Thanks all.
There is a little more history.
Been at my house 2 years. None of the Rads had TVR's. These were all fitted. The Rads have never all heated up as well as what I though they should. When the TVR's fitted each rad was disconnected and flushed outside. The heating was ok, but not perfect, I think there's lots of reasons for this.
I noticed this year when I put the heating on one of the rads was weeping slightly. I tightened the nut, it nearly went so the next day a little more, but the nut cracked. I had to drain the system, remove the nut and washer (absolute pain) all sorted now, but some rads get hot some don't as such I looked at options.
I first looked at the pump, it was noisy so not sure if that was usual, but to be honest the new pump is so quiet it was worth replacing. It had a dial 1,2 and 3. I t was set on 2, I changed to 3 (I fiddled switching between the levels too much) then the dial simply span, I broke it. I took the controller (black box) off the side of the wilo 50 gold and there was brittle plastic, so it wasnt looking good inside. Also before this I unscrewed the little nut on the pump and it was spinning but water was leaking out of it - youtube videos suggested that shouldnt happen. hence swapped the pump.
It has 1,23 levels (like the old) and variable, which I'm lead to believe shouldn't be used with TVR's?]
Anyway, it was on on setting 1 but this morning I heard water again. I turned it down further and it stopped, just seems strange that water keeps coming out of the overflow extension in the loft with heat.
The water is clean, but feel I may drain again. I do have the chemicals, but don't want to add until I know I've got it sorted.
I will have another look at balancing the RADS, I watched this guy
https://www.google.co.uk/search?q=b...5.3552j1j7&sourceid=chrome&ie=UTF-8#kpvalbx=1
I haven't touched the valve that comes out of the tank.
Another thought, could this issue be caused by a broken coil in the tank?
Also when installing the new wilo pump, looking at it fresh out of the box with the flow arrow pointing down the controller unit was upside down, so the default setup is to have the flow arrow pointing up? The instructions suggest you can rotate the controller, so I did (I hope that hasnt caused an issue) and as I have said I made sure the flow arrow matched the old pump, which is pointing down.
Im thinking, flush the system out. fill up, remove airlocks and balance correctly (any helpful suggestions) and test.