can rad bleeder valves go screwy?

[525i winter driver]

i was trying to bleed my cooling system today and a lot of really weird stuff happened. basically my question (for now, heh) is can my bleeder valve be faulty?

i couldn't even get past step1... fill expansion tank until coolant comes out of bleeder valve... well i was parked uphill (cold) filled the expansion tank all the way to the top with the bleeder wide open and still nothing was coming out. and when i try to bleed it with the engine temp normal (warm) it doesn't do anything, i can even take the screw out and nothing happens, just a few bubbles for a sec then absolutely nothing. if i squeeze the pipe fluid comes out... seems to be circulating ok i don't overheat but my temp needle has been reading around 12:02pm ever since i had the hg and water pump replaced. (this is why i was trying to bleed it) any ideas please?

[duckloads]

you will need to stick a fine wire in the bleeder hole (screw removed) to loosen corrosion.

Better yet, remove the housing and clean it up from the inside. If you have that much corrosion, be carefull not to break any bolts while taking them off.

[525i winter driver]

ok so i tried cleaning the bleeder valve just from the outside and it didn't change anything. before taking that apart i tightened two hose clamps and all of a sudden everything was much better and the bleeder valve worked as it is supposed to. so far my temp guage is bang on noon again... will need a top up and a couple of rides to be sure but i think i solved the problem... thanks duckloads for the suggestion!