Bleeding/flushing brakes (and bench bleeding MC)

[MaineShark]

Okay, I'm going to replace all four brake hoses, and my master cylinder. I'm going to flush clean DOT4 through the system at the same time. I have a few questions:

First, I'm trying to decide the best way to flush and bleed the lines. I have a vacuum bleeder, those bleed screws with the check valve, and I can build a simple pressure bleeder, if y'all think I should. I need to get the old fluid out, the new fluid in, and then remove the air. Should I drain the system, then fill with new fluid? Or should I use the new fluid to push the old fluid out? In any case, do you recommend the vacuum or the pressure? (the check-valve screws are just there for added insurance - I'm never going to pedal-bleed these brakes again )

Second, I understand the basic theory behind bench bleeding the master cylinder, but I'm somewhat stumped on a couple points: how do I get the master from the bench to the car, without losing fluid (or will it not drip enough to matter)? And, if I'm pressure bleeding anyway, do I really need to bench bleed the master, or will the pressure bleed take care of it?

Joe

 

[clar2001]

I allways bleed the master on the car with the little hoses they supply then unscrew and hook up the brake lines with minuial dripping . Allways keeping a rag underneth.

Do the new master cylender first fill with fluid ,then when you remove your brake hoses one at a time the fluid will just run out keeping your cylinder full ,by the time you do all 4 and bleed your brakes very well,you will have exchanged brake fluid.

I usly vacum bleed my brakes then put the lid on and have some one stand on the peddle and pressure bleed to finish off.

Will you be installing a new ajustiable proportioning valve .

 

[Bob Chadwick]

Bled my MC on ther bench. Not a problem. The unit is a "sealed" system and you won't loose much.

I paid $69 to have the whole system bled at Firestone. I started to do it on my own and it was a PITA. Between removing the wheels, etc. They had the professional machine and did a great job. I just got it to stop and took it over to them.

 

[76L82]

I went through the same ordeal when I replaced all four calipers and brake hoses. I got my best results...good solid pedal....when I left the fluid in the master to start with and then progressed using the power bleeder at each corner.

After I power bled all four corners, I went and did a manual "pump and bleed". Using those bleeder screws was a huge help.

Like was said by clair2001, you might want to replace the proportioning valve while you're at it...I completely re-bled my brake system...resulting in a very spongy pedal..more than 4 times before I narrowed it down to a proportioning valve problem. Changed it and what an unbeliveable difference!