I'm trying to source Silicone ducting over here.
http://pages.ebay.com/link/?nav=item.view&id=170708376186&alt=web
Comes in all the sizes you need.
60mm is demister tube.
70mm is from heater boxes.
80mm is dumping out the side.

Harley

I agree that for the most part, Citroen indeed knew best, but i find that the standard heater tubes are a massive pain in the ass to fit, are a real fire hazard being cardboard and so close to the exhaust and for one of the tubes my handbrake rubs it on the bottom and the heater control rubs on the top, causing them to wear out very quickly and making the heater controls difficult to move.

All of the above combined are enough to make me at least investigate alternatives that didn't exist when the 2cv was created.

I just fitted the neoprene hoses as above, along with new non rattly heat exchangers. Christ on a bike, what a frigging racket. It's like driving along in a tumble dryer full of spanners.

I shall be coming up with a solution in haste!

It's bizarre, mines never been quieter! With the demister open it's noisy, but how often do you have it on apart from in winter? and it clears in a couple of minutes!

Just turn your stereo up

Lol

It was so bad, I removed the hoses from the heat exchangers for the journey home!

is your dump/cabin flap working correctly and actually isolating the heater tubes effectively?

cardboard tubes with an inch or so of foam to kill the noise?

( paint them with one of the excellent clear acrylic varnishes to make them last longer than 30 odd yrs)

Yup, all working perfectly.

Could be

The foam inside usually breaks up before the outside deteriorates, then you end up with a cab full of 'crumbs'.

Or worse some bits in the eyes whilst driving.

That's what happened to the tubes on my Acad, looked fine on the outside.