On Nov 12, 8:53*pm, Steve Walker -
family.me.uk wrote:

Polyurethane foam?

That's the one.

Squirt some water into the exhaust then cut the top and bottom off a
tube of expanding foam adhesive and ram it in. You will need five
minutes or so for the effect to initiate. Half an hour would be best.
Repeat as necessary.

Wear gloves of course.