rear disk brake swap done, now no brakes

[MUDDING B-3000]

Alright well heres my problem i did the rear disk swap on my 92 ranger i got full width D44 9" i put the chevy 1/2ton disk brakes on the rear, bled everything with the truck off its all good no air, pedal firms up just before half way.

But once i start the truck up a baby could push the brake pedal all the way to the floor no pressure what so ever. The master cylinder is under 6 months old. ive bled the system over an over but i still cant get any pressure at the pedal with the truck running. what could cause this?

 

[RangerSVT]

Do you have RABS?? You might want to bypass it...Try bleeding them again...
SVT

 

[doyouquaxu]

try bleeding them with the truck on

 

[MUDDING B-3000]

i did bleed them with the truck on an didnt do anything it wont build pressure. an is the RABS the module in the frame rail that the lines go in before it runs to the back brakes

 

[RangerSVT]

Yes, thats it...If it won't build pressure, check your brake master cylinder and make sure its filled with fluid, and doesn't run out when bleeding (though you might already know this, just verifying!)
SVT

 

[kris97ranger]

svt i dunno if it matters but he had this whole setup last season with the rear calipers siezed. and it was good now he has new calipers and this problem.

adam correct me if im wrong just figured extra info may help out

 

[MUDDING B-3000]

ya when i did the swap last fall the calipers i had seized up so i pinched the rear line off an drove the rest of the season with front brakes. but ya i went an bought new back calipers bled them an boom now this happens but i was thinkin back an there was a fair time period where i had both lines off the master when i was re flaring the new lines an im not 100 percent sure if the master completly leaked out over night an threw the nxt day, which would of cause air to get in it, i went to bleed the master its self tonight got some air out of it an went to re flare the lines back on an broke my flare tool so gotta wait till tomorrow to return my 2 day old broken flare tool

 

[bilzy7]

Nice. Love breaking tools...

 

[Sasquatch_Ryda]

Just making sure...but did you get the calipers mixed up side to side? Is the bleeder screw ABOVE the banjo bolt and brake hose?

 

[Snurfer]

^^^ absolutely. the damn bleeder screws gotta be above the brake line flange. if thats the case, swap em and bleed the breaks again with the motor running and youll be set

 

[RangerSVT]

Since you had the lines pinched off, it is possible that the RABS module seized as well. First thing I would do, as stated above, is make sure you have the calipers installed on the right sides (bleeder valve up), then finish flaring the lines, while your at the store, grab you a couple of brake line couplers so you can bypass the RABS if needed, take and bleed the whole system and get back to us and let us know how it went
SVT

 

[kris97ranger]

then go to ardbeg in two weeks and see what you can break

 

[MUDDING B-3000]

alright so i deleted the RABS put a coupling in bled the system with the truck on an off still nothing, yes the bleeder screws are on top of the caliper. im gonna try re flaring the lines an hookit back to the master an re bleed the system an see. I talked to a buddy whos a mechanic an he was saying i should pinch off the rear flex line an see if the brake system works propertly an if it does then the master cylinder is not big enough to supply that kinda pressure to all 4 big calipers

 

[breidhaupt]

you may need a bigger master cylinder and adjustable prop valve to send more pressure to the back brakes. you did swap from drum brakes? cause if so the drums required less pressure to engage than disk brakes so that might be your problem as well. hope this helps.

 

[MUDDING B-3000]

ya that seems to be the same answer everyones saying that i need a bigger master cylinder, what style could i swap in? like one from an explorer that has factory 4 wheel disk brakes?