Bleeding new lines

[sauldgold]

Ok, I'll start off by saying I've read the shop manual and all of the relevant threads multiple times.

That said, I recently replaced all caliper seals and pistons and installed new steel brake lines all around.

Then of all the methods I've read about, using a big syringe to inject the brake fluid up from the caliper through the lines and into the MC seemed the most logical, so that's what I did.

And yet for the life of me, I could not get any brake pressure - not even on the single right side front caliper / cylinder.

I then thought maybe somehow some air got into the caliper and so I bled the caliper a bit from top down -- not a single air bubble and still no brake pressure.

So after a lot of swearing and throwing wrenches at the wall, I finally decided to tap out and call it a night.

This morning after re reading the "how to" threads yet again, I noticed one guy wrote to depress the brake lever and tie it down before pushing the fluid up through the line.

I missed this step (regardless both MCs filled up easily)

So my question is:

Is not depressing the brake levers before injecting the new fluid where this whole process went wrong, and if so why?

If not that, what else is going wrong here? (all of my fittings are tight, no leaks anywhere -- I'm stumped)

For reference it's a G5

[RinkRat II]

  Open the line at the master cyl and depress the lever several times with your finger on the outlet side. sometimes the piston will travel too far and won't return all the way to pick up more fuid. Thats where I'd start. My$.02

      Paul B

[flower_king001]

I have had great success every year using a MityVac to bleed my lines.

I have also done this in the past if subborn:

https://www.youtube.com/watch?v=MQtT3XpB_B0

If none of the above doesn't work I would say you have a problem somewhere in your rebuild.

[gearman]

  Open the line at the master cyl and depress the lever several times with your finger on the outlet side. sometimes the piston will travel too far and won't return all the way to pick up more fuid. Thats where I'd start. My$.02

      Paul B

Yes make sure your mc is working.

[wirespokes]

Bleeding the master first helps a lot.

Do realize that if there's a high spot in the system, the air will rise to that spot and be trapped there. So if the line arches up, then back down, the air won't ever leave that high spot. Jiggle the line or even unbolt the system so the only high spot in the system is the master cylinder or the bleed port.

When filling the system from the bottom, there's no need to hold the lever to the bar. I've filled brake systems from the bottom and still have problems bleeding, so don't do that any more. I just fill the reservoir and leave it at that.

When replacing the brake fluid (once every year or two) no special operation is needed. Empty the reservoir (siphon it out with a turkey baster) and fill with fresh fluid. Open the bleeder at the caliper and let the fluid flow out. Don't let the reservoir run dry or you'll have to bleed the master. Once fresh fluid comes out the bleeder, the job's done.

I've never figured out why strapping the lever back to the bar over-night works, but it does.

[pehayes]

Back off your linkage adjustments to ensure that the MC piston can fully retract.  If it doesn't retract fully then it won't transfer fluid from the reservoir into the line system.

Patrick Hayes
Fremont CA

[guzzisteve]

For years & years I took calipers off and put them on a table next to bike w/hand wrench between pads. Front & rear calipers above the master & high point/center frame under tank. Rear only has to be above the integral splt valve. Same with front brake, take off, on table above master with lines going on upward slant.

[Huzo]

I can't fathom how depressing the lever ond securing it, will be advantageous.
I thought that would only block the communication hole between the reservoir and the lines. I've NEVER done that and cannot see the logic.
I understand why holding the lever in the actuating position is useful to prevent inadvertent actuation when calipers are off. This prevents popping the pistons out of the calipers, but I think that's the basis of that logic, not when performing bleed function.

[Huzo]

Ok, I'll start off by saying I've read the shop manual and all of the relevant threads multiple times.



Is not depressing the brake levers before injecting the new fluid where this whole process went wrong, and if so why?

Yes it probably is, for the above reason.

[Rebochi]

   Go straight to Harbor freight and pick up one of their 10 dollar brakeline bleeding hand vacuum pump. Hook it up tp one of your brake bleeds, fill the reservoir and start pumping. It will pull fluid through the master cylinder and the caliper.  It will take less time if the pistons are fulling retracted when you start.

[Huzo]

Remember the tiny communication hole MUST be able to transmit flow between reservoir and system or you'll be rooted.
If there's a bubble in the lines, how else would it migrate up to the m/c and into the reservoir to dissipate ?

[wymple]

Get one of these, never look back. Only takes a minute or two, a 5 year old can do it.

https://www.ebay.com/itm/2-In-1-Brake-Bleeder-Vacuum-Pump-Gauge-Test-Tuner-Kit-Tools-DIY-Hand-Tools-Hot/401408083438?epid=579845735&hash=item5d75c945ee:g:9BAAAOSwb7NZwXJ2:rk:3:pf:0

[wirespokes]

I can't fathom how depressing the lever ond securing it, will be advantageous.

I know what you mean! I have NO clue why it works, but it does. Try it sometime, you'll be amazed. It's one of those things that defies logic. I never would have thought of it - read about it somewhere and tried it one of those times when I couldn't eliminate that last little bit of sponginess. Damn if it didn't work!

[Huzo]

I don't dispute that your observations are honest so please don't think I'm calling you a liar or a fool..
I am not, but..
If you have air in your system and all the unions are secure, are there not only two places that air be purged ?
Either the air can migrate upwards and through the tiny port into the reservoir and float to the surface as we've all seen innumerable times, or it can be pumped through the lines when the bleed nipple is opened..
If you have the lever depressed, how can the air pass through the m/c and into the res fluid...?
It just bloody well can't, unless you have an anomaly in your master cylinder.
If you have managed to expel air from a properly sealed system while securing the lever to the 'bar, you have succeeded despite this not because of it, but the air WILL NOT HAVE BEEN PURGED THROUGH THE MASTER CYLINDER if it is in serviceable condition.
I would like to hear from Rodekyl or Roper on this specific issue.

[jwinwi]

I will always remember what an enormous PITA it was bleeding the integrated line when I installed frentubo lines and freshly rebuilt calipers. A mityvac or decent copy makes the job almost tolerable. What finally did the trick was raising the master cylinder to the high point of the system and pumping the master cylinder with all bleed nipples closed. The air bubbles have a clear escape route when the mc piston retracts.

[wirespokes]

Yeah, I know what you mean Huzo! And I wasn't feeling attacked - I understand completely where you're coming from. I'm in the same boat, except I've tried it and know it works.

My best guess - the pressure somehow dislodges air bubbles to come to the highest point. They, of course, can't escape, not until the lever retracts. So when the lever is unbound, the piston goes to the resting position, the return port opens and the air bleeds out. That's my guess.

I also have had good luck letting the lever snap back to the rest point. I think it shocks the system and the vibrations dislodge air bubbles.

[Huzo]

Yeah, I know what you mean Huzo! And I wasn't feeling attacked - I understand completely where you're coming from. I'm in the same boat, except I've tried it and know it works.

My best guess - the pressure somehow dislodges air bubbles to come to the highest point. They, of course, can't escape, not until the lever retracts. So when the lever is unbound, the piston goes to the resting position, the return port opens and the air bleeds out. That's my guess.

I also have had good luck letting the lever snap back to the rest point. I think it shocks the system and the vibrations dislodge air bubbles.

Ok then..
So in that case, it is that you have left it sit long enough for the bubbles to float up to the piston, ready to be dragged backwards when it retracts.
If that is the case, then going away for the same period with the lever out,  would have resulted in the same bubbles following the same path, but instead of coming up against the depressed piston, they would continue on and arrive under the communication port and subsequently float up into the reservoir.
One would need to make sure though, that the system was oriented so as to allow the bubbles to always rise on their journey.
This aspect has been covered already on this thread.

[earemike]

I know what you mean! I have NO clue why it works, but it does. Try it sometime, you'll be amazed. It's one of those things that defies logic. I never would have thought of it - read about it somewhere and tried it one of those times when I couldn't eliminate that last little bit of sponginess. Damn if it didn't work!

Has worked for me in the past (or seemed too). If you have the time no harm done, I used to tell myself it gave any small bubbles time to slowly migrate to the reservoir.

Then there’s reverse bleeding and fancy bleed valves to help too.

[Perazzimx14]

Reverse bleed the brakes. A $4 syringe and a $0.01 in 1/4 aquarium tubing and 5 minutes and your done. No bench bleeding or expensive vacuums or speed bleeders to buy and you are injecting fluid from a low point and forcing the air upwards the way it naturally want to go. Up and out.


I totally rebuilt the linked brakes on my T3. New lines refinished the calipers and installed new pucks and seals. I fretted the entire rebuild as I had worked with linked brakes before and know hw huge a PIA they are to get all the air out. I was done totally bleeding the brakes front and rear in 20 minutes and only using 1 pint of fluid.