Thread: Disk brake help!

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Hey guys!
I need some help with a disk brake conversion I just did on my 66' Chevelle.
The brake system I bought was a SSBC(stainless steel brake corp.) system from Jegs.
My problem is I have to pump up the brakes to get a firm pedal. I have bleed the system numerous times, and every time I get straight fluid coming out of the lines (no air). I have taken this thing to a shop as a last resort so they could pressurize the system and they couldn't get them any better by doing that, and they didn't seem interested in doing any furthur investigating for me into what the problem might be.
I have checked to make sure the rear pads were already lightly touching the drum, so I don't believe I'm having to pump up the rear shoes.
The way I have everything rounted is like this:
Coming off the master cylinder it goes to a splitter valve and off of the splitter valve it goes into a proportioning valve and a line lock. Coming off the line lock it goes to a splitter that divides for the front brakes, and coming off the proportioning valve it connets to the brake line that feeds the rear drums.
I hope this is not too long, but I wanted to try to cover it all.
Can anyone tell me what I'm missing here?

Thanks
James

Richard,

Thanks for the reply.
This is a first for me, so I'm sure it's something I've done.
It is a dual master cylinder with the front feeding directly into the residual pressure valve (the one that is non-adjustable and splits the front pressure from the back) and back out of it into the line lock which goes down to a splitter to the left and right front.
The back of the master cylinder also feeds into the residual pressure valve then back out into the adjustable proportioning valve and then a line comes out of it that feeds the back brakes.
This is the 'schematic' that I downloaded from a website. It looked like it made sense...
Shouldn't the front of the master cylinder be feeding the line lock?

I will email the guys a SSBC and see if they can fax me how it should be hooked up.

Thanks again for the help,
James

Did you bench bleed your master cylinder prior to install?
Failure to do that, all the bleeding in the world won't make the pedal firm....

If you have bench bled it- you might consider running out to a parts store and getting another front Disk/rear drum master cylinder- I went through 3 the last time i had one go out before i got one that worked properly... And i have heard similar stories from other folks who have done disk swaps... Could just be a faulty master cyl.

Richard,

Thanks for the writeback. I will certainly follow what you have laid out, and hopefully that will do the trick.

Thanks again


Ben,

Yes, I did bench bleed the master cylinder. But for good measure I'm going to redo the plumbing and I will get a new master cylinder to go along.

Thanks.
James

I'll let you know when everything is done (by this weekend).

This may sound stupid but I have seen it before. Are your calipers on the correct sides? If they are not the bleeders are on the bottom and you can bleed them until hell freezes over and they wil still have air in them.

Originally posted by IBUILDM
This may sound stupid but I have seen it before. Are your calipers on the correct sides? If they are not the bleeders are on the bottom and you can bleed them until hell freezes over and they wil still have air in them.

Thanks for the help. The calipers are on correctly.
According to tech at SSBC, I've got everthing hooked up correctly.

So, I'm going to change out the master cylinder tomorrow, and see what happens.

I'll let you know what happens.

James

Well, I changed the master cylinder over the weekend, and it fixed the problem.
I would have never guessed...

Thanks for all the help.

James

hi
I was reading your post and it reminded me of a problem I ran into on a 55 chevy I was doing for a customer...I see now that your problem was the master cyllander
however alot of people forget to preload the booster....meaning when you set up your booster the rod off the pedal should depress the booster 1/8th to 1/4 of an inch with every thing tightened down...this is called preloading and it allows for a firm pedal
maybe that will help you in the future.