two radiators do not get hot all the way

I was wondering if someone could help me out there. I have vapor system powered by a oil burner. It is a two family home. In the second floor apartment the bathroom cast iron fin radiator only get hot on the top of the radiator. The rest of the radiator is cold. I tried changing the vent valve's, but that didnot work. The other rad's in the apartment are all piping hot; however two radiators have the gorton equalizing valve(d) and 2 radiators have the varivalve qucik vent valve. Does it matter that the are two types of valves on the rad's? One of the rad's doesnot even have a vent valve. Should I add one? The radiator is very hot, but by not having the vent valve, is this causing the system to work much harder to build up the pressure to bring the steam into the radiator. Also, Should the lever on the varivalve quick vent be in the open closed or middle position?



On the first floor I have cast iron baseboard one of the radiators only get hot half way. Does this rad need to be pitched? I replaced the quick vent valve last year, but I still have the same problem. The rest of the radiators get hot from end to end.



How do I know if my system is operating efficently? I also notice in the morning there is a lot of knocking in the pipes after about twenty minutes of the system running. Please advise.