fellow engineers, advice on ecomax?

righty ho, vaillant ecomax firing whistling and extinguishing.

it blew a hole in the flexible re-enforced tubing on pipework to heat exchanger so boiler was off when i arrived. Replaced tubing re-filled vented everywhere possible but heat exchanger still sounds in distress. rising from about 20 deg to 80 deg in around 6 secs then turning off and waiting to re-fire on normal anti cycle time limit.

luke warm water if you're lucky and very little ch,

has anyone had similar problems with this boiler or heard any stories, im thinking blocked h/ex but they around £300 + so would have to be sure...

any help (in exchange for a handful of haribo and 50p) would be greatly appreciated.

cheers