Xantia Lhm pump leak

[CitroJim]

A normal O ring should do duty here but it must be proved to be LHM-proof. I don't believe it needs to be of square-section to be effective. It does, however need to be thicker than the width of the square section one shown in the photo above. It'll need to be thick enough to 'squish down' a little when the pump is reassembled.

Prove the O ring will not suffer on contact with LHM by soaking it in a bowl of LHM for at least a week.