brake flush & bleed

[WNYsporttrac03]

03 sport trac xlt 4wd

i replaced two calipers and had some nasty contaminated brake fluid so i flushed all the lines at the same time by leaving the lines unattached and pumping the pedal.
installed the two new rear calipers, fronts are still ok, and bled all four, one at a time, a few times but the brakes still feel very spongy. they will actually work but not until the pedal is almost to the floor.
bled them by instructing my helper to push the brake pedal while i open/close bleeder valves while truck is running.
what am i missing? big mistake leaving all four lines open at once? need an abs digital tool to make sure thats ok? might just still have air in the lines/mc and have to bleed it as many times as necessary?

 

[Fredness]

Umm...
There is air in the system.
You can't leave a bleed screw open (let alone all 4) as air will get in.
I use a pressure bleeder that puts 10PSI or more on the master cylinder to force fluid throughout the system.

Look up manual brake bleeding, you want to start with the LONGEST line (back right normally) and work towards the closest (front left normally). The ONLY time the bleeder should EVER be open is when there is PRESSURE on the system - either external (like I do) or with someone holding the pedal to the floor. If the pedal is pumped or released with the bleeder open you will pull air in to the system - possibly even reaching the RABS/ABS and really causing trouble.

 

[koda2000]

It's called "gravity bleeding". I've done this on the front when replacing calipers and working alone. As long as you do one caliper at a time and make sure to keep the master cylinder reservoir full and DON"T pump the brake pedal, it works because the bleeder valve is at the extreme top of the caliper. If brake fluid is flowing out, air doesn't get in. I've never tried it on rear calipers or wheel cylinders. If you pump the brake pedal air will get sucked back in when to lift your foot. To bleed the system by pumping the pedal you either need a helper to close the bleeder valve before the pedal's up-stroke, or a check valve to prevent air from getting sucked in.

BTW, if you manage to get air into the ABS pump you may need special equipment to bleed the air out.

 

[Fredness]

You can "Gravity Bleed" all you want - provided it is "closed loop" - otherwise it's risky.
i.e.: Bleeder to a clear hose to a clear container with fresh fluid - No bubbles.

 

[swshawaii]

Oops! Should be titled "How NOT to brake flush & bleed". Not mentioned by the OP, but sounds like the MC reservoir ran dry.

 

[Fredness]

^^^

That being said, here is what I use:
https://www.ecstuning.com/b-motive-...er/motivepb/?gclid=CNST4dC_gM8CFdcYgQodOsQPQQ

Here's the DIY Version:


Ford Heavy Duty Brake Fluid from a FRESHLY OPENED container (only, ever).

Make sure you have a couple of the containers of fluid handy and repeat this every 2 years or as needed. In WA with much higher humidity that TX I was flushing every year. That's one of the ways I got 140K on my factory Explorer calipers and 220K on my Focus.