Rear brake bleeding no fluid

[Rough75C20]

Hi all,

Attempting to bleed the brakes after full rebuild. Can’t get the rears to bleed or even fluid to the rear lines. The proportioning valve is centered at the moment due to me removing the switch and recentering. However I still can’t get fluid to the rear lines with a vacuum style bleeder. I tried just opening and stepping on the pedal but the valve moves and shuts off the lines to the rear. I tried just shoving a small screwdriver in there to keep the switch from moving but still no luck. I’ve seen the centering tools on the internet. Is this really needed? How did they bleed the brakes before these? If all it does is keep the switch from moving, why wouldn’t the screwdriver work? Not sure at this point what to try next. Do they sell the centering tools at parts stores?

[bd]

You don't need a centering tool, but the combination valve needs to be centered.  Did you bench-bleed the master cylinder before installing it?  If not, you should.  Try gravity bleeding the rear brakes - make sure you keep the M/C reservoir at least half full during the process or you will need to start over.

[Rough75C20]

Will try bleeding master cylinder. With the valve centered I took the rear line off and put my vacuum bleeder right on the rear line. It will pull vacuum, but I still can’t get fluid.

[bd]

Then there is a blockage somewhere.  Did you replace the M/C and/or booster?  Did you replace the combination valve?  Did you flush the lines using a solvent?  Crack the rear line right at the M/C while an assistant depresses the brake pedal to see if fluid escapes.

[Rough75C20]

There was a blockage in the final section of the rear line going into the new rubber line. This section of line wasn’t replaced and actually had a large hole as well. Will replace the line and give an update. I was able to pull fluid through the line up to the blockage, so replacing the line should allow fluid to get to the rear bleeders. Thank you!