Central heating help

[bensnodiyexpert]

We have a closed central heating system with a Potterton Netaheat boiler, which has worked well for 14 years or so with the odd part being replaced, pumps etc.
This year it has become much worse & after 3/4 plumbers visits and the boiler has had a new PCB, & another board, a new circulating pump (circulating pump ltd CP53 Mison clone), motorized valve & automatic air vent. After all this the boiler still keeps cutting out & has to be reset.
Other symptoms include daily loss of pressure, some dripping from the overflow, circulating pump overworking & lots of air in the hot water system (the radiators have been vented) & I have tried to vent the pump, but this model has a strange bolt on it instead of a screw that most other models have.
In addition, the hot water was fine on its own during the summer (so I don't think its the boiler) until I drained the central heating system to change the air vent & add Fernox, now it seems to be worse that the heating & the boiler needs constant resetting & when the bolier has cut out, the pump continues to pump & over works, with lots of water noises (air?) in the system.
Any suggestions, tips greatly appreciated. Thanks

 

[Tindog]

Wow, there's a lot going on there!

Can't explain all of it, but if you have a pressure relief valve, the dripping overflow suggests that it might need to be replaced. That would also explain the pressure drop.

 

[bensnodiyexpert]

Thanks Tindog, I will look into that.

 

[Gees]

14 years is a long time.. a very long time.
You might think about a new boiler now.
Think of the efficiency of a new one