Worcester Heatslave II 25/32 oil pump bleed screw leaking oil

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27 Feb 2026
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Hey there,

I have in the past bled the oil pump using the hex screw shown in the attached photo. However today (oil ran out from main tank and I needed to bleed air out), it seems to be leaking oil even when firmly tightened back in with the allen key.

I'm concerned if I leave the boiler on and close everything back up its going to keep leaking oil out the screw. Is there a replacement part for this screw in particular? I haven't tried taking the entire screw all the way out, but if possible, I can isolate the green oil pipe also seen in the photo as a bit further up there is a lever to isolate it.
 

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That doesn't look to be an original part .
Difficult to know what going on .
Id Just change it look for Riello pressure gauge extension they come with a new O ring.
 
The correct Riello screwis tapered into the extension. The washer that is now being held by it is a codge someone has fitted up. See Exedon post above.
 
Thanks both. So you're saying this looks like an extension part fitted onto the oil pump, and I should be able to remove it with a spanner (the whole length is hexagonal so I guess made for a shifting spanner to unscrew the entire part)?

Then in it's place I could fit a Riello pressure guage extension? Those seem to be made for vacuum pump attachment, would I still be able to bleed the oil pump if air gets into the system easily?
 

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