Worcester Heatslave squealing on startup

[Avocet]

I'm just wondering if anyone could give me any pointers on this please? It's a Worcester Heatslave, 20 years old. On startup, as soon as the fan / pump assembly starts running, there's a sort of "whirring / squealing / whistling / warbling" sound. To me, it sounds just like a "dry" bearing. The fan and the motor that drives it are original. The oil pump (driven off the back of the motor shaft) is a Danfoss replacement, a couple of years old. If I take the oil pump off and turn the motor shaft by hand, it feels fine. No tight spots or roughness at all. The oil pump shaft feels quite tight to turn by hand, but I'm not sure what it is supposed to feel like. After the system has been running for a few minutes, the noise is reduced but still present.

Any thoughts?

 

[Burnerman]

The motor bearings do get a hard time, due to the heat etc.
They are 6202zz bearings and dead easy to replace.....involves splitting the motor, obviously! I guess it's worth sorting that first.
Next, try slackening the 3 pump securing screws (Allen, as a rule) just to see if things change. I would have thought that the pump is a bit young to have issues, but some folks reckon they aren't as good as they once were.
John

 

[Avocet]

Ta John. I was wondering about the pump. The noise shut up for a few days after I disconnected and re-connected it from the motor shaft, so I did have my suspicions! I'll try slackening off the cap head screws.

 

[Burnerman]

Just for interest, www.hwos.co.uk do the BFP41L3 pump for £37.90 vat extra......free catalogue too!
John

 

[Avocet]

Ta John. I might just need that! I tried the cap head screws and the noise definitely alters when I touch them, but doesn't really go away. Might have to live with it for a while though (see my other post on washing machines) - never rains, it pours!