linea 24 ,braided pipes seem to be pulsating?

boiler gradually got noisey,found valve at top ,[expansion valve was leakin air,was serviced recently and possibly the tyre valve had jammed down, re pressurized to 15psi,but still pulsating.cutting off hotwater and ch and temp gauge shoots up to 80 odd degrees..is it possible braided hose choked or is it more likley the heat exchanger choked???