Brake Bleeding Issues

[seanb02]

Hopefully somebody on here can tell me exactly where I am messing up. I had the brake lines off at the MC to remove a T-fitting that an old trailer brake controller was hooked to. To do that I simply bled out all 4 corners before removing the lines at the MC to prevent a mess under the hood, also figured it would be a good time for new brake fluid anyway.

Well, now I've had great success gravity bleeding the rear brakes, but I get absolutely nothing from the fronts, not even a drop. Still nothing when pulling a vacuum on the system at the caliper.

I realize this has something to do with the metering valve, but I see absolutely nothing on the thing that I can push in or pull out. I popped the rubber bulb off of the one side and don't see anything over there, popped the switch out of the top and don't see anything I can do in there.

At this point I am quite lost, maybe the metering valve is stuck and I need a new one. But its probably something quite simple I am missing?

Truck in question is a 1978 GMC C25, 454 engine. Any suggestions would be greatly appreciated!