The Stovebolt Site Forums The Shop Area The HiPo Shop Binders are lockin' up! Help my hard pedal

I have a problem with brakes locking up after engine warms,if I crack a line open at the master it will relieve some pressure so i can roll again, but afew miles down the road it happens again. My setup is a relatively new one Master cylinder,prop valve,etc bought from ChevyDuty, on '79 nova front clip, and rearend same doner, front disk and rear drums, '52 1/2 ton, '61 235 intake is where the booster gets it vacuum. Ive looked at many posts but havent found much to address hard pedal problems, could someone please help or steer me the right direction. Oh, and sorry for the long "first" post, but if anyone knows the answer its a "Bolter"! LoL Thanks Rob

When that happened on mine it was due to "heat" from the exhaust pipe running next to the master cylinder and brake line, another possibility is "old" brake fluid has collected moisture, "water" expands more than brake fluid when it gets hot.

Ah, yes I do have an exhaust pipe running about 7 inches away from the outer diameter of the booster housing,Ill run some aluminum 1/16 in. plate stock around the pipe tommorow and run her around the block till shes nice and warm, ive tried just about everything else short of rerunning all the lines etc. That makes good sense, thanks abunch Yakimabowtie, Ill post again tomorrow

When you assemblied the system did you adjust the rod between the boster and master cylinder? There has to be a little clearance between the two or the brakes will drag and get even worst as they heat up.

Beltfed has it, add some clearance at the pedal to master rod. May have to back off the shoes a few clicks too,
Scott

Agree with Beltfed, We had the same problem with my sons 68. Backed the rod off a little and the problem went away. We figured it out by taking the brake drum most of the way off so you could see the brake shoes move. pumped the brakes a few time and you could see the brakes took forever to release.

Well it looks like I adjusted the rod "out" too far towards the front of the truck, about 1/2 from pedal assembly and 2 1/2 from booster. DUH, so if I understand u guys correctly it needs to be adjusted back the "other" way towards the booster with a minimal clearance? Ill run new fluid and back the rear shoes off a bit too just to eliminate possibilties. Thanks EVERYONE!!

Not the pedal adjust, the adjust between the master and the booster. Pop the master free of the booster (if you installed the lines with enough play, no need to remove lines) and you should see and adjuster rod on the booster.

FYI, The spacing between the booster rod and the 'cup' in the master cylinder piston is 0.020". There is a handy inexpensive little tool for setting this spacing. It looks like a "H" with a rod running through the "H". Might be able to borrow one from your FLAPS. Good luck

Just a few lines to say MANY THANKS, beltfed, Chuck the truck,CenTex52 Chevy,48 bigtrucks, Yakimabowtie, you guys RULE!!! Got the binders goin again and spent most of Sunday crusin!! Thanks for the help!

Are ya gonna share the fix with us ??

Absolutely!! Well, the problem was I had A hard brake pedal after the engine was nice and warm eventually locking up the brakes. The master/booster assembly was purchased from (CCP) not ChevyDuty as I originally posted. The assembly is an aftermarket set up since I have the nova clip/rearend etc, and "should" mount in the "stock location", under the floor, an important point I need to make. The actual fix went like this. After eliminating all the heat sources, exhaust heat, engine heat, etc. Rebent and flaired a couple of lines, bled the system with new fluid. We've moved a couple of times so the truck hasn't been driven very much since I installed that assembly so new fluid and so forth made sense. "Now" adjusting the rods, I found when I cracked the master cylinder and booster apart that the push rod inside was adjusted in towards the booster as far as it would go and would still make contact with the master cylinder diaphragm. Just out of "curiosity" I removed the push rod and closed the assembly back up. Started the truck and let it warm. Even before the engine warmed, I still had too much drag on the wheels. So cracked the assembly and master booster back open and adjusted the pedal assembly rod and everything so that everything would be as loose as it could be even the pedal assembly rod. It still had too much drag. "OMG". Where in the hell did I put the instructions? As I was looking for the instructions that I was pretty sure that I had lost, the thought came to me that I may have mounted the whole assembly about an 1/8 to 1/4 of an inch too far foward. Panic set in as I begin to think about tearing this whole assembly and moving the transmission cross member out of the way etc. I thought " I'll just put some space between the master cylinder and the booster" The proportioning valve sits on a bracket mounted underneath the master. The bracket itself is about an 1/8 of an inch wide with the vertical flange on the outside "Kinda hard to explain without pics", but I just moved that bracket between the booster and the master and it gave me an 1/8 of an inch or more of clearance with the push rod in installed all the way down. Backed off the rear shoes a couple of clicks, warmed up the truck and whalaa!! I have good pedal about a 1/4 of the way down and the puppy stops on a dime now. Took it out Sunday for a nice ride and everything worked great, right where it was adjusted at. So once again, a big thanks to everyone that helped me out and I hope I didn't confuse anyone with my extra long rambling!!!

Glad to hear you got the problem solved.