Braking - The 1947 - Present Chevrolet & GMC Truck Message Board Network

wHATANERD · 12-10-2003, 09:23 AM

About a year ago I converted my 69 C/10 over to 71/72 disc brakes by replacing the front crossmember, however the brakes have never felt right since. The booster is the one the was working fine when the truck was drum/drum, and do not feel that it is the trouble. I have a new 71 / 72 proportioning valve, a new master cylinder, but still have excessive play in the petal. The first master clyinder was a Raybestos 2 bail, this caused the brakes to stop slower than desired( not sure if it was going to stop or not ), and unable to lock up under extreme braking. I also tried a Bendix Master Cylinder, this one works better, but made the brakes extremely touchy ( brake petal would travel about 2 inches with out stoping, and would instantly lock up). If anyone has had the same trouble, pr any sugestions, it would be greatly appericiated.

Mark540 · 12-10-2003, 09:58 AM

Sounds to me like the brakes need to be bled, even if you have done this already, get a one man kit and completely flush and bleed the system. I would rule this out before buying more parts.

**Palf70Step** · 12-10-2003, 10:26 AM

Like Mark540 said sounds like air in the system. It took me what semed like 80,000 tries when I had to replace lines and a proportioning valve to getmine right.

Another thing since you have a mixture of parts, you might need to readjust the pedal rod that goes between the booster and brake pedal to get the feel you desire.

wHATANERD · 12-10-2003, 12:34 PM

Thanks for the input, I will be working on it again this weekend, I have ajusted the petal rod, and the brakes have been bled numerous times, but will try again, when I find my digital camera I will be submitting some photos, as I have some questions about the type power booster types ( Delco, Moraine, Bendix) .The braking system should be identical to whats on a 71 or 72 truck. My truck already had power drums, and believe that the booster is the same for both drum, and disc ( Please correct me if I'm wrong). The only thing I can thank of is the rod between the master cylinder and the booster may need adjusting. Any sugestions are appericiated.

krue · 12-10-2003, 04:40 PM

Quote:

The only thing I can thank of is the rod between the master cylinder and the booster may need adjusting. Any sugestions are appericiated.

That is what I would suggest trying. May take a little trial and error to get it right.

wHATANERD · 12-15-2003, 06:24 AM

Great news the brakes are fixed, a combination of replacing the master cylinder and adjusting the rod between it and the booster fixed the trouble.

**Palf70Step** · 12-15-2003, 07:46 AM

Glad to hear it. It is always nice to know that the brakes work...Who knows you might actually need them someday!

12-10-2003, 09:23 AM	#1
wHATANERD Registered User Join Date: Mar 2003 Location: Uvalde, Tx Posts: 407	Braking About a year ago I converted my 69 C/10 over to 71/72 disc brakes by replacing the front crossmember, however the brakes have never felt right since. The booster is the one the was working fine when the truck was drum/drum, and do not feel that it is the trouble. I have a new 71 / 72 proportioning valve, a new master cylinder, but still have excessive play in the petal. The first master clyinder was a Raybestos 2 bail, this caused the brakes to stop slower than desired( not sure if it was going to stop or not ), and unable to lock up under extreme braking. I also tried a Bendix Master Cylinder, this one works better, but made the brakes extremely touchy ( brake petal would travel about 2 inches with out stoping, and would instantly lock up). If anyone has had the same trouble, pr any sugestions, it would be greatly appericiated. __________________ 1969 C/10 Longbed undergoing rebuild. Old Chevy's Never Die, They Just Rust Around The Edges

12-10-2003, 09:58 AM	#2
Mark540 Registered User Join Date: Feb 2003 Location: Fairborn,OH Posts: 203	Sounds to me like the brakes need to be bled, even if you have done this already, get a one man kit and completely flush and bleed the system. I would rule this out before buying more parts. __________________ 1970 GMC Burb 4x4 - 68 Chevy Front, FI LT1, 4L60E 1970 Chevy Impala 47,000 miles 2001 BMW 540i 6-speed 2002 Dodge Ram 1500 4x4 w/20's

12-10-2003, 10:26 AM	#3
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 46,820	Like Mark540 said sounds like air in the system. It took me what semed like 80,000 tries when I had to replace lines and a proportioning valve to getmine right. Another thing since you have a mixture of parts, you might need to readjust the pedal rod that goes between the booster and brake pedal to get the feel you desire. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God!

12-10-2003, 12:34 PM	#4
wHATANERD Registered User Join Date: Mar 2003 Location: Uvalde, Tx Posts: 407	Thanks for the input, I will be working on it again this weekend, I have ajusted the petal rod, and the brakes have been bled numerous times, but will try again, when I find my digital camera I will be submitting some photos, as I have some questions about the type power booster types ( Delco, Moraine, Bendix) .The braking system should be identical to whats on a 71 or 72 truck. My truck already had power drums, and believe that the booster is the same for both drum, and disc ( Please correct me if I'm wrong). The only thing I can thank of is the rod between the master cylinder and the booster may need adjusting. Any sugestions are appericiated. __________________ 1969 C/10 Longbed undergoing rebuild. Old Chevy's Never Die, They Just Rust Around The Edges

12-15-2003, 06:24 AM	#6
wHATANERD Registered User Join Date: Mar 2003 Location: Uvalde, Tx Posts: 407	Fixed Great news the brakes are fixed, a combination of replacing the master cylinder and adjusting the rod between it and the booster fixed the trouble. __________________ 1969 C/10 Longbed undergoing rebuild. Old Chevy's Never Die, They Just Rust Around The Edges

12-15-2003, 07:46 AM	#7
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 46,820	Glad to hear it. It is always nice to know that the brakes work...Who knows you might actually need them someday! __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God!



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