cleaning valves

just wondering if anyones done it. ive got a 3/8 in mac valve that doesnt stop tank pressure from going to the tank and then wont let air out of the bag. im buying a new valve to replace it. but i want to take it apart and clean it and see if maybe thats the problem. ive had a problem here and there with 2 others but there working fine right now. just wondering if anyone has any tips on cleaning them and what i should clean them with. also does anybody know what the pressure rating on the mac valves are? any help is great. thankss