Looks like your valve may not have the separate smaller packing nut that is in the one I posted. It looks like yours may have the packing contained under the larger nut.

I've attached a cutaway valve picture to give you a better idea.

I've never had a lot of luck with those because sometimes they are really tight (but still leaking) and getting them broke loose while trying to hold the rest of the valve tweaks something else. Do you have the new washer hose tight ? Did you use pliers to tighten or is it only hand tight ? Also did you use a new rubber washer on this end of the hose ? Sometimes the old ones get compressed or get a groove in them and they will not tighten down and seal especially since this is on the hot side. These should be the same sort of rubber washers found on garden hoses and attachments. Sometimes even a little turn with a pair of pliers to snug the hose up will prevent or stop the leak.

Can you  definitely determine if the water is coming out of the valve cap (green arrow below) or squirting up out of the hose connection and making it look like it is coming out of the valve cap (red arrow below)

Even if the valve is faulty it looks like a simple job to replace/correct. At least it is all out in the open and not buried inside the wall or in a shut off box where you can't get to anything.

Good luck and post back your fix.

(packing.jpg)

(Water spigot 2.jpg)

packing.jpg (14KB - 71 downloads)

Water spigot 2.jpg (31KB - 71 downloads)