Brake bleeding problems

I installed a new flat handlebar for an 82 XJ650 maxim... therefore new ss brake lines and new MC for the flat bars. I let brake fluid drip down the lines overnight. When I press the lever I could see some fluid come out. Attached the bottom brake line to the caliper and opened the bleed valve. Press the brake lever and air comes out. Closed the valve, opened the lever, then opened the valve and it sucks the air right back in. Bought a mity-vac to pull the fluid. Will not pull the fluid through. Tried pumping with pressing the brake lever and nothing. Any suggestions? Any idea what I am doing wrong? Thanks for the help

 

Possible faulty bleed nipple?

 

It's not at the nipple. Definitely seems to be at the new master cylinder. I can pull brake fluid out of the first top banjo when disconnected from the MC

 

My problem seems to be with the master cylinder HCP1808WO I ordered from chacal.
When trying to bleed the brakes, it seems that pulling the lever pushes brake fluid out but then pulls it back (and holds the pressure when pulled back). I have not been able to bleed my system with a mity-vac (it sucks and builds pressure but nothing comes out, with or without the cover on the MC and brake lever pushing doesn't change anything). When pulling the lever I can hear air come out of the valve at the caliper, I then tighten the valve, release the lever, then open the valve... and it sucks all the air back in. I've also tried disconnecting the top line from the MC and sucking the brake fluid through there with success but to get a good bleed I need to have it coming from the MC. Is there a pressure release valve or something like that in the master cylinder that I am missing? My bike has now been down for a few weeks because of the brake lines etc and I would like to get it back going ASAP. Is this master cylinder crap?

 

Try this:

Connect line at MC
Using your finger as a valve, cover the banjo hole, squeeze lever to build pressure, then release finger.
Cover again with finger and repeat.
Make sure the MC stays FULL when doing this.
When you get fluid at the end of the line, attach at distribution block.
Attach line from block to caliper.
Repeat process with the next line before you hook it to the caliper.

NOTE: At no time should you release the lever before your finger is back over the hole.

My guess is there is a massive amount of air somewhere in the middle of the system that is not allowing the MC to pull the amount of fluid it should.

Try this, then if you still can't get pressure, contact chacal. I'm sure he'd be more than willing to give you more advice.

 

You say that you can hear air being sucked back into the system via the bleed nipple?? And you say this happens because you released the lever THEN opened the valve?? Well that's your problem mate. The sequence should be squeeze, open valve,close valve, release lever, pump and repeat. Not open the valve with the lever not squeezed. Unless I've completely mis read what you meant?

 

This is a normal operation of the disc brake system. The M/C sucks a slight bit back to release the presure from the brake disc.

When you open the bleeder valve after releasing the brake lever you are defeating the purpose of bleeding the system. Once the system is bleed out completely. There will be a very slight amount of pressure that is maintained in the system. The air you are hearing is that pressure releasing.

Follow the process outlined by tskaz, and absolutely do not relase the brake lever unless the line/fitting/bleeder is covered/sealed.

Ghost

 

I usually have no success with the traditional method of: squeeze, open bleeder, close bleeder, release, start over. I usually use a syringe (you can use your mighty vac for this) and PUSH the fluid back through the lines toward the master cylinder first. Then once you have the lines bled backwards you can use the traditional method to get a rock solid lever. Works for me everytime.

 

Don't forget to bleed again after 300 miles.

Bleed the top banjo, where an air bubble can hide.
Pump-up and hold pressure, crack the bolt loose, use a towel.

 

Thanks for the help guys. I think it is working now. One of the problems I had was that the screw that pushes the piston in on the MC from the lever was screwed too far in not allowing the piston to fully return. 300 miles and it will be checked again... probably even after the first ride

 

Ah ha...wouldn't have thought of that one!