered User Join Date: Oct 2006 Location: alabama Posts: 79	Re: brake problem have checked your wheel cyl and see if they are wet

02-01-2007, 10:24 PM	#8
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	Re: brake problem there a inspection hole with a rubber plug on the rear of the backing plate. you can use a brake adjustment tool or a flat blade screw driver to adjust the star wheel in side. adjust them up till you feel a small amount of tension. while turning the wheel- drum not to much. or you will smoke the brakes..its a touch and feel thing. i would just plan on doing the brakes before i went to crazy.. Last edited by rage'nrat638; 02-01-2007 at 10:25 PM.

02-01-2007, 10:27 PM	#9
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	Re: brake problem yeah.... mine doesn't have the inspection hole. found that out a few years ago when i was working on the brakes then. dunno why it doesnt, but it just doesnt have anything there, no plug, no hole, nothing but metal.

02-01-2007, 10:31 PM	#10
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	Re: brake problem humm. there should be a knock out on the front of the drum or the backing plate.. may not have been removed yet

02-01-2007, 10:36 PM	#12
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	Re: brake problem yup thats the g spot there should be a rubber plug with the spring hardware kit when you do your brakes

02-01-2007, 10:41 PM	#13
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	Re: brake problem does this look like thats what it is???

02-01-2007, 10:53 PM	#14
Restrorob The One And Only !!! Join Date: Jan 2007 Location: Hole in the woods Florida Posts: 4,567	Re: brake problem No, That's a weight to balance the drum....If there is a adjuster hole in the drum it could be behind your wheel spoke. __________________ 93 Jeep XJ 88 Buick La Sabra Toys; 88 TA-GTA in the works.... 97 GMC Ext. Cab 502 Crate 5 Spd......Sucks Gas But Haulz Azz ! The primary function of an Engineer is to make it difficult for the Fabricator and impossible for the Mechanic. *"Why go out preserved when you can go out beat up, worn out, sliding in sideways screaming, Holy Sh!t What A Ride" !!!* Last edited by Restrorob; 02-01-2007 at 10:55 PM.

02-02-2007, 12:37 AM	#15
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	Re: brake problem The hole is on your backing plate that your brakes and wheel cylinder attach to. Should be at the bottom center. If you cant find it take your brake drum off and look on the backing plate around where the adjuster star is on the bottom. Should be right there. __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

02-02-2007, 12:51 AM	#17
N2TRUX Happy to be here Join Date: Mar 2000 Location: Cypress, TX Posts: 39,021	Re: brake problem I don't think you have an adjustment issue. If your pedal is spongy at the bottom it sounds like you either have air in the system or the master cylinder is blown internally. New, or rebuilt it could be bad. Don't fix what ain't broke... __________________ Follow me on Facebook and Instagram @N2trux.com Articles- "Jake" the 84 to 74 crewcab "Elwood" the77_Remix 85 GMC Sierra "Scarlett" "Refining Sierra"

02-02-2007, 01:01 AM	#18
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	Re: brake problem yeah, like i said, i'll bleed it all again this weekend, its all new fluid so i can reuse what i pump out if that doesnt work, i'll go try another mc i'm just happy that its "drivable" again got insurance put back on it today and bought a new battery so i could get it started. today was the first time in like 3 months i've drove it and the first time in 1 1/2 months that its been started.



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02-02-2007, 01:41 AM	#19
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	Re: brake problem well hot damn priced everything out through napa for all the parts i'm wanting to get new rotors new pads new drums new shoes 2 new calipers drum hardware kit comes to almost $300 i know it needs done though

02-02-2007, 11:37 AM	#20
Eyegore What Hump? Join Date: Apr 2003 Location: New River AZ Posts: 2,009	Re: brake problem Do you have a proportioning valve? On my old blazers(77-80)I had to compress the valve on its side to properly bleed the system or I would have the same thing happen that your dealing with. Also do you have a newer rearend? that would answer why there is no adjustment opening on the backing plate, at least my 99 suburban did not have one. __________________ Lil red 86 c-10 99 Sub 78 Camper Special w/ 454

02-02-2007, 12:46 PM	#21
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	Re: brake problem no, its the stock rear end what exactly do i need to do with the prop. valve to bleed it correctly?

02-02-2007, 01:45 PM	#22
boxrodz Until Seventy Times Seven Join Date: Feb 2005 Location: Rocky Mountain Front Range Posts: 1,301	Re: brake problem I also believe that you still have air in the system (or that you have a leak in the MC, Wheel Cylinder, Line/Fittings). Here's a pic of the combination valve that Eyegore is referring: Depress the metering pin while performing the bleeding of the brakes. I wedged a block of wood to depress it. A bit more information is here: http://67-72chevytrucks.com/vboard/s...d.php?t=216639 __________________ boxRODz 1983 C10 SWB Fleetside When two halves is gone, there's nuthin left. Two nothings is nuthin. That's mathematics son. You can argue with me but you can't argue with figures. Two half nothings is a whole nuthin...

02-03-2007, 05:14 PM	#23
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	Re: brake problem ok, i checked it out while angie was hitting the brakes, the metering pin is letting a little bit of fluid out of it whenever she hits the brakes. as in, she'll hit the brakes, the pin will pop out and fluid will come out with it.....

02-07-2007, 12:03 AM	#24
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	Re: brake problem think its under control now bled the master cylinder again the other day and drove it a little tonight and the pedal is consistent the whole way through. i just need to bleed the lines at the wheels one more time and they should all be good to go

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