main 28 he -overheating

[SafeGasInstall]

hi all,

did a water storage tank replacement today,after job done lady complaint rads not geting hot!it s a system boile Main28he boiler ground floor cylinder right above ,had a look i thought tree port valve has had its time ,as it did look melted overheated or something.changed it over still the same,boiler fires up overheat it self and looks up.then turn of 1 floor rads ,and run just downstairs did get the first and second worm,then turn off down stairs and run up stairs only same just first and second worm as boiler keep over heating.next i did is turned of all rads and put my house on the drain and start filling up and draining to over come any air look .boiler still looked up even i was introducing cold water !then i had a look on the pump 15/60 scolding hot !when changed the tree port valve noticed pipe work nice and clean ,so sign ther could not be blockage ,had my magnet out on the pipe work round the return pipe to boiler did not pick up anything!then i thought is the pump as it could not be the heat exchanger as i thought , ordered new pump going back on Friday!

any suggestion will be helpful !!!

oh yes did run it on hot water no joy the same, bled coil on the flow!
no sign of change so i think pump must be naked!

 

[aggis]

Sounds like the pump, but is there a filter in the return connection if same as Baxi [ remove cap on isso valve & pull out tubular filter with snipenose pliers.] could be blocked

 

[Billy Bob Bob]

is this the same boiler all beit a system version of a baxi 105 he?