My boiler works better when it is cold than when it hot

[Albert]

I have problems with my boiler Main Eco Elite because it works better when the weather is cold than when the weather is hot. When it is cold my boiler every two or three weeks stop working, the message E119 appears and I need to re-pressurised it.

However when the weather is hot this happens every day about at noon when the temperature raises. Suddenly the boiler stops even if the pressure is still good and progressively the pressure goes down to near zero and the message E119 appears. When it is less hot like when it rains for example this happens less often about every two or three days

I found out that this could be due to a leak but I have seen none. Moreover I am wondering why it will leak more when the weather is hot than when it is cold?

I do not always use this boiler. I know I have to repair it by an engineer but because of the coronavirus crisis I would prefer to wait a little bit and in the meantime I would like to know if you have tips to help me about how to manage this problem so that my boiler stop less often to work

 

[oz-plumber]

It sound like the system is leaking through the pressure relief valve.
It could be due to expansion tank losing its charge or bladder perforated.

Just keep topping it up for the interim.
You will need a qualified person to look at it before too long

 

[Albert]

I would like to know in the meantime how to use the thermostat, the timer, the control about the radiator and this about the hot water of my boiler so that this problem is decreased