What's This Hose For ?
 

Take a look at the picture on the first link :

Vacuum control

See the Vacuum Pipe (part #6), and where it attaches to the rubber boot on the left. There's a recepticle nipple there for the hose, but just under that there is a much smaller nipple, almost small as a needle. See this link for a closer view :

Hot-film air mass meter BMW X5 E53, X5 4.4i (M62)

What is that smaller one for ? There is a tiny little hose coming off that and it laces it's way back to the rear of the engine somewhere. But I cannot find that little hose on any diagrams or part searches. Mine has actually broken off completely at the recepticle and I need to replace it but I have no idea what the hose is called, what it's for, where it goes or what it's part number is.

Any ideas ? This is all part of an investigation I'm undertaking into a faint but noticable hesitation pattern in the engine while driving.

Thanks !

If the nipple on the intake boot broke you just need to replace the boot. If the hose end itself is deteriorated and broke there should be a plastic junction a couple feet down the line under the hood you could replace it from/to.

I don't remember exactly which hose that is, but I think it has to do with the fuel ventilation system. Maybe it goes to #11 in this link?

RealOEM.com * BMW E53 X5 4.4i EXP.TANK/ACTIVATED CARBON CONTAINER

BUMP

I am having the exact same issue as the OP, That small nipple broke on mine, and the end of the hose is deteriorated. While I had the valve covers off, I couldn't even trace the hose then, so wherever the "junction" is, is pretty far down the line.

I'm also having a very slight surging and a little bit of a rough idle, I'd like to take this obvious vacuum leak out of the equation.

I'll order a new boot, and try to rig something up with the hose, but I'd like to know what that hose is for.