New disc brake system not working

[ninhalo5]

Re: New disc brake system not working

Great, thanks Bruce. I purchased the tie down brake hose kit and it came with all rubber hoses. The front one is 20' long and from the actuator to the axle is in between 15-18', so with the frames curve I would follow to get to the axle, that length should be perfect, and I'll only have to coil around the one axle line.

 

[bruceb58]

Re: New disc brake system not working

be careful about coiling lines especially on an axle. You hit some road debris and its going to get yanked off.

And always run lines when possible on the back side of the axle for the same reason.

 

[UncleWillie]

Re: New disc brake system not working

When I cracked open the bleeder, nothing at all happened, 0 dribble, rotors still locked up, until I pried the brake away from the rotor with the bleeder opened, only then did fluid come out and the brakes released enough for me to push the trailer back to its parking spot...

If the rotors are locked with the bleeders open;
There is nothing wrong with the actuator or the brake lines!

All the problems are in the Caliper Assembly.
A tiny speck of debris can cause the piston to bind.
Disassemble the caliper and get everything surgically clean.
A light polishing with Scotch Brite may help.

The Disk Caliper is higher pressure than the Drum calipers.
If you have a mislabeled one the complaint would be Weak Brakes, Not Locked Brakes.

 

[UncleWillie]

Re: New disc brake system not working

... I was investigating the brass nipple that comes out of the actuator which the hose screws into and noticed that the hole in it is super tiny, so small in fact I may be able to get a guitars E string in it but not a sewing needle, however on the other hand I glanced at the hoses and the holes on the connectors are about the size of a cross stitching needle, maybe 1/32" diameter.
With the actuators hole so small I would believe the fluid would have some major issues with back flow and releasing pressure...

The pressure in the brake lines is in the thousands of PSI range.
Even a tiny pin hole will pass plenty of fluid very quickly.
Consider the size of a pressure washer nozzle and how many gallons of water per minute go through one.
Notice that when you pumped the brakes to bleed them, only a small portion of an ounce was pumped.

If you could bleed the brakes and get fluid out the bleeder; The actuator is working.

Again, if the rotors are locked with the Bleeders Open;
You problem is in the Caliper Assembly!

 

[bruceb58]

Re: New disc brake system not working

I agree with Uncle Willie. By opening the bleeder, you removed the pressure that the master cylinder would be supplying.

 

[ninhalo5]

Re: New disc brake system not working

I seriously doubt it's entirly a caliper issue though, ( bad or dirty). in my experience with cars if the caliper is locked up or dirty you need to just about take it apart to clean it and get it compressed, sometimes even cranking it down with a C clamp is difficult. With these new calipers it hardly took any effort at all to manually part the pad from the rotor, with just a small screwdriver. That's not to say my lack of grease on the pins might have something to do with it.

I found on champion trailers web site that for disc brakes the brass fitting/ nipple must have a minimum opening of .065" or 1/8. My fitting was around 1/64" way to small, so naturally when pressing on the MC's plunger would force the fluid into the lines but the caliper cannot give enough force to send the fluid back into the MC.

Drum brakes uses wheel cylinders to adjust the pressure where disc uses just the MC and in cars a brake booster which the trailer don't have.

There's really not much that a caliper can do in the way of force by itself. I'll try to bleed the brakes again over the weekend and see how it goes with the new fitting.

 

[bruceb58]

Re: New disc brake system not working

it doesn't explain why your calipers were still stuck after you opened the bleeder screw. You did open it right?

Drum brakes uses wheel cylinders to adjust the pressure where disc uses just the MC and in cars a brake booster which the trailer don't have.

Wheel cylinders are just slave cylinders so they aren't adjusting any pressure. Brake boosters in cars just help you push on the master cylinder with less effort. Its not even relevant in this conversation.

 

[glenn property of pam]

Re: New disc brake system not working

trash in lines gets pushed under pressure to the piston then it doesnt have the pressure to be pushed back into the pipe so it acts as a blockage. You strip it down to find the problem and oil goes every where (junk with it) you put it back together wiping off as you go. Then after you refill the system it works perfect so the problem must have been..........

 

[bruceb58]

Re: New disc brake system not working

Not sure if you did this but whenever you put new lines in, you don't attach them to the brakes until you flush them out. You didn't do anything like use teflon tape or sealer on any of the brake fittings right?

 

[ninhalo5]

Re: New disc brake system not working

You guys are probably right, I just don't understand how I have tremendous pressure at the actuator and what fluid is in the caliper only comes out when applying pressure to the pads. It just don't seem like a clog or anything. I'll go ahead and take them apart just to make sure, and hit everything with the air compressor.

Heck no fluid even dripped out of the MC when I disconnected the hose from it.

 

[UncleWillie]

Re: New disc brake system not working

I just re-read your opening post.
You changed from Drum to Disk brakes.

Understand that disk brakes are significantly different in their operation.
When releasing Drum brakes, the springs will retract he brake pads.
Disk brakes do not have and retract mechanism.

When the brake line pressure is released; the Disk Pads will not retract away from the disks.
Do not expect to see any fluid come out of the bleeder unless you manually retract the brake pads. This is normal.
On Disk brakes, with the pressure released the wheel WILL be able to turn by hand.
The brake pads will still be lightly rubbing the Disk.
With New Pads, you may feel significant drag at a few spots in the rotation, and hear them rubbing. This is normal.

With pressure released, they may not be 100% free wheeling, but they will turn by hand.

 

[glenn property of pam]

Re: New disc brake system not working

just a side note: make sure you bleed both sides before testing as you can get a airlock that will give a odd felling. Always pull the hitch forwards as far as it will go before checking to see if the brakes are released (some are alittle tight and sticky) if the master is even slightly in then then oil is blocked from being returned.

 

[ninhalo5]

Re: New disc brake system not working

Well, I completely dissected the brake system, took all th ln back off, hit them with air and had a really good flow. So no clogs there, that's good. Then I took apart the calipers checked the pistons, the walls, and any fluid ports then put them back together. Now I'm in the process of reinstalling everything, I broke my drill bit in the process so it'll be a couple days before I get everything put back together. At least i greased the pins this time around.