Big Brakes

pormgb · #1 (**permalink**) 02-08-2016, 10:31 PM

I have Sierra 4 pot calipers on the front with 1.85" and 2" pistons; I am using GM metric calipers on the rear.

With this combination I am running a Ford LTD/Crown Victoria master cylinder (1" Bore). My problem is that I have no brake pressure, the pedal goes right to the floor. I have bled the brakes about twenty times an don't think there is any air in the system, I also bench bled the master cylinder. This has me totally stumped; I have built many brake systems and have never come across a problem like this.

Can this problem be related to the MC I'm using, could it be too small.

What MCs are you guys using with big brakes?

wrench87 · #2 (**permalink**) 02-09-2016, 05:35 AM

I have to ask, are all your bleeders facing up?, if not it could cause air pockets.

mdross1 · #3 (**permalink**) 02-09-2016, 05:42 AM

Wonder if the master is getting it's full travel. How are the pads sitting in relation to the rotors,they should be close to touching.

mikeinatlanta · #4 (**permalink**) 02-09-2016, 05:51 AM

1" is a big master.

1. Cap lines to rear to see if it builds pressure.
2. If not, cap lines to front and try again.
3. If not, your problem is in the master.

What you didn't say is exactly what action you took prior to the problem. Step 1 in troubleshooting. What did you do?

pormgb · #5 (**permalink**) 02-09-2016, 09:12 AM

Thanks for your reply's!!

Answers;

- All bleedr's are facing up
- I need to confirm MC travel, I'm on my second MC with the same problem.
- Pads are close to rotors
- Master is pumping fluid, I removed the rear line at the junction and a load of fluid
shot out when pumping brakes.

Regarding trouble shooting; I changes the brake lines and gravity bled the system, I also see no sigh of leaking fluid, I am also on my second MC with the same issue.

A funny thing; When I have the power bleeder attached and pumped up to about 15lb, the brake pedal does get quite hard, when the pressure from the bleeder is removes the pedal goes soft.

patrickt · #6 (**permalink**) 02-09-2016, 10:35 AM

Quote:

Originally Posted by pormgb

I have Sierra 4 pot calipers on the front with 1.85" and 2" pistons; I am using GM metric calipers on the rear.

I have Sierra 4 pot up front, and GM metric (PBR) in the rear. With this setup, I have two master cylinders -- a Tilton 74-875U for the front brakes and a Tilton 74-750U for the rear brakes.

wrench87 · #7 (**permalink**) 02-09-2016, 12:02 PM

do the sierra calipers have 2 bleeders?, one facing down and one up alot of the 4 piston calipers have 2 mayby it was overlooked.

patrickt · #8 (**permalink**) 02-09-2016, 12:11 PM

Quote:

Originally Posted by wrench87

do the sierra calipers have 2 bleeders?, one facing down and one up alot of the 4 piston calipers have 2 mayby it was overlooked.

Yes, they do. But you'd have to be blind as a bat to miss either one of them.

strictlypersonl · #9 (**permalink**) 02-09-2016, 12:31 PM

Hopefully, all the bleeders are at the top...

pormgb · #10 (**permalink**) 02-09-2016, 01:56 PM

My Sierras are GN Billet Caliper 002-0450, they have two bleeders up top and a crossover on the bottom.

pormgb · #11 (**permalink**) 02-09-2016, 01:59 PM

Quote:

Originally Posted by patrickt

I have Sierra 4 pot up front, and GM metric (PBR) in the rear. With this setup, I have two master cylinders -- a Tilton 74-875U for the front brakes and a Tilton 74-750U for the rear brakes.

I see, I was wondering if I should go to a dual MC configuration. My Sierra calipers have quite large pistons and am wondering if I would be able to balance the fronts with rears with a single MC.

razerwire · #12 (**permalink**) 02-09-2016, 03:11 PM

gravity bled? Are calipers above level of master cylinder? You have power bleeder? You have pressure gauge? You have 2 lb check valves, one for back and one for front? You have line pressure adjuster for rear brakes? You have 3/16 inch stainless lines? No one to help me. Have set of Earls spring loaded bleeders or should I use power bleeder? Doing brakes on Bennett car right now, just talking out loud to myself. FWIW

D-CEL · #13 (**permalink**) 02-09-2016, 03:20 PM

Pormgb,

I would say you have a big bubble in one or more of the lines somewhere in the system. I too chased pedal issues. I solved it by reverse bleeding from the calipers. I took the cap off of the M/C and kept emptying it. After a few rounds, a couple of big bubbles emerged and all was well.

I hope that helps

JASON

DanEC · #14 (**permalink**) 02-09-2016, 04:00 PM

Quote:

Originally Posted by razerwire

Have set of Earls spring loaded bleeders or should I use power bleeder?

I had to go to self-sealing speed bleeders on my ERA to get everything bleed firm - the rebuilt calipers on my car were typical in that the bleeder threads are usually oversize and leak air around the bleeder screws no mater if you try pressure bleeding or vacuum bleeding the system. Since you are working alone, the spring loaded bleeders are very convenient.

pormgb · #15 (**permalink**) 02-09-2016, 09:33 PM

Well, took a look at the MC and more than 1" of the pedal travel is obstructed by a steel plate that reinforcing the MC mount. I was able to cut most of the steel away and now have over 1" more travel. I will now bleed the brakes again and see what happens.

mdross1 · #16 (**permalink**) 02-10-2016, 05:23 AM

Once you get a solid pedal and the car stops the way it should your fine. Your next concern will be how well does the car stop if it takes too much peddle pressure there are solutions to that problem as well.
I went through near the same issues when setting my car up with Wilwoods.

pormgb · #17 (**permalink**) 02-13-2016, 07:16 PM

Got my wife to help me bleed the brakes and the problem still exists, I don't think there is air in the system, something else must be wrong. When I pump the brakes, the pedal does get hard but wait a minute or two and the pedal goes to the floor.

I took a look at the front calipers and there is quite allot of visible piston (3-5mm), this is with the pads against the disk. This space is due to the large calipers with 11" Granada rotors, If I add this space up on all pistons, its quite allot.

I am wondering if the pistons could be riding back and have to travel too far when the brakes are applied.

patrickt · #18 (**permalink**) 02-13-2016, 07:42 PM

Quote:

Originally Posted by pormgb

I took a look at the front calipers and there is quite allot of visible piston (3-5mm), this is with the pads against the disk. This space is due to the large calipers with 11" Granada rotors, If I add this space up on all pistons, its quite allot.

What is the thickness of the Granada rotors? The rotors I'm running with my Sierras are part #003-1162 and are 1.25". Old page on them is here: Sierra Racing Products - Vented Rotors

patrickt · #19 (**permalink**) 02-13-2016, 07:59 PM

If your Granada rotors are these: 11" Granada 5 Bolt Rotors,Available in Ford or Chevy Bolt Pattern then they are just 1" thick, at best, and could be 7/8".

pormgb · #20 (**permalink**) 02-13-2016, 08:24 PM

Quote:

Originally Posted by patrickt

If your Granada rotors are these: 11" Granada 5 Bolt Rotors,Available in Ford or Chevy Bolt Pattern then they are just 1" thick, at best, and could be 7/8".

Yep, they are 1".

Pumping the pedal builds good pressure, I can't imagine where air could still be in the system.