Banging noise in radiator

[Alex60]

Hi guys, I would appreciate an advice - I changed a thermo valve on a radiator a couple of weeks ago, and it was working fine. But the customer called me a week later and said that the radiator starting making loud banging or screeching noises every time about an hour after the central heating was switched off at night. When I came to see it yesterday the heating was off, so I could not see or hear anything, and could not do anything. The customer said he checked it on internet and recons it must be due the new valve. I said I would consult the forum and get back to him. Your help be much appreciated.

 

[SimonG]

Is the new valve bi-directional? Fitted at wrong end?

System could be full of crap and the new valve could have smaller bore and trapped some crap?

 

[SimonG]

Is the new valve bi-directional? Fitted at wrong end?

System could be full of crap and the new valve could have smaller bore and trapped some crap?

 

[Last Plumber]

As above but out of interest, what type of system and what boiler?
Is there an auto bypass fitted?

 

[Gasmk1]

an hour after its switche doff the pump wouldnt carry on running for that long if you mean turned on, tll him to wait till noise happens then turn the new trv off if it stops the noise theen the valve is the problem