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

*MJF* · 10-29-2003, 06:41 PM

I need some help. I swapped a disc brake axle in place of the drum axle in my wife's truck. To complete the swap, I put a new master cylinder, new calipers up front & new brake lines to the calipers. I bled the system & checked for any leaks. No leaks so I took it for a test drive.

When I push the brake pedal down, it only returns half way. The brakes work except for the pedal sticking. When it gets stuck half way down, the brakes are being applied with the force of half pedal & the pedal never returns fully up, even if you drive that way for 50 feet or so.

What in the brake system would cause the pedal to not release the pressure to the brakes? I was thinking master cylinder, but wanted opinions.

I should probably add that I don't have a proportioning valve yet. It's on the list for the next thing I will buy, but just can't get it yet. I jsut needed to be able to move the truck so I can empty the junk out of the back. I do have power brakes & got a m/c for a 71 with pwr brakes & discs up front.

sactoC10 · 10-29-2003, 06:48 PM

When I was having this problem recently, it was the rubber boot inside the booster. It was torn and fallig apart, thus when I'd press the pedal, the brakes would engage, but this rubber boot would HOLD the pin type piece that enters the booster. If the truck would sit for a while, then the pressure would eventually push it back out and I could use the brakes again (once or twice) upon starting it up the next time.

Sucks. Spent much $$$ figuring that out.

If you don't have a power booster, then I do not know. Just letting you know what caused mine to stick. 1971 LWB

*MJF* · 10-29-2003, 07:22 PM

That sounds like it might be my problem. I made a bonehead mistake & "broke" the rod that goes from the brake pedal to the booster. I was making adjustments to the length by screwing it in & out. I got it a little too far out & stepped on the brakes & popped it off of there, stripping the threads on the threaded rod.

I don't have atap & die set so I cleaned the threads as best I could & just went ahead & wrenched it on there. It now sits crooked & it's propably rubbing on the piece you described inside the booster from being in there at a funny angle.

*MJF* · 10-29-2003, 08:08 PM

Well after thinking about it for a few more minutes, the rod I'm thinking about doesn't go into the booster. It is the one that runs from the pedal through the firewall to the booster. But your description does give me a few other things to check out.

Alexis · 10-29-2003, 08:14 PM

did you brake in the MC on a bench?

*MJF* · 10-29-2003, 08:47 PM

Well I "fixed" it. Since that rod that runs from the pedal to the booster was cross threaded, it was crooked & hitting the firewall where it goes through to the booster. I jacked with it & made it crooked the other way so it wouldn't rub.

Now I need to find new pieces for this so I can fix it the tright way. Somehow the thought of this rod popping off the brake pedal as I'm driving down the freeway doesn't sound so appealing to me. This truck doesn't get driven much right now so it's fine for just moving it around in the driveway.

Does anyone actually know what I'm talking about & know where I can get the threaded rod & whatever the other piece that attaches to the pedal is called from? If I ordered a whole new booster would it come with the pieces that go throught the firewall to the brake pedal?

10-29-2003, 06:41 PM	#1
MJF No longer truckless Join Date: Mar 2002 Location: Campbell, CA Posts: 299	frustrating brake swap I need some help. I swapped a disc brake axle in place of the drum axle in my wife's truck. To complete the swap, I put a new master cylinder, new calipers up front & new brake lines to the calipers. I bled the system & checked for any leaks. No leaks so I took it for a test drive. When I push the brake pedal down, it only returns half way. The brakes work except for the pedal sticking. When it gets stuck half way down, the brakes are being applied with the force of half pedal & the pedal never returns fully up, even if you drive that way for 50 feet or so. What in the brake system would cause the pedal to not release the pressure to the brakes? I was thinking master cylinder, but wanted opinions. I should probably add that I don't have a proportioning valve yet. It's on the list for the next thing I will buy, but just can't get it yet. I jsut needed to be able to move the truck so I can empty the junk out of the back. I do have power brakes & got a m/c for a 71 with pwr brakes & discs up front.

10-29-2003, 06:48 PM	#2
sactoC10 71 DELUX Join Date: Sep 2003 Location: Northern CA / Sac Posts: 1,056	When I was having this problem recently, it was the rubber boot inside the booster. It was torn and fallig apart, thus when I'd press the pedal, the brakes would engage, but this rubber boot would HOLD the pin type piece that enters the booster. If the truck would sit for a while, then the pressure would eventually push it back out and I could use the brakes again (once or twice) upon starting it up the next time. Sucks. Spent much $$$ figuring that out. If you don't have a power booster, then I do not know. Just letting you know what caused mine to stick. 1971 LWB

10-29-2003, 07:22 PM	#3
MJF No longer truckless Join Date: Mar 2002 Location: Campbell, CA Posts: 299	That sounds like it might be my problem. I made a bonehead mistake & "broke" the rod that goes from the brake pedal to the booster. I was making adjustments to the length by screwing it in & out. I got it a little too far out & stepped on the brakes & popped it off of there, stripping the threads on the threaded rod. I don't have atap & die set so I cleaned the threads as best I could & just went ahead & wrenched it on there. It now sits crooked & it's propably rubbing on the piece you described inside the booster from being in there at a funny angle.

10-29-2003, 08:08 PM	#4
MJF No longer truckless Join Date: Mar 2002 Location: Campbell, CA Posts: 299	Well after thinking about it for a few more minutes, the rod I'm thinking about doesn't go into the booster. It is the one that runs from the pedal through the firewall to the booster. But your description does give me a few other things to check out.

10-29-2003, 08:14 PM	#5
Alexis Member since 2000 Join Date: Dec 2000 Location: Mountain View Ca / Mexico Posts: 7,879	did you brake in the MC on a bench?

10-29-2003, 08:47 PM	#6
MJF No longer truckless Join Date: Mar 2002 Location: Campbell, CA Posts: 299	Well I "fixed" it. Since that rod that runs from the pedal to the booster was cross threaded, it was crooked & hitting the firewall where it goes through to the booster. I jacked with it & made it crooked the other way so it wouldn't rub. Now I need to find new pieces for this so I can fix it the tright way. Somehow the thought of this rod popping off the brake pedal as I'm driving down the freeway doesn't sound so appealing to me. This truck doesn't get driven much right now so it's fine for just moving it around in the driveway. Does anyone actually know what I'm talking about & know where I can get the threaded rod & whatever the other piece that attaches to the pedal is called from? If I ordered a whole new booster would it come with the pieces that go throught the firewall to the brake pedal?



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.