3.5mm silicon vacuum hose

[Goran]

I thought some of my vac hoses needed replacing, so I bought this stuff from Baker in the States. It turns out my hoses were ok, although the rubber has started to go soft in places where it touches hot aluminium parts of the engine, its going to go soon.

The Baker stuff is really good, very thick walls, bad pic but its over 8mm diameter overall, and inside is 3.5mm same as stock. No way is this stuff going to collapse like some of the cheap silicon hosing out there. I'll be replacing mine soon.

Audi hose is £12 per metre for standard, or £18 per metre for reinforced diesel hose, but both are still rubber.

http://www.bakerprecision.com/hosetech.htm

[Goran]

Audi gave me a 1m piece of the diesel hose for free, so I replaced one of the old hoses and did a post mortem on it, split it lengthways. The part where it started to decay is discoloured with a faint white stain (to the right). It was still holding vacuum though and not completely decayed yet.
The dust is actually produced by the fabric braiding, it decays first and falls apart when you touch it leading you to think its the rubber underneath thats falling apart in your hands, but its usually just the fabric, if you still have vacuum (test by disconnecting one hose, listen for the escaping air) the hoses are still ok.