Brake gurus!? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

K5KRAZIE · 06-02-2005, 04:52 PM

Alright guys (n gals) I just finished the heavy parts on my recent rear disk (among other things done) swap. Problem is the pedal is low and squishy, and I'm not getting near the amount of fluid when bleading from the rear as the fronts. I recall something about a button on the proportioning valve that has to be depressed? I know theres air in the system just need to get it out so I can go have some fun. Already missed the holiday weekend with the K5 cause of this, don't want to miss any more fun stuff.

HELP ME!

67ChevyRedneck · 06-02-2005, 05:00 PM

A stock proportioning valve may not work with a disk brake rear. It may be sending too much fulid up front and not enough out back. I've never done this before, but that would be my guess. Did you buy a kit for the rear brakes? Was there an option to buy a proportioning valve?

Faster_than_you · 06-02-2005, 05:04 PM

master cylinder.

K5KRAZIE · 06-02-2005, 05:05 PM

Forgot to say this is on my '72 K5 4wd, I just converted the front 44 to 8 lug, replaced the 12 bolt with a rear Dana 60 and the disks from a front end.
Heres some pictures to get the jucies flowing.

Furd Dana 60 with brake rotors and calipers off a front 3/4 ton Dana 44 GM.

Installed, just need to blead...

I'm going to order up a '72 3/4 ton brake booster and possibly a prop. valve. But I really wanted to get the thing working first so I could start fresh.

K5KRAZIE · 06-02-2005, 05:08 PM

Quote:

Originally Posted by Faster_than_you

master cylinder.

Brakes were fine before the swap, this is an issue with the bleading sequence being inadiquate.

smokekiki · 06-02-2005, 06:02 PM

The stock "proportioning valve"is a combination valve.It regulates the flow of the brake fluid,so that the front discs don't grab until the rear shoes contact the drum,works the brake light,and regulates how much fluid gets to the rear to prevent lock-up of the rear brakes.As far as the button,it is on the front of the valve.It needs to be depressed while bleeding the front brakes.

smokekiki · 06-02-2005, 06:10 PM

Here is a little "trouble shooting tips" reading for You...http://www.tsmmfg.com/Troubleshootin...0light%20pedal Read about the residual valve,gravity bleeding and spongy brakes.I think there is a valve in the master for the rear brakes.

fastwillie 696969 · 06-02-2005, 08:03 PM

get you a glass bottle fill it half way with brake fliud get a piece of hose to fit the bleeder valve place the hose in the bottle crack open the valve have some one pump the brakes up slowly and watch all bubbles in the jar when the bubbles stop and fluid starts to rise close the valve off remove hose then do the left side alway start off futhers away from mastercylinder

RainFade · 06-02-2005, 08:40 PM

Look on the front of the combo valve for a rubber cap it is over the thingy you depress when bleeding IIRC

K5KRAZIE · 08-09-2005, 03:00 PM

Now revisited, what the hell. I put a 3/4 ton booster on and blead all the air out. Getting the air out turned out to be more of a pain than I thought. I still think theres more in the system but it stops now. Very good upgrade IMO I think the dual diaphram booster should be on all of these trucks.

71meangreenc10 · 08-09-2005, 07:51 PM

You have to change the master cyl to one thats for disk/disk setup if you havent already, the resvoirs are different and the diameter of the piston is different. Once you do this and bleed the air out, make sure the rear calipers are in the right position to bleed, you will notice a definate improvement. Also the prop valves are different too.

Smitty

K5KRAZIE · 08-10-2005, 01:35 PM

Maybe 4wd is different my master (now 3/4 ton) is more than capable for the disks. The prop. valve has the residual valve in it for the rear drums, but the rears do not lock up before the fronts so I think I'm OK there as well.

06-02-2005, 04:52 PM	#1
K5KRAZIE Registered User Join Date: Oct 2002 Location: Wa. State Posts: 352	Brake gurus!? Alright guys (n gals) I just finished the heavy parts on my recent rear disk (among other things done) swap. Problem is the pedal is low and squishy, and I'm not getting near the amount of fluid when bleading from the rear as the fronts. I recall something about a button on the proportioning valve that has to be depressed? I know theres air in the system just need to get it out so I can go have some fun. Already missed the holiday weekend with the K5 cause of this, don't want to miss any more fun stuff. HELP ME! __________________ TRUCKS '72 K5 '06 mega dually

06-02-2005, 05:00 PM	#2
67ChevyRedneck Hittin E-Z Street on Mud Tires Join Date: Nov 2004 Location: Greenville, SC Posts: 23,090	A stock proportioning valve may not work with a disk brake rear. It may be sending too much fulid up front and not enough out back. I've never done this before, but that would be my guess. Did you buy a kit for the rear brakes? Was there an option to buy a proportioning valve? __________________ Jesse James 1967 C10 SWB Stepside: 350/700R4/3.73 1965 Ford Mustang: 289/T5-5spd/3.25 Trac-Loc 1968 Pontiac Firebird: Project Fire Chicken! 2015 Silverado Double Cab 5.3L Z71 2001 Jeep Wrangler Sport 4.0L 5spd 2020 Chevrolet Equinox Premium 2.0L Turbo 2011 Mustang V6 ~ Wife's ride American Born, Country by the Grace of God 1967 CST Shop Truck Rebuild! My 1967 C-10 Build Thread My Vintage Air A/C Install Project "On a Dime" Trying my hand at Home Renovation! 1965 Mustang Modifications!

06-02-2005, 05:04 PM	#3
Faster_than_you Registered User Join Date: Mar 2004 Location: Virginia beach, Va Posts: 209	master cylinder. __________________ ~Christopher L. Orr 71 c20, 454- Stolen While Deployed. dynoed at 550 ft lbs, 425 hp at 3000 rpm (mustang dyno). TH400 3500 stall.... etc, etc.

06-02-2005, 05:05 PM	#4
K5KRAZIE Registered User Join Date: Oct 2002 Location: Wa. State Posts: 352	Forgot to say this is on my '72 K5 4wd, I just converted the front 44 to 8 lug, replaced the 12 bolt with a rear Dana 60 and the disks from a front end. Heres some pictures to get the jucies flowing. Furd Dana 60 with brake rotors and calipers off a front 3/4 ton Dana 44 GM. Installed, just need to blead... I'm going to order up a '72 3/4 ton brake booster and possibly a prop. valve. But I really wanted to get the thing working first so I could start fresh. __________________ TRUCKS '72 K5 '06 mega dually

06-02-2005, 06:02 PM	#6
smokekiki Mike Join Date: Jan 2003 Location: west chester pa Posts: 2,473	The stock "proportioning valve"is a combination valve.It regulates the flow of the brake fluid,so that the front discs don't grab until the rear shoes contact the drum,works the brake light,and regulates how much fluid gets to the rear to prevent lock-up of the rear brakes.As far as the button,it is on the front of the valve.It needs to be depressed while bleeding the front brakes. __________________ 70'c/10, 71 suburban4x4 402bb, 72suburban 4/6 drop, 72k/5 4x4 blazer 4" lift 35 tires

06-02-2005, 06:10 PM	#7
smokekiki Mike Join Date: Jan 2003 Location: west chester pa Posts: 2,473	Here is a little "trouble shooting tips" reading for You...http://www.tsmmfg.com/Troubleshootin...0light%20pedal Read about the residual valve,gravity bleeding and spongy brakes.I think there is a valve in the master for the rear brakes. __________________ 70'c/10, 71 suburban4x4 402bb, 72suburban 4/6 drop, 72k/5 4x4 blazer 4" lift 35 tires Last edited by smokekiki; 06-02-2005 at 06:13 PM.

06-02-2005, 08:03 PM	#8
fastwillie 696969 ~Rest In Peace~ Join Date: May 2005 Location: CALIFORNIA NOR CAL Posts: 9,707	get you a glass bottle fill it half way with brake fliud get a piece of hose to fit the bleeder valve place the hose in the bottle crack open the valve have some one pump the brakes up slowly and watch all bubbles in the jar when the bubbles stop and fluid starts to rise close the valve off remove hose then do the left side alway start off futhers away from mastercylinder __________________ is it fast ? it has a lighting bolt donut? B___H please, I can remove 90% of your so called "beauty" with a kleenex

06-02-2005, 08:40 PM	#9
RainFade Registered User Join Date: Nov 2004 Location: Central Ohio Posts: 215	Look on the front of the combo valve for a rubber cap it is over the thingy you depress when bleeding IIRC __________________ 71 K20 350/350/205, dealer air, 4" lift, Flowtech,Edel 1406 on 2101, procomp HEI,4.10's, 33x12.50x16.5 BFG MT's on slots. 4 wheel disc brakes. My lame K20 page My lame Eaton disc brake page

08-09-2005, 03:00 PM	#10
K5KRAZIE Registered User Join Date: Oct 2002 Location: Wa. State Posts: 352	Now revisited, what the hell. I put a 3/4 ton booster on and blead all the air out. Getting the air out turned out to be more of a pain than I thought. I still think theres more in the system but it stops now. Very good upgrade IMO I think the dual diaphram booster should be on all of these trucks. __________________ TRUCKS '72 K5 '06 mega dually

08-09-2005, 07:51 PM	#11
71meangreenc10 Its a Truck Thing...... Join Date: Dec 2004 Location: Sierra Vista, Arizona Posts: 3,179	You have to change the master cyl to one thats for disk/disk setup if you havent already, the resvoirs are different and the diameter of the piston is different. Once you do this and bleed the air out, make sure the rear calipers are in the right position to bleed, you will notice a definate improvement. Also the prop valves are different too. Smitty __________________ 71 C10 283/3SPD Full Resto 71 GMC 1500 Sierra Grande http://67-72chevytrucks.com/vboard/s...d.php?t=518599 70 C10 Suburban Former military GSA truck. 72 Chevy Blazer 4X4, Sloppy Jo, Mountain Climber. Wife says no more trucks. http://67-72chevytrucks.com/vboard/s...d.php?t=707378 72 GMC 1 Ton Motor Home, wife said no more trucks until she saw this one. Gen 3 6.0/4L80E 4.10 http://67-72chevytrucks.com/vboard/s...d.php?t=761110 68 GMC Suburban was 3/4 ton, now 1/2.Wife shook her head 71 C30 Wrecker 71 C20 Scott-Bilt As weird as it gets..BB Cheyenne AC Truck 68 GMC Long Stepside. They keep following me home 69 C30 Former Motor Home, Flat Bed time 70 G20 Red-E-Kamp Conversion "I'm your Boogy Van" Last edited by 71meangreenc10; 08-09-2005 at 07:52 PM.

08-10-2005, 01:35 PM	#12
K5KRAZIE Registered User Join Date: Oct 2002 Location: Wa. State Posts: 352	Maybe 4wd is different my master (now 3/4 ton) is more than capable for the disks. The prop. valve has the residual valve in it for the rear drums, but the rears do not lock up before the fronts so I think I'm OK there as well. __________________ TRUCKS '72 K5 '06 mega dually



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