you then I would guess have a pinhole in a brake line,a bad/loose connection/flare that is deformed/ bad rubber hose.Look at the simplest first. Look the the flares where you connected to the MC, if they deformed they may not be sealing like they should. if that is not it,then trace out each brake line and look for pinholes,etc and inspect the rubber hoses.

 

Any air can cause issues in brake failure. I assume by spewiing you mean you constantly have air bubbles in the front that you can not clear. If your year truck is like my 91 you have a hard line that goes from the master that crosses over to both wheels in front. From there you have two rubber lines that go from the hard line on both sides to the wheels. If you have no leaking brake fluid the hard line is probably good. Next in line are the rubber hoses that go from the hard line to the wheel calipers. Those rubber lines can have issues inside them that you will not be able to see and failure is fairly common. If my truck I would replace those two rubber lines and bleed the fronts again. You don't have to do the rears at this point. If you still have the spewing air in front and new rubber hoses, and no leaking hard line, the booster is almost sure to be the culprit allowing air to enter the line. Sandy

 

Resolved? I may have missed a post. Are you pulling a vacuum? Easiest way to pinpoint a leak..You can isolate components, fittings, ect.

 

old school diagnosis .the booster can also go bad an let the pedal go to the floor.
in the past year there have been at least 4 people that refused to believe a bad booster will cause the pedal to go to the floor. ....until they replaced the complete brake system including 2 or three master cylinders and finally replaced the booster and fixed the problem.

 

I have been gone all weekend. I'm going to start all over I will double check all fittings again then bleed the master first then the RR then LR then RABS then RF then LF If I have no luck I will replace the booster. I will let ya all know what I come up with. Thanks for all the help.

 

I double checked all my brake line connections (master, front lines and rear lines) then bled the master cylinder first, then RR then LR then RABS then RF then LF I now have the rear brakes working but the front do not and my pedal feels good when not running, but when running the brake pedal goes down quite a bit before the rear brakes start to engage, I think I must still have air in the front brakes somewhere. I wonder if it could still possibly be the brake booster. I will try bleeding the front again and see if that helps.

 

I think that is a good idea. If you cannot clear all air from the front lines, I would replace the two rubber lines running to the caliper if you haven't already done so and bleed the front again. If you didn't remove the master cylinder I would bench bleed it if you do replace the rubber hoses. If you still have air after that, I don't know what else it could be but the booster. Sandy

 

thanks for the info I will replace the the two rubber lines to the front and see what happens. I originally replaced the master (I bench bled before installing) and the two rear brake wheel cylinders, when I did I broke one rear brake line and replaced it also. the confusing part is I had way better brakes before I started, that is why I don't think it is the booster.

 

I totally understand the confusion, I just went through something similar. I know you have done a lot but this is all I know to do at this point. What I mentioned in my last post totally runs me out of ideas other than the booster. anyway since you are replacing the rubber lines which is a great idea let's see what happens. I wish you the best of luck, let us know .Sandy.

 

it will be a few days until I can back to working on my truck but I will keep you posted.

 

If you've gone through 1 gallon if brake fluid you should just look for the massive puddle of brake fluid. If not I bet your booster is full of brake fluid. If you have a bed seal on the master and can fill up the booster.

 

were you able to figure out if it was a bad seal? Had a similar issue.

 

The 1 gallon of brake fluid I went thru was bleeding the brakes not from leaks. I also replaced both front rubber brake lines and re bled everything in the correct order RR, LR'RABS,RF,LF and I still have next to no brakes.
I am going to unhook the brake lines from the master and re bleed it and then I am going to install plugs to see if the master pumps up then I will know if I have a defective master cylinder if the master is good I guess I will install a new brake booster.
Thanks for all the input from everyone it will take me a few more days to get back and let you know what I figure out

 

Are the rear brake shoes adjusted to take as much free play out of them as possible? I usually crank them in until the drum can't be turned by hand and then back off slightly. If this isn't done it is entirely likely there isn't enough fluid volume in one stroke of the pedal to activate the rear brakes and the pedal will go to the floor, the front brakes could be perfectly adjusted but it won't matter there won't be any braking power.

 

I just had to walk away from my truck for a long time (a few months). But i went back I finally got brakes here's what I did. I disconnected both brake lines from the booster and plugged the booster where the brake lines hook to, so I could make sure I did not get a bad booster.(I started the truck) the pedal was hard (it felt like good brakes) then I hooked up the rear brake line and tried the pedal with the truck running and had good pedal again. then I hooked up the front brake line started the truck and the pedal went to the floor when I stepped on it. I bled the front and it never stopped getting air after many times of bleeding. so I unhooked the front brake line again and re hooked it up very carefully, bled the front brakes again and got a small amount of air out of each side then I had good brake pedal running or not. I can only presume when I hooked the front brake line to the master that I did not have it aligned straight and it was sucking air (I felt like an idiot) as I have changed many master cylinders before. This probably will not help anyone else but I wanted to let know.
Thanks everyone for their input it is much appreciated. Chief Maint.