Removing combi boiler pump head?

[DrNibor]

I am trying to replace the pump head of my Myson Compact CP51. From all I can find on the web and the replacement instructions, all I have to do is remove the four corner screws and withdraw. However, at this point it will only come forward 10 mm or so. From the other pump I have I can't see what is stopping it from coming away. Any ideas appreciated.

 

[45yearsagasman]

Probably the impellor jamming against the pump body.If the pump body is cast then just give it some extra persuasion and it will come out.

 

[DrNibor]

Thanks, you were right. However, having removed the head, I have found that the castings are different. I've tried to remove the old casting, but the top nut is seized. Any suggestions?

 

[bengasman]

Buy the correct pump.

 

[DrNibor]

Yeah thanks for that, you were right though. Of course I didn't know I had the wrong pump when I bought it, I trusted the shop to give me what I asked for.

 

[Boilerman2]

Never trust a shop! they'll sell you anything!!

 

[DrNibor]

Yeah, well I gave him the potterton part number and he came back with a pump that looked just like mine. It was only when I split mine I realised that the impeller/castings were different and I wouldn't be able to do a straight swap of the heads.

 

[oilhead]

Hacksaw through the siezed nut, they cost a couple of quid to replace.