Henry_b
Think outside, no box required.
Some Wynn's additive is inbound to the Clarke abode.
Will bung it in and report back on the "noisy when cold" status.
<£10 to give it a go. What's bad about that?
Don't run her around with that in the sump.
I believe you bung it in the sump and let it run for 15mins then drain.