Need help bleeding brakes

[mc1984ss]

can't believe I need to ask for help with this but I need help. Complete new system front to back every thing started out dry. Bench bled master cylinder, with vac pump started at furthest wheel and pulled fluid out wheel cylinder till no bubbles. Did the other rear then the two front calipers the same way. Drew a ton of fluid out and looked like I got most the air out as well. Go to press the peddle...... nothing!!!!! Zero pressure. Start back again at furthest wheel with vac pump now I can't get fluid out. What is the proper method with a vac pump? Keep the bleeder open and keep pumping? Or do you keep the bleeder shut, put a vacuum on it then crack it open? Is the master cylinder lid supposed to be open or closed? Thanks in advance, I've don't this before just never with a vac pump.

[icemanrd19]

That is exactly what I did and I did the same method getting the dot 5 out. Open up the rear bleeder and let it gravity bleed. It’s going to take awhile to get all the air out. You might have to repeat the exact process 3 or 4 times before it’s fixed

[Build-It-Break-It]

I've used multiple bleeder systems and the best method is your friends foot on the brake pedal and you at the bleeder. Never had a problem in 20 years of bleeding brakes.

[mc1984ss]

Gravity bled all 4 corners again. Front flow slowly but steady but the rear bleeders are a slow drip. Pedal is still absolutely soft, zero resistance. How do I determine if the master is junk? It's new but that could be a bad thing

[k7king]

OP do you have a brake booster? If so check the rod
gap between the boooster and the master cylinder.

[mc1984ss]

The car does not have a booster. I just converted it to manual brakes. The pushrod is just barely touching the piston on the master cylinder. Last night I removed the lines from the master and plugged the holes. I then pressed the brake pedal and it is firm. That should rule out a master cylinder problem. My assumption is I have air in the system somewhere that I cannot get out. I think I mentioned previously that the fronts gravity bled a slow steady stream but the rears have a very very slow drip with a pause between drips. I also discovered a slight drip of fluid out the front plunger on the proportioning / combination valve. The pedal is so soft there is zero resistance. I do not think the problem is with the valve but could be wrong???! My guess is lots of air in the system somewhere

[a67]

Air gets trapped in the combo valve and other high spots in the system. BTDT. Using vacuum bleeding works well to change the fluid in an already filled system. But in a system with air in it, the air expands (lower pressure), and doesn't want to move.

I ended up pressure bleeding from the lines that attach to the M/C. Pressure bleeding frightens me a little as a small leak or such can ruin a lot of good paint.

So I removed the lines from the M/C, plugged the M/C ports, and attached the pressure bleeder directly to those lines. That did the trick.

Also, if using an adjustable proportioning valve, set it for maximum rear pressure prior to bleeding.

Bob.

[Vimes]

The car does not have a booster. I just converted it to manual brakes. The pushrod is just barely touching the piston on the master cylinder. Last night I removed the lines from the master and plugged the holes. I then pressed the brake pedal and it is firm. That should rule out a master cylinder problem. My assumption is I have air in the system somewhere that I cannot get out. I think I mentioned previously that the fronts gravity bled a slow steady stream but the rears have a very very slow drip with a pause between drips. I also discovered a slight drip of fluid out the front plunger on the proportioning / combination valve. The pedal is so soft there is zero resistance. I do not think the problem is with the valve but could be wrong???! My guess is lots of air in the system somewhere

You may need to just start cracking open lines, front to back, and see if there's a spot where you get expected flow here, but not at the next point. Should be master cylinder, combo valve, rear flex line to axle, then rear calipers/cylinders. If you're dripping, you may also be sucking air.

[Hotwire]

You most likely tripped the valve in the combo block using the vacuum bleeder.

This is the operation of the combo valve:

https://youtu.be/qPLaPv8DITE?t=90

Watch that, then scroll to 3:00 and you'll see that you need to block the valve when you bleed the brakes.



Hope this helps!