crazy potterton puma 80e

[jren]

I have a Potterton Puma 80e which is driving me crazy. It has a Myson Compact CP61 pump (not checked).
1st problem was losing pressure slightly - no leaks in house but floor underneath looked like had historical leak issue, but not sure about expansion pipe, kept filling via loop on regular basis- Hot water non existent while heating on unless run at a snails pace
2nd No heat to radiators at all now - pressure problem worse - filling daily sometimes twice - rise up to 3 bar then falls back down. Water now comes out scalding - heating kicks in for couple mins then goes out completely unless running hot water tap at same time. Heating only kicks in if the hot water tap is on. Hot water bubbling and steaming from boiler. But still not circulating
Today tried to fill up with loop - twisted pressure release valve - boiler vented - now is losing water as quickly sa I can get it in. Cannot keep checking outside pipe as is on upstairs neighbours wall unless they are in.
Have been advised new diverter valve?, new expansion vessel and new pump possibly??

Help

 

[bripl]

a proper service to include cleaning the combustion chamber/clean and adjust burners[if ness]replace any leaking parts aav s/r valve,check operation of e/v recharge if ness check operation of boiler with correct tools flow rates temp rise,burner pressure,standing/working at max.once this has been done you may be able to diagnose the problem without replacing half the boiler hope this helps

 

[DP]

Very good answer. Could not have put it better myself. Would appear to be a DIY or a cowboy job.