converting to sealed system?

Would it be advisable to convert my heating system to a sealed type? The reason I ask is my boiler often makes a kettleing noise. Ive tried the usual ideas - flushing, silencing treatments but after a while it becomes noisy again.
The boiler is an Ideal Elan RS balanced flue unit which I installed about 23 years ago. My main concern is the possibility of leaks if I pressurise the system.
Please dont advise me to fit one of these new condensing combi pieces of junk which will last at best 7 or 8 years & require ££££ worth of parts within that time such as PCB's, fans, valves, pumps etc. My old boiler may not be most efficient but there is very little to go wrong, in fact in 20+years Ive only had to replace the gas valve ( £15 new from Ebay!) the thermocouple twice ( £5 - B&Q) & a thermostat (£7 - Ebay) - beat that for reliability! :lol: