Bleeding Troubles

[texasz]

I've installed new calipers, rear wheel cylinders, pads, shoes, drums, discs, rear brake hardware, braided stainless lines at all four corners, 8.5" brake booster, and 1" Wilwood master cylinder.  No fluid seems to be moving!  I started at the rear corners (checked both) and no fluid coming out when brakes are slowly pumped (by my son).  I then moved directly to the bleeder ports on the Willwood master cylinder and no fluid coming out when brakes are slowly pumped.  I can hear air movement in the booster.  I unbolted the master cylinder and pulled it away from the booster just enough to see the rod and had my son barely press the brakes just to confirm that it is moving...and it is.

 

What am I missing?

 

[gnosez]

You need to bleed the MC first which you can do either on the bench or in the car.  You need to be able to see fluid come out of the MC and it will be messy so plan accordingly. You also might have an issue with the rod being too short to completely compress the MC.

[Zed Head]

34 minutes ago, texasz said:

 no fluid coming out when brakes are slowly pumped (by my son). 

I unbolted the master cylinder and pulled it away from the booster just enough to see the rod and had my son barely press the brakes just to confirm that it is moving...and it is.

Why slow and why barely?  I'd give a few good full pumps.  It's new so there shouldn't be any crud in the bore to worry about.  It should just squirt a bunch of fluid.

Actually, to get picky, you were supposed to run the plunger through its stroke while it was off to bench bleed it.  Bench bleed, install, continue system bleed.

[texasz]

When installing the master cylinder I test fit and adjusted the rod until it no longer depressed the piston at all when installing the master cylinder (it just barely touches the piston).  This allows the piston to fully disengage/close when the brake pedal is released.

 

Reason for just barely pressing the brake with the master cylinder out of the way was I just wanted to confirm that it was moving and I am not 100% sure that pressing it all the way would not have caused problems (after reading about people's challenges with the reaction disc I'm probably just being overly cautious).  

 

I've read that bench bleeding the master is not required, while many do recommend doing so.  Not doing that would just push more air into the lines right?  What about using the bleeders on the side of the master (as I described in my first post)?

[Zed Head]

One thing that I've found helps when bleeding brakes is to just think in terms of fluid and bubbles.  You can bench bleed and do it wrongly if you have the wrong end of the cylinder up.  Just be aware of where the air is and try to fill everything with fluid.   And full strokes help because the bubbles will always hide at the top-most little spot.  Imagine what's in the MC - the ports that head out to the front and rear ends is at the bottom.  The bubble will be at the top.  And, bubbles compress, so a slow incomplete stroke can just compress a bubble over and over again.

Be the bubble.

[gundee]

I have done this many times now. This is my best method I have found.

First get fluid to bleed out the master cylinder bleeders.

2. I then open all 4 wheel bleeders and let gravity push fluid until they start to drip fluid.

3. Then close up. You can then usually get the air out with the normal pedal stroke method.

Unfortunately if you try to adjust that rod like you mentioned, it usually lets the reaction disc fall out.

[gnosez]

He's using an aftermarket Wilwood MC and the rod is not always at the right length when you take them out of the box. 

[texasz]

Did some further investigating on this today. I attempted to bleed the fronts and was getting air then fluid flowing through the fronts. I then turned my attention back to the rears and still nothing...no air, no fluid. Since I was already back there I thought I'd crack the line before the proportioning valve (mine is in the rear) open a little bit to see if there was air/fluid at least getting pushed that far through the system. Unfortunately I was unable to loosen the nut, I did spray all of them back there with some penetrating oil before putting things away for the day. Everything in this area was bone dry though so no leaks there.

I also felt around the fittings under the master cylinder and the distribution block under it to see if there was any leaking there and it all seemed to be good.

[Zed Head]

On 12/20/2020 at 11:16 AM, texasz said:

Did some further investigating on this today. I attempted to bleed the fronts and was getting air then fluid flowing through the fronts. I then turned my attention back to the rears and still nothing...no air, no fluid.

Did you ever get pressure through the MC bleed valves, maybe with a more vigorous pedal pump?  That's the starting point.  No pressure there, no pressure anywhere.

[texasz]

Update....I have brakes!!!

 

Short story, I managed to get the Z up to the local Z shop and get some help.  There were a couple things working against me, there was still some air in the master cylinder that I had not managed to get out and probably much more impactful was that the rear wheel cylinders were not adjusted out far enough to properly engage the drums.  As he explained, if the shoes are not making proper contact with the drums then there is no pressure in the system and thus bleeding cannot happen...once explained it was like a DOH! moment as it made perfect sense.  😉  

 

So it is back in my garage now and ready to move on to the next part of the project.  Yipee!!