Rad Valve Question

[WaterTight]

So my mum had a rad valve body from a TRV, with no TRV cap.

The store told her she'd need to know the make of the TRV before getting a replacement cap, which she did not know as it's not written on the body.

Next time I come round she'd improvised by taking the cap off a normal rad valve and putting it onto the TRV body and had turned the rad off.

Incidentally, the rad valve she borrowed the non-TRV cap off also has a TRV body underneath.

Questions:

1) Given how it seems she has managed to turn them off with this cap is it the case that a normal rad valve cap can be used to turn a TRV valve on or off?

2) Might this have damaged the pin or the valve body or created the risk of a leak if the cap if the cap should be taken off again?

3) After turning off the two rads in the house extension by this method and then turning the heating on to check, they successfully didn't get hot.
But the radiator in the room next to the airing cupboard (where the HWSC and boiler are) started making noises for the first time ever. The noises sounded like it was either filling up or draining down. But that's a guess. It also felt hotter at the bottom of that rad so it now needs bleeding. Would this have happened because of the two rads in the extension being turned off for the first time in years? And if so, why and what's it all mean?

Muchos gracias

 

[Puddle]

Well vent radiator next to airing cupboard to release air, propably always had air in it but now you have turned off two rads the increased pump presure as made rad sound noisy
The thermostatic valves cap be turned open and closed manually as you describe no problem, you are just doing manually what the valve head would do automatically
However you can only have open or shut the valve head allows the flow to be restricted allowing radiator to keep area around at desired temp; it does this by means of a small wax cartridge in the head that expands as air temp rises and contracts as air cools
You should be able to get another thermostatic head for valve, they all unscrew, so take one off another radiator and take to a plumber’s merchant and they should be able to match up, you do no have to have same make of valve as several match up