Indirect cylinder

[Quiz]

Still check above .also could be blockage at pipework tee were hot water return joins heating return if near boiler

Did that, also took connections off the coil, both sides, and hoovered out with wet n dry all open ends.

Re-filled and before too long, same old whooooshing sound and boiling water into F&E.
I am now thinking it could be an inefficient pump, after all, that debri had to go through the pump to sit on the 2 port valve???
If I turn the boiler stat right down, it does not happen. But then the water and rads do not get hot enough.

 

[Puddle]

Well do not think is pump,as you say system works ok when heating is on and problem only when hot water on by itself,so does point to a restriction somewere on hot water circuit
This time of year does not matter if heating on,so if you can not find restriction, would put chemical cleaner in system and run round heating and hot water curcuit for a few days then try through hot water only see if any improvement and go fron there
Take it you have checked pull side of pump and valve to make sure not blocked/restricted

 

[Quiz]

That sounds good advice, pump only 5 years old. It is a little noisy when hot though.
I might do both,ie. flush with chemical for a few days and then put a new pump in when I flush the chemical out.

 

[Quiz]

Flushing /Cleaning fluid has been in for 3 days now. Still noisy when water only.
Someone suggested I put in a thermo relief valve, after the pump but before the 2 port and then stab back in before the T in point to the return to the boiler.
Will this help?