Front disc metering valve on stock 71 F250

[Hungarian Hammer]

Hi all. I'm just getting started working on a stock 71 F250 Camper Special (6900 gvw). She runs and drives but I'm not satisfied with the brakes so I'm going conservative and overhauling the whole system. I've been on the hunt for parts and last week came upon a decent deal on an NOS metering valve. It came in and looked real nice and shiny but I found quite a bit of copper oxide in one of the ports and the bleeder button won't depress.

The shop manual is pretty clear to not try to disassemble or rebuild this little guy in any way, so my questions are:
1. How is this thing supposed to work? Does it need to have pressure or fluid in it, or should the button readily depress dry out of the box? I haven't found much in the way of details or cut sheets showing the inner workings.
2. If the seller doesn't take it back, is there any way to open this thing up without ruining it? I saw a little snap ring on the top but was worried the whole thing might fly apart if I mess with it.
3. Any non-NOS or non-junkyard options here with newer equipment retrofits?

Thanks in advance, will post some pictures of the truck soon!

[jp2005]

I would send it back, and get a new one.

[tqwrench]

I just rebuilt the brakes front and rear on my 69 F250 390 CS. I didn't screw with either the prop valve or metering valve and they work very well. I had to make a very hard stop recently and it performed quite well. That being said, I've never seen one fail. Only time I've ever heard of it was fluid contamination with the likes of power steering fluid or other petroleum based fluids. At that, they'll start bailing fluid from any external seal. My bleeder button is stuck too but again, I didn't mess with it because I was getting fluid out of the fronts and bled them without having to depress it. Granted, I did get a bad master cylinder during this process but that was easily remedied by an Autozone replacement, though I did have to "wash" some debris out of the reservoir (with brake fluid).

I recently found my brake warning lamp was cut out of the circuit with what looks like a dull knife, rewired it and found out why, it's stuck on all the time. That means I need to get to the prop valve and find out why. Hopefully it's something simple. FSM says to loosen the fitting at the last part of the system bled and operate the brake pedal to get it to go off. Haven't had time to mess with it yet.