sounds like air lock" how many taps have you on the sink , just one mixer tipe , or two taps , hot and cold? if its two taps, try run a small lenth of of garden hose , about 12ins long , from the cold tap , to the hot tap, , put one end of the hose into or over the the end of the cold tap , and the other end into or over the hot tap ,turn on the cold tap , make sure that you have hot tap open (ON) let the water from the cold run into the hot tap , to fill up the empty gap that the air lock has made in the hot water pipe, when the running water hits the airlock it will free it , and you should have it working again it might take 5min of running water to clear it , , if its a mixer put the plam of your hand up very tight to tap to cover it , and do the same as above" open the two taps, to backwash it ps you might need a teatowel for this one to keep the spray down , good luck
mick
April 2008