Cast iron hot water radiator valve leaking around stem

[K Frame]

The radiators are about 100 years old. The one in the bath is slowly weeping water around the stem.

I'm going to try to tighten the packing nut to see if that cures the leak. But if it doesn't, do I have to drain the radiator down to repack the stem, or can I simply turn the valve to fully closed, loosen the packing nut, wind in new packing, and replace the nut?

[KD5NRH]

The radiators are about 100 years old. The one in the bath is slowly weeping water around the stem.

I'm going to try to tighten the packing nut to see if that cures the leak. But if it doesn't, do I have to drain the radiator down to repack the stem, or can I simply turn the valve to fully closed, loosen the packing nut, wind in new packing, and replace the nut?

I'd try a little teflon tape on the threads before replacing the packing, but about 85% of the time, a quick crank on the packing nut will work three or four times for several months to a year each before you actually have to replace packing.

[K Frame]

It's not leaking around the threads so tape there would do nothing.

[KD5NRH]

It's not leaking around the threads so tape there would do nothing.

Enough tape will always fix a leak.  Enough may just be more than you're willing to use.  Three rolls of teflon tape backed up by two of silicone tape and a roll of 6" gaffer tape should do it.

[K Frame]

Tightening the packing nut has stopped the leak.

Pretty obvious it was leaking for quite some time. I need to check the other 15 radiators in the house for the same issue...

[never_retreat]

Good thing, those old valves can be a bitch to get off.
Last couple I did required a 3 foot pipe wrench for a 11/2" valve.

[K Frame]

I've had to use a strap wrench to free some of them up so I could adjust the heat, but they've all loosened up.