After patching the rotted connection between the downpipe and cat on my NA 940 multiple times with Quicksteel (great stuff, BTW!) it's finally time for a completely new exhaust system - the whole thing is starting to fall apart, and is noisy as hell. Got everything I need from Eeuroparts, including new cat, downpipe and O2 sensor. The main question is, should I install the O2 sensor in one of the ports on the downpipe this time, instead of the one on the cat? As it's set up right now, the sensor is plugged into the cat just after the connection to the downpipe - so as soon as this connection weakens it lets air in just before the sensor and makes the car run rich, which has happened numerous times preceding my patch jobs. I figure if I move the sensor back to before this connection, I might have a noisy exhaust if the connection weakens, but at least the mixture shouldn't deteriorate as it has before.

Does anyone know if there could be a downside to doing this?

Thanks!

Here's one you will love. I had the same issue and on a lark I called the local Stealership to see what they would do...they make a "split flanges"!!!
I just used my trusty angle grinder to carefully saw off what little remained of the rusted old clamp then you can install the split flanges without removing anything else. F'n NEAT! Here's a picture of the old flange and the split flanges. Downside...25$! Upside....dont need to pull downpipe!

Dear mmal231294,

May this find you well. This is a great idea!! It should be added to the FAQs.

What is the Volvo Part number? Anyone, who needs one of these will be ever in your debt!!!!

Yours faithfully,

Spook

Hi Spook
Good to hear from you. The part# is 8551977 I believe. Pretty bleapin slick part I must say! I was all but resigned to removing and replacing the whole exhaust before I found it. As an aside the flanges do not come with the 3 nuts and bolts which are used to connect two flanges together, only the 2 nuts and bolts that hold the two pieces of each individual flange together. I had to run to Home Cheapo for those.
Thanks
Matt

Should take forever to rust away :-)


--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Neat! Its a 4 layer metal laminate composition as opposed to Volvo's cast iron.
I'll bet it was a bit less expensive than the OEM?

NAPA # 732-1137 Flange $6.99 each in 9/07
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Wow, those split flanges are a great idea! If I didn't need to replace the resonator and axle pipe too, I'd totally go for that. At some point, someone put a cheap, badly welded exhaust on the car (cat pipe is welded to resonator pipe) so I figured go whole hog and do the cat and downpipe too - the car has never passed emissions without a lot of 'help' from my friends at the local garage!

Will definitely do this next time, though - thanks for the tip!

no install it where it is supposed to be.

you have the spin flange on the cat and header pipe. if you are concerned about its seal and longevity, saw off the flared lip on each and slide a sleeve over both ends and use normal muffler clamps. the seal will be better and last longer.