Hello,
I am new to yotatech. I need help from some experts. I am having problems with brakes. I replaced brake booster, master cylinder, front rotors ,calipers ,pads ,rear drums, shoes and springs. I have vacuumed all the lines out all the air out. I have no leaks. When the truck is off I build pressure on the brakes but as soon as the truck starts pedal goes to the floor and I have 0 brakes. Any information or advice would be greatly appreciated.

 

Did you bench bleed the master cylinder prior to installing it?
when you say you vacuumed all the lines do you mean your bled the brake lines?
what order did you do it in and did you bleed the LSPV too?

 

So I did bench bleed the MC, I bled the brake lines first normally the with a vacuum pump. I did not bleed the LSPV

 

Check the pedal is adjusted properly. If the bar that goes through from the pedal to the MC isn't adjusted correctly, the proper length and throw, it can do this.

Could it be that when you did the vacuum pump bleed, you let the MC get low on fluid and it sucked air into the MC? Personally, I would do the bleed on the whole system again, but without using the vacuum pump. Right rear, left rear, right front, left front, LPSV.

Since you didn't bleed out the LPSV, it's entirely possible you still have air in the lines. I would do a complete system bleed again, without the vacuum pump. See above for the correct order. Again, don't neglect the LPSV. It matters to the whole system. You might consider pulling the bar, from the LPSV to the axle, off at the axle end, and move the LPSV through it's entire range, to ensure there's no air, or gunk, clogging it up. Then reattach the bar to the axle, and do the system bleed. It might help.

Good luck, and let us know how things work out for ya.
Pat☺

 

Did you put your calipers on the wrong sides? Bleeder valve needs to be on the top or you'll never get the air out.

 

I use a vacuum bleeder. I have to put a bit of grease around the bleeder screw threads or I’ll get air bubbles forever.

curious. Did you have this issue and replaced booster and master trying to fix, or did this problem only occur after they were replaced?