Pump the lever, hold it closed and tie with a zip tie and leave that way over night. Air also sometimes get trapped at the banjo fitting, while under pressure, crack and retighten the banjo fitting.

 

I only have automotive experience but here are my thoughts. My first clue was that you took apart the master cylinder. Now, mind you I have never taken apart a motorcycle master, but, would it be possible that you re-installed / assembled the plunger assembly / cup backwards? This would account for the system having "backwards" vacuum drawing air back in when bleeding the master as opposed to drawing down the fluid into the bore. This would also account for your inability to vacuum bleed the system from the caliper. It almost sounds to simple but at the same time possible?

As an afterthought, you really shouldn't "tape" any threads in the brake system. It's a recipe for disaster.

 

didn't see if you tried this, but check the new line make sure it's not clogged or broken down inside....

 

This would make sense. By your description (no fluid flowing and vacuum after actuating the lever), it sounds like something in the m/c is backwards.

 

I bought one of these One Man Brake Bleeder from Harbor Freight for $6 to use in my part time ATV business. Saved me tons of time and aggravation.

 

It sounds like the m/c is put together wrong or you have a blockage or a leak. Take it all apart and make sure the m/c is good. Blow through the lines to make sure they are clear. Make sure the pistons in the caliper are free by pushing them in and out. Hook it all back up. Open the bleeder. BTW: it is OK to put sealer tape on the bleeder threads. It is actually needed to keep air from leaking past the threads. With the bleeder open, fill the reservoir and slowly pump until you get fluid coming out the bleeder. Now close the bleeder and slowly pump the lever until no more air bubbles come out of the hole in the bottom of the reservoir. This is all that you usually need to do. The brake can be bled from the top. The next best way is to push the fluid up from the bleeder with a syringe full of fluid. If the first method doesn't work, you have a leak or the m/c is not working properly. Clean all of the fittings with brakleen and dry them then check for leaks with your finger under the fitting, if your finger gets wet, you got a leak!

 

This sounds like the next step I'd take in trying to resolve your issue ... I too ( like you ) am a ASE Tech ( although a very old one .. It was NIASE first ) and this wouldn't be the first time I've seen problems with a "brand new hose" ... It only takes a few minutes to disconnect and check and even if it isn't the problem at least you've eliminated once possible part of the system.

 

I tried all the suggestions I could find on the web. Nothing worked. Got a Brake Bleeder from Harbor Freight for cheap and had them working in 5 minutes.

 

+1! When all else fails this method has worked several times for me.

 

Let me start by saying Thanks, I didn't expect 18 replies so quickly. I'm surprised by the eagerness of people to help. Makes me want to add a HD to the stable.

All the advice is solid, I selected the posts that hopefully would reply to everybody.


The MC not letting fluid into the lines is exactly what's happening. With the system under Mityvacuum at the caliper if I slowly squeeze the brake lever it will more rapidly advance the froth into the line, and then when I release it will halt for a few seconds until the Mityvac overcomes the vacuum pulled by the MC.


Back bleed up to the MC. Good idea. Doing this for sure.


The first disassembly was after I noticed the MC was pulling a vacuum on the brake system. Later in the evening I took it apart again to make sure I didn't miss something. It is physically impossible to assemble it incorrectly. The piston only goes in one way and I never actually removed the cup seal from the piston but that can only go on one way, too.
I've used a little thread tape on bleeder bolts many times before on ABS systems where the only correct way to bleed it is to pull a vacuum on the caliper. Never had any problems with that in the past as long as one is judicial in their application of the thread tape.




This has occurred to me. It seems wild to me that a Magnum brake line made here in the USA would have a manufacturing flaw. I inspected the line to see if fluid had leaked in between the plastic sheath and the steel braid and found nothing.
When I back-bleed the system with the banjo bolt loose at the MC I will know if there is a blockage in the hose.



I did not take the caliper apart and clean the pistons. I did, however, remove the caliper and gently press the pistons back into the caliper before starting the bleeding process.