myson apollo update

1 drained system over weekend flushed with mains water several time.
2 vented all rads pump.
3 added white powder ( after acid cleaner been in 4 days .)
4 water can be heard gushing around system seems to have good flow if not better than ever.
5 flow and return pipes only warm so are rads hence stats??.

question is apollo boiler cuts out still after 5 mins after lighting just wondering if stats loose there tolerance after boiler has overheated several times.
has had new pump 3 x gate valves flushed with mains water and chemical flush.
plumber is x bg engineer will not remove casing to check stats didnt keep corgi reg now retired,
thanks for your input and efforts especially chris r seems to know a lot about these boilers. thanks

Did you ever fix this problem?

I drained some water out from my water system and added X400 sludge remover. After refilling my boiler now only fires up for five minutes at a time in both the high and low setting. Ive had a friend around whos corgi registered and weve checked out the high and low over temp switches which are both OK and water is heating up and pumping fine in the five minutes it works. I just dont know why all of a sudden it cuts out.

I wondered if its the thermostat that is located at the back directly above the control panel box. It looks like it has three wires but will be a right pain to get back in if I remove it which is why I havent.

Anyone have any ideas? By the way the model is Myson Apollo 50/65B.


Update: I have now tried removing the brown wire from the pump over run stat and the pump doesnt run, so that stat is ok as the pump is runs when its supposed to. I don't know if there is anything else in the system apart from the hi/lo stats and the pump overrun stat.

cant be 100% if that modal has a limit stat but from what your saying sounds like it has.