Brake bleeding help!

Hi everyone,
I'm looking for help of how to bleed the brake lines.
I have a 1992 b2600i auto trans. I was bled all the old fluids out with preston dot 3 brake fluids. My issue was no pressure at all. I thought it was some airs in the line but it's not. I bled a whole big bottle of fluids. I have my wife pump to bleed and fluids are flows fine. But then when start engine, all the pressure gone and pedal become loose. Can some one please help with any advice would greatly appreciated!

Again, when pump up with engine off, it has a little pressure. As soon as the engine started, all pressure are gone. Pedal loose no pressure at all. This is wierd. I checked all around, no leaks.

Check the brake booster. It should hold vacuum. There is a check valve in the hose going to it.

The booster is working fine. It holds vaccum in there as it should.

Does it matter if i use Dot 3 fluids? What is the different between dot3 and dot4? Thanks.

Sounds like a brake master internal failure to me. DOT 3 and DOT 4 fluids can be mixed. DON'T mix synthetic and non-synthetic.

When you bled the brakes, did you hold the pedal down until the bleed valve was tightened BEFORE releasing the pedal? If not, everytime the pedal was released, air was sucked into the open port you were bleeding.

Also make sure you adjust the rear brakes manually before you bleed the system. Turn the adjusters until there is a very slight drag.

Dan; did you mean i would have to take off the wheel to adjust inside the wheel hub? Thanks

Yes, i hold the padle and tighten the bolt before release. I have done this type of bleeding for all of my cars. This time something strainge happen to me without showing any signs of defected part. I will try to adjust the rear drum today if that's the case.

No there is a small adjuster slot in the back of the rear brake backer plate. Use a screw driver to make the adjustments. I forget which way you need to move them but you'll be able to figure it out.

If the brake adjuster have not been turned in years, you may have to pull the drums to free them up. At the same time you can see whether to push up or pull down on the brake adjuster tool (sometimes, some vehicles, you CAN use a screwdriver) to spread the adjuster. Also see if the shoes need replacing before you go metal (shoe or shoe rivet) on drum metal.