Brake nightmare - help please!

Wow, thanks for the help guys. I have alot of things to try here - but one thing mentioned a few times above stands out. The bleeders are at the bottom of the calipers! It makes complete sense that the air would be trapped in both calipers causing this problem. I must have them reversed. That's the first thing I'm going to try.

As to a few other items - it's a disk brake/drum brake master cylinder (small reservoir for drums and big one for disks), not a drum only.

The prop valve really should be there to make sure the rears engage before the fronts so that the car doesn't spin under heavy braking. I've had this before on a mustang that was converted to front disks and it was no fun.

I'll report back, thanks!

the prop valve only limits the pressure going to the drums you dont want them locking up before the disks catch, in all front disks you want them to start the braking before the rears kick in(in all the readings i have done in the 4x4 world this is the way it is) i.e. step on the brake pedal and the disks just start touching, then the rear drums start engaging. Same reason most cars are front wheel drive, with the front disks engaging first you have two non steering wheels in the back still rolling keeping the car inline.


if your bleaders are on the bottom than that is your problem guaranteed, you swap them so they are on the top bleed it and you will have brakes

I have a friend running rear disk swap on a samurai and he has to run with the bleeders down, so he takes the calipers off points the bleeders up still connected to the hose(not hard line) and bleeds them like that and then puts them back on.

though i wouldnt suggest doing this for front disks or a vehicle thats on road, his sammy is primarily offroad rig


here is some decent reading
Braking Systems in Plain English

Automobile Brakes - A Short Course on How They Work

Those are excellent articles. I didn't catch any inaccuracies with just a really
quick read.....

The 1st poster's issue is definitely the bleeders, if they indeed aren't pointing
up. The only other possible cause could be front brake hoses, IF they were
standard rubber OE style. (manufacturing defect, hose ID reduced somewhere
internally. You see it every once in awhile, but 2 on one vehicle
would be a bit unusual)

Proportioning valves DO NOT (as a direct function of their design) cause the
rear brakes (drum or disc) to drag first, thereby helping the vehicle stop
straight. Prop valves cause a reduction in line pressure to the rear brake
system, making it slightly less powerful or effective..... the obvious side-
benefit is that the car DOES stop straight. (yeah, I know the devil is in
the details)

Disc vs Drum master cylinders- no real difference, just the fact that many
drum masters have residual check valves in their outlet ports. These little
umbrella valves tend to allow a slight amount of pressure to remain in that
particular circuit, helping keep brake shoes closer to the drums than they
would otherwise be.......

Akebono Brake Corporation
Brake Technical Design Center
Farmington Hills. MI

Originally Posted by malodin

fe, most aftermarket prop valve's are just one line in and one out with an adjustable regulator built in. I dont think his prop vavle he is using is going to both front and rear

Got ya. Didn't read where it was an aftermarket prop valve...

Found the Bleeders on upside down huh....

We all goof up sometimes

Well, it was the upside down calipers! Thanks guys for the help, i was about to give up.

It looks like "Another mystery solved gang" Way to go Shaggy and Scooby!

Originally Posted by ironmachineus

The prop valve really should be there to make sure the rears engage before the fronts so that the car doesn't spin under heavy braking. I've had this before on a mustang that was converted to front disks and it was no fun.

The METERING VALVE holds off front disc application until the rear drums are energized (@ approximately 30#). Without this valve, the front discs are energized first and do all of the braking. On wet road surfaces, the front wheels will lock giving no steering control.

The REAR PROPORTIONING VALVE limits fluid pressure to the rear drums in an emergency/panic stop situation. If allowed to lock, the rear end will swing around, especially on a wet road surface.

Even when calipers are installed correctly (bleeder up), they may not point exactly straight up and one has to pivot the caliper to get the most effective bleed and then tie them down.

When appling air to remove caliper pistons, place a piece of wood to catch the piston before it hits the caliper housing .

Also do not place your fingers in the way of the piston.