[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

RE: EGT thermistor location

Sorry to bother you, but what is the sniff tube for?  I ask because
I found a thin tube going from my exhaust shortly after leaving
the engine (manifold?), straight up into the engine compartment and
then just sitting there capped with a rubber thing.  It had rusted and
broken off the exhaust and there seemed to be a slight exhaust leak
sound coming from the hole, so I plugged it up and everything has run
fine for several years that way.  I am now wondering if this tube is
the "sniff tube"!

Yes, that's the 'sniff tube'. I believe that it is used for verifying emissions compliance at the factory and
serves no other purpose once the car ships. Plugging/welding shut is a typical fix for leaky sniff tubes,
should cause you no problems. The way the sniff tube attaches to the exh is different on different models.
On some it attaches right to the exh pipe. On the ur-q it attaches to the flange on the downpipe that
bolts to the turbo exh outlet via a threaded adapter. I was successful this weekend in drilling the tapped
hole in the flange and retapping with 1/4" NPT for the adapter supplied with the VDO exh temp guage kit.
Was a snap once we found the 1/4" NPT tap and I think it was a 29/64ths" drill bit. NPTs are not
symmetrical so you do need to be careful with how deep you run the tap. Like 4-5 threads should be
left showing on the NPT tap when at the correct finishing depth. The seal is via the threads and not via
the more typical shoulder seal. Plummahs will know this!