how do i get 3 cold raiators to heat up, when all the others are hot?

1/ Are all three Rad's in series or parallel ? If series any one valve being closed will stop all 3 !
2/ Can you isolate the temp. control valves ? If so strip the top ( bellows ? ) portion, slowly return water to line while checking for leakage and then open the control valve manually; press down or pull up as appropriate. This will tell you if the blockage is truly at the control valve or elswhere.
3/ If it's the valve most manufacturers will supply repair kits; beats taking the valve body out of the line and fixing subsequent leaks.

GMR
November 2007

To add to a previous answer, here's a tip on how to tap on a plumbing fixture with less chance of bending or breaking the fitting. Use two hammers. Hold one against the fitting on one side, and rap on the other side with the other hammer. The shock wave passes through the fitting and makes the other hammer move, sort of like those desk toys with the five steel balls.

Tom Gloger
November 2007

lightly tap the valve with a hammer--if still not working take of top lightly tap spindle-dont hit too hard

wp
November 2007