Central heating radiator whistle /hiss and smell.?

Whistling means steam if you have a hot water boiler then its over firing and that's bad and you need to turn it off and call a tech. If you have a steam boiler you shouldn't be adjusting anything on the boiler unless your trained or you are looking to relocate your house. To many people try to work on their heating systems not realizing they are risking their life to save a few dollars.