Like a car engine turning but not starting...

[flood]

My boiler is having problems. After a while (a few hours of the heating being on), it will turn itself off. Then, almost instantly it will attempt to fire back up but will fail a few times before actually starting. But then it will turn itself off again!

This cycle repeats a few times until eventually it starts up and stays on.

When it is trying to start up again, there is a double clicking sound...[tick tick....tick tick....tick tick] <-- like that, before eventually firing back up again, albeit for a random period of time (a few seconds anywhere up to a few hours).

A couple of guys have been round and failed to diagnose the problem.
The 2nd guy (from British Gas) advised that the thermostat may need changing but he didnt sound convinced.

For info: During summer it was doing it just whilst the hot water was on.

One last thing, after the heating is on for a long time, there seems to be a build up of pressure which is then released through steam and lots of noise through U-bend vent pipe over the hot water tank in the loft.





Its a potterton kingfisher Mf.
There is a hot water tank upstairs which doesn't have a thermostat. Yes, it's a terribly old and awfully wasteful system.

 

[Blooflame]

I think you MAY have two probs. One: the pilot injector is blocked. Two: there's a blockage OR the pump is screwed up causing overheating. You have a gravity system, it's possible the non return valve is on the return pipe...anyway either way it could be this that is blocked and causing overheating

 

[stevefixitall]

this is the kingfisher mf with the pcb yeah, did the chap at bg check temp on flow/ return pipes. poss may be a blockage/dodgy pump could well be dodgy stat on boiler

 

[flood]

Yes, it has the PCB. I don't know what he checked, wasn't at home when he came around.

It does it a lot more often when only the HW is on. The pipes creek and after lot noises the vent pipe starts venting. After which, it all calms down again.

So I will change the following 3 parts:

1. Pilot injector
2. Stat
3. Pump

In any particular order or is this ok?