So I noticed Thursday last week that my rear resevoir for my master cylinder kept getting low and/or empty and Saturday finally seen that it was dripping from the master cylinder. I have a 91 K5 with the 6.2l Hydro-boost system and this is the second time i have replaced. This time however I forgot to bench bleed the brakes before cussing out my truck and pumping the brakes for nothing for 45min. After properly bench bleeding and reinstalling the master cylinder I still have next to no pedal, just the last little inch or so actually slows and stops my truck. Should I bleed all my brakes at the tires now or is there possibly something else wrong?? Thanks to all who reply and have a safe one guys.

 

Definitely sounds like you still have air in the system. How did you bleed the master cylinder? You can do this by bending up some short lines to direct fluid back into the reservoir away from the ports to the master cylinder piston itself and bleed it in the vehicle (this is my preferred method). You then MUST bleed the rest of the system to get all of the air out.

Some MC's are hard to get all of the air out, even with repeated bench bleeding.

 

Well you nailed it on the nose swartl. The master cylinder was bled perfectly but I had air in the lines, after going around all four tires 5-6 times and a pint and a half of fluid I now have the best pedal I've ever had.