Please can someone help me im completely lost

[Turbizzy]

Yes im sorry its another great disc brake question and beleive me i tried super hard to search but so far its just made me even more confused and my dad really needs his truck back asap.

OK, my dad bought this 68 c10 with disc brakes up front and 5 lug rotors. I swapped the rotors for 6 lug rotors from Early Classic along with new bushings, balljoints etc. However the truck never really seemed to stop well. The master cylinder was an aluminm style with the plastic clip on top resevoir. And it had no Proportioning Valve only that early block style looking one.

When you step on the brakes the pedal goes to the floor practically and does stop decent when unloaded but its really dangerous. I tried to bleed the brakes but i don't get a whole lot of pressure out of the calipers so i thought perhaps the master cylinder is bad/wrong.

So far i swapped in a rebuilt master cylinder from a 72 c10 with discs from AutoZone and a new prop valve from early classic. Connected it all and when i tried to bleed it i noticed the fluid bleeds off better at the calipers however the pedal still hits the floor and i feel like the brakes didn't get much better.

Im soo frustrated right now since no one can really give me an answer since who knows what the previous owner used parts from. Anyway what i think is going on is that the master cylinder isn't building enough pressure due to not enough travel from the booster. I bought a rebuilt booster from Autozone and compared the 2 and sure enough the old booster only pushes the pushrod into the master cylinder about 50% of what the new booster does. Well when i tried to install the new booster i realized the new booster doesn't have those mounting brackets to the firewall. The firewall has 4 studs that stick out, 2 short on top, 2 long on bottom. And those studs go into the old booster's mounting brackets which by the way are riveted to the booster. So i thought about griding off the rivets from the old brackets and installing the new booster onto the old brackets but.... theres another issue. The rod that goes from the pedal to the new booster is really short and has a small loop hole at the end. This will not reach the pedal at all. The old booster has a really long rod that seems to be threaded with a jam nut and is the perfect length from the brake pedal to the booster.

Needless to say i don't know what to do anymore and its really tough trying to describe this to anyone. So i think what i basically want to know is... what kinda booster do i need, i plan on buying a rebuilt one from Autozone or a junkyard iunno. And how do i make it bolt to the pedal since the one i bought has a input rod that is too short?

Can you guys post some pics of your brake booster/MC installs? Thank you soo much for your time i really appreciate it.

[Bishops Trucks]

Did you bench bleed the new mastercylinder before you put it on?

[sneakysnake]

Throw in a few pics, it helps to see what were dealing with.

[hgs_notes]

Might be a dumb question, but is there good vacuum to the booster? You really won't get "good" pressure to the calipers during bleeding. But wuth the truck running and good vacuum to the booster, the pedal travel is not really very far. The rod from the pedal to the booster may have been swapped with the one for the master cylinder you replaced, in which case, it might not work with the "correct year 1972" booster/master cylinder. If it was mine, I would check for good vacuum to the booster, then if that was ok, I would run to the junkyard, find a 67-72 truck with power brakes and get the rod from the pedal to booster and compare them. If it is different from what you have, that may be the problem. Another thing, sometimes the flexible brake lines to the calipers weaken and will flex with applied brake pressure, reducing the amount of fluid pressure to the calipers. All it takes is one week line and the front brakes are spongy. If not, keep bleeding the brakes.

BTW, I never bench bled my new master cylinder when I made the swap, and had no problems. I had also replaced all the lines for the front brakes at the time.

[Turbizzy]

I bench bled the new master on while installed on the truck, i used those 2 little hoses and submerged them into the resevoir brake fluid so i know im good there. And yes i also replaced those brake hoses to the calipers when i did the bushings cuz those were cracked as well.

As far as the vacuum i have not tried turning the truck on at all. I figured it shouldn't have anything to do with vacuum since the pedal pretty much hits the floor if i force it slightly. Ill try to take pics of my setup but unfortunately i already returned the new booster since i didn't think it would fit.

[68gmsee]

If you are sure the master cylinder and brakes have been bled properly, and there is not excessive play on the brake pedal push rod, then more than likely you have a bad master cylinder.

The vacuum booster only assists you. It shouldn't cause the brake pedal to go down to the floor.

[Richard H.]

From what I read it sounds like the mounting bracket is wrong. The bracket on my 71 bolts to the firewall and the booster "bolts to the bracket". no rivets. I will try to find the bracket and get you a picture of it.
You can damage the MC by pushing the pistons in to far!

[krue]

You have the booster off of a 73-87, you need the brackets to mount the original style booster. You also probably need the connection between the pedal and the booster. Check the parts board, they are on there frequently. You're not gonna get it to work with mismatched parts.

[Turbizzy]

My booster basically looks like this including the mounting bracket attatched to the back of it that bolts to the firewall.



This is what looks like is on there now only hella old and rusty. Althogh i think the booster thats on there isn't as thick as the one pictured above.

It just seems that the pedal is too long and hits the floor pan before any real pressure is made inside the MC.

Also i tried searching for a new booster and none come with the threaded input rod like the one in the picture i posted. All of them have a shorter input rid that isn't threaded and has a loop for a pin at the end like this one:



Plus it doesn't have the mounting bracket like the one above. I would order the one above (gold) but its 250 from early classic and i wanna get something cheaper if possible.

What i think i need is more pedal travel.

[chevy_mike]

My .02 worth. Back when I had my '68, I was swapping '72 discs onto it. I pull a booster off another truck at the junk yard, bought a new '72 MC and everything bolted up. Never really had a good pedal and it took too much effort to put. After screwing around with this for a while, I ended up buying a booster/MC from Master Power Brakes for this app. It solved all the problems.

It might be more expensive to just buy a whole unit from ECE or Master Power but odds are it will work correctly the first time. Hodge Podging things together doesn't always work out so well.

YMMV. Good luck.

[Turbizzy]

Hmm right on Chevy Mike i appreciate the input as well as everyone else. But really im not trying to rig anything im trying to put all stock stock on there. The MC i bought from Autozone is for a 72 with disc brakes. The Prop valve i bought from Early Classic also is for a 72 style disc brakes. I even got the lines from the MC to the prop valve from Early Classic. At this point im kinda outta ideas. Could it be that maybe the lines from the brakes to the prop valve are 1/4" lines and the lines from the MC to the prop valve are thinner 3/16"?

[Turbizzy]

OK guys i just got off the phone with Early Classic Enterprises (ECE?)'s awesome tech support and i spoke to Terry. He basically told me what my problem is that i do in fact have the wrong booster setup on there. He said the booster that is on there is for a later 73-87 style truck and if i had an aluminum master on there before then for sure thats it. He says that booster has a shorter throw (basically less movement internally) and therefore doesn't push the master cylinder in far enough for it to build any decent pressure.

Those guys rock, they weren't even trynna sell me their booster at all, he told me to go to a junk yard and find a booster and bracket setup and to make it work however i just don't have the time and patience anymore to do so. So then he suggested i go back and buy the booster from Autozone for $100 then he'll sell me a booster mounting bracket for another $100 and to go and get the CANTILEVER linkeage setup from a older truck since mine is missing. I told him again that i don't wanna go JY route anymore so lastly he suggested his booster would work perfectly and has the threaded input rod like the later style and bracket to mount it to the firewall and is gauranteed to fit.

So i ordered the booster, should be here tomorrow. He said he was out of the 9 inch ones that they usually sell alot of but that he had some 7 inch ones. I asked what the big differences were and just said the 9 inch would have more power but its not a big deal if i have a stock truck with stock wheels and brakes which i do so yea....

ANYWAYS thanks guys. Ill let ya know how it comes out.

[chevy_mike]

Yep, sounds like the new/JY method was what I was trying and it just had too many problems. Glad you just went the right setup from ECE. You should be happy with brakes that work right.

[krue]

If you had posted a wtb on the parts board you would have got a stock setup WAAYY cheaper than that, but if it works it works.