HELP! Cant bleed brakes!
 

Just replaced the master cylinder and proportioning valve on my 85 K20 suburban. Pedal had been inconsistent and based on a couple other threads I decided to pull a proportioning valve out of a parts 84 C20, and install it along with a new master cylinder since I had to bleed the brakes any way. Got everything all reinstalled, and I set up to vac bleed the system out. Started with the right rear drum, loosen the bleeder screw, pull 20Hg/in vacuum, and 0 fluid flow. WTF??? Ive bled alot of brakes and teach students how to as well, as a teach a basic autos class at times. Everything worked OK pulling it into the shop, but this has got me puzzled. Any ideas???
--Mike

Re: HELP! Cant bleed brakes!
 

Has that proportioning valve been tripped?
Did you bench bleed the master cyl?

Re: HELP! Cant bleed brakes!
 

Bench bled master as i always do.... no idea if prop valve has been "tripped".... is that fixable?
Mike

Re: HELP! Cant bleed brakes!
 

If its tripped it needs recentered ...and theres a tool that holds it centered while bleeding

Re: HELP! Cant bleed brakes!
 

There are better vids out there..just look ...
https://m.youtube.com/watch?v=xrjENVu1Bxk

Re: HELP! Cant bleed brakes!
 

I've been told you can recenter the combination valve by slamming on the brake pedal pretty hard but never had success. That screw in bleed tool is what you need though once you get it centered back. If you do not have that tool you can still bleed them just just have to bleed slowly instead of jamming on the pedal as usual.

Re: HELP! Cant bleed brakes!
 

I had a pain bleeding my brakes and I rebuilt the entire system - lines and all. Someone gave me some advice on the site to build a pressure bleeder and that solved my problems. If you want search up my post history and you'll find it in there.