Stuck! Removing a Seized Aluminum Valve Stem Cap. 

Happened to me also, used a dremal to get mine of also. I bought some aluminum lined with plastic to replace my aluminum ones.

Learned this the hard way unfortunately 😢

What a pain! Thanks for the heads up.

if you put some heat on it from a lighter or small cigar torch for about 30 seconds it'll screw right off.

Never had to do this , 3years old still come over as if they were new

It is very likely all the heat by friction made the metal expand and that's how you were able to remove the cap. A lighter may have done the same trick

Put some copper grease on them before you put them on !!