I pulled the truck into the garage a couple of weeks ago..To remove the rear tires to have them replaced...Just curious, I removed one of the rear drums, and the shoes were low..So I decided to do the brakes over...New shoes, hardware kit, wheel cylinders, all new lines metal and rubber..After the rears were completed, I went up front and went through the whole front system, Pads, rotors, calipers, lines rubber, and metal..I also replaced the metal line from the combo valve to the front drivers side hose that feeds the front calipers..So now the problem starts.. I bleed the system, and the pedal fades to the floor..I then replaced the Master Cylinder, and bench bled it before installing..NOW, I bled the system again, and I am still getting air out of the front..I removed every line I replaced and teflon taped them..There is no visible leaks on any of the lines...When I bleed the brakes with the truck off, the pedal stays hard, as soon as I start the truck, the pedal fades...

Any suggestions would be greatly appreciated...I will I had stock in brake fluid, I been through about 2 gallons on this bleeding

 

Well first of you should NOT use teflon any of the fittings... All fitting should be double flare fitting and not require any sealant.

Second if the pedal is fading out on you means you leaking pressure some where either internally or externally. So I would wash the whole underside of the truck with water really good and let dry. Then drive it up on ramps or jack it up on stands. Then get a buddy looking for the leak as you pump the pedal.

If the leak is internally there will be no fluid loss. Externally you'll have fluid loss (Resevoir will empty)

 

did you check to make sure that the wheel cylinders in the back arent leaking? you could have gotten a bad one.
also you shouldn't have had to use teflon tape on the compression fitting for the brakes they have built in ferrels.
I just changed my front lines the other day because of a collapsed line on the driver side. go to advanced auto and get the one man speed bleeders put them in. while bleeding put a clear hose on the bleeder valve and get a jar bleed into jar watch for air

 

Or make your own speed bleeder with a mayo jar and a piece of clear tubing...

Here is a pic of my setup on my 2002 Dodge (Rear disc - Yeah I know...)

 

I just blocked the line going from the combo valve to the drivers side brake line that crosses over to the passengers..So I eliminated the front brakes totally..I started the truck and the pedal stayed hard, Now, everything in the front brake system is brand new..And I have no visual leaks in the front at all..

 

i don't know, but you may have air in either the combo valve or the abs control.
i don't know what to do about it, but its all i can think of.

dumb question, have you tried bleeding with ignition on, when pedal is weak ?

 

I just got done bleeding the fronts again..This time I tried running a clear hose from the bleeder right to the master cylinder..getting rid of any air possible.. And the caliper is still spitting bubbles..

 

You have a defective part(s) or plain and simple a leak some where that you are not seeing.

 

Has anyone ever heard of a new rubber brake line being bad,,thats the only thing that can be bad..the caliper is holding pressure

 

Recheck all your fittings, it could be that you messed up a thread which is causing your leak. The worst thing you can do is think something is working without checking it.