I have an oil boiler and one of my radiators is making an annoying noise, almost like a vibrating noise. Thinking it was trapped air I tried bleeding it but no air came out, just water straight away. I have the thermostatic valve set to maximum (setting no.5) and if I reduce the valve just half a notch (to 4.5) the noise disappears but will re-appear again a couple of hours later. I have also noticed that when I do reduce the thermo valve, even just down to 4.5 or 4, the amount of heat is drastically reduced to the point that the rad is barely luke warm. Could it be the thermostatic valve at fault?
I am not a plumber, so limited to my own houses for experience, old TRV heads seem to be larger thread to new ones, M30 x 1.5 mm seems to be the standard now, replacement heads also come with adaptors for RA, RAV, and RAVL heads what ever they are, and with a M30 x 1.5 mm thread it is easy to swap heads, I have swapped most of mine for electronic programmable heads, I have 3 makes, eQ-3 with blue tooth cost me £15 each in 2019 and can't work out why anyone would use mechanical types at that price, but brexit has resulted in price going up, there is also the Terrier i30 which is very similar, down side it will only connect to one phone, and you need to be close.
On the plus side you can manually adjust, no need for a computer or phone, the Energenie were the first I used, far more expensive but connect to you wireless LAN so you can monitor and adjust anywhere in the world but a £78 a pair plus cost of hub, more expensive, and no option to manually adjust.
The last one is Kasa (TP-Link) £35 each and kit with hub £42 and the hub with a button doubles as a door bell, these like the eQ-3 can be manually set, but like the Energenie can be controlled anywhere you have internet.
Then you go to the types which connect to a wall thermostat so they can also fire up the boiler, Hive, EvoHome, Wiser etc, the Wiser claims to work out how long it takes to heat a room so you set time and temperature you want and it works out when to switch on.
I think the whole idea of a TRV with *123456 is daft, I want degs C so I can set each room as required. So the mechanical heads seem daft.
It seems likely noise is related to the head, but years ago the TRV had to be fitted correct way around, and could hammer if fitted wrong, so step one see if there is an arrow on the valve, if so is it in the right direction, I find the TRV works better on the supply side, it gets the heat quicker for it to adjust.
Step two check size of thread, M30 easy, adaptors are made for M28 but the larger ones seen nothing.
Check the setting of by-pass valve and lock shield valve, and pump speed if you can adjust, pumps seem to auto adjust today.
If you can fit an electronic head that seems a good idea, but first swap with a head from another room, do easy things first. If the thread is large likely a old TRV so may need changing, but even if changed using an electronic head seems the right move anyway.
But you need to sit back and decide your ideas for the future, if you are going to fit new TRV and head you don't want to have to repeat again in the future.
The gas modulating boiler works very well with TRV heads and one can program when each room is heated, the oil boiler does not work quite as well, it does work, but turning a boiler on/off does not work as well as turning a boiler up/down.
I note like me you have oil, mine the pump is on the return, not found a by-pass valve, good luck.