Brake Question

[brew8]

I put a brake booster and MC from a 76 chevy truck on my 62 chevy 4x4, we bleed the system and it stilkl goes very far down to be firm. I built the rod from the brake pedal to the booster so it had no or just a little space till it hit the push point, it will not pum up more so I think I am either ok with the adjustment or hitting the end of the MC bore. so I have a few questions. Do I need to have more distance on the rod to partially compress the MC to take uup the slack? Do I need to move the small push pin out in the front of the MC and are they adjustable? Did I just not bleed out the MC as well as I shoulkd have. I did build the two circuits front and rear, I have disc brakes in the front and drums in the rear, let me know what you think Larry

BTW I through in a pic, Larry

[OrrieG]

I would first try and bleed it out better. When you have had a system completely a part it can be a bear to get all the air out. Make sure the front calipers have the bleeder up so it won't trap air, not down the caliper will fit both ways. Self bleeders will help too. Make sure all the fittings are tight and not sucking air.

Assuming you kept the pedal pivot geometry the same as stock and the push rod is snug against the booster diaphram and the booster to cylinder rod is tight the distance the master cylinder move should be right. If the rod on the pedal is closer to the pivot point it will not move the master cylinder as far, if its farther away the mc will bottom out before the pedal get close to the floor. If the pedal geometry is ok then its back to a bleeding or mc or proportioning valve problem.

If the mc sat for some time, even new, the seals may not work right. I put in a brand new master cylinder 3 years ago.,bleed everything out and had it working fine. Late last summer I noticed a puddle of fluid and ended up replacing the mc because I had not been exercising the seals.

Other things to look for are to make sure you do not have any places in the lines that can trap air. I turned the circular spiral line out of the mc sideways to make it fit better sideways and could not get it to bleed right, air was getting trapped in the top of the loops. I rotated it back vertically and all was well.

I hope this helps, getting these right can be a lot of work.

['63GENIII]

Are you still running drums all the way around? If so, you may need a residual pressure valve(s). I did the same thing to my '63 only to realize that the drum brake require a small amount of pressure to keep the wheel cylinders from retracting all the way, which turns into lots of pedal travel before the brakes actually start working....and they never worked well. If I recall correctly, they were @ 15 bucks a piece from Jegs or Summit I think. I put them in after the proportioning valve and used them until I swapped in the front disc setup. At that point, I took out the front valve. It may sound crazy but I was told that all drum brake systems have them somewhere in the system. I had the same problem for months until I a post somewhere else about it. I've had great brakes for a couple years now.

[brew8]

I put a dana 44 disc brake axle on the front so I have disc brakes there now, I am going to try the bleed again and see how that goes, when I had the drums all around I gravity bled them and it worked great, I may need to look at some high spots but I'm thinking it's the master cylinder tht is not bled correctly, thanks, Larry

[Mr-Jack]

Did you bench bleed the master cylinder before installing it? that could be something to look at

[brew8]

Well I rebled everything, I did the master in the truck I read a way that said jack up the rear of the truck to level the MC and bleed it there, worked good, bought a vacuum bleeder from Harbor freight worked great on the wheels, have a great pedal now, thanks for the advice and help, Larry

[Mr-Jack]

i've never really liked the hand bump zerk bleeders they are alright, but i'd rather not use them power bleeders are better. glad you got a good pedal now tho. never heard of jackin the rear of the truck up to bleed the MC. i've always just bench bled them prior to install and never had a problem

[brew8]

I should have bled it first but it was in the truck and some guy I googled said you could jack the rear of the truck to level the MC, so I gave it a go, Larry