Adk46

What are these two tubes on either side of the air cleaner that are blanked off with light blue caps? On an '87 S4 auto. Thick-walled tubing, like for hydraulics. Just curious.

ammonman

IIRC these are sample ports for emissions testing.

Mike

Rob Edwards

Curt- These are test ports for exhaust gas (CO) measurements. You will never need nor use them.

From the 1987 Service Info Tech guide, page 1-14:

Adk46

Ok, thanks. Upstream of the cats. No good for 007-style smoke generators, then.

martinss

The base of these tubes where they bolt to the exhaust pipes can rust thru causing a small exhaust leak. The top of the tube that you show can look fine. People variously replace the tube with a ball bearing, bolt or some such under the retaining nut to plug the hole under the retaining nut.