On Sat, 12 Nov 2011 15:47:00 -0800 (PST) Weatherlawyer 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.

Those of us of a certain age will remember the Jennings book where a
potato rammed up the exhaust has the same effect.

--
Tony Bryer, Greentram: 'Software to build on',
Melbourne, Australia www.greentram.com