You can probably dissolve most of that buildup from the coolant by letting that valve soak in vinegar.

You can use a needle, small drill bit, or a thin nail to clean out the passageway. Just try not to bottom where it seats when you tighten that valve. Also, if you have that much corrosion in the coolant system, you may want to run some of the radiator flush to dissolve the buildup likely throughout the system.

 

Thanks PaHonda... I haven't worked on the car for a week now. Gonna try your suggestions out and see what will happen. I'll let you guys know what the result is. Just got a camera so I'm going to take picks and stuff of some of the things I'm working on.