Pressure increase on Glow worm Ultracom 30cxi

Hopefully someone can help. We’ve had the above boiler for about 8 trouble free years.

But now the pressure keeps creeping up. Engineer has been out and replaced a knackered heat exchanger which he thought was the culprit as well as a few other bits and a full service but still it creeps up.

He’s saying the only other thing it could be is the filling loop (but reckons it’s rare) which will be around another £400 and unfortunately no way to check.

Does anyone have any other ideas that could be checked before doing spending more money. It’s gaining about 1 bar of pressure over 24 hours. It get to around 2.4 / 2.5 and I drain some water out of it.

Coincidentally I tried the heating and not all the rads are getting hot. Not sure if that has any bearing on the issue?

Any suggestions or thoughts appreciated. Thanks in advance.

£400 for a built in filling loop! .no way is it that price .you could look up the price of the part online easily enough

£400 for a filling loop!? That's madness, they're about a tenth of that, and a Glow-worm fixed price repair is only about £200 with parts included. Sounds like you've got a proper cowboy there, chuck him and get someone else

Has he tried/ checked the expansion vessel?? That’d be the first thing to check...drain, pump up to 1bar, repressurise boiler then bleed all rads. Easy job for a heating engineer