Hi all.

The exhaust system on my daughter's 91 240 fell apart, so I picked up a new cat and exhaust system.

The three bolts holding the header flange to the cat flange were solid rust. While banging around, the cat, cat flange, AND header flange came off as one piece. The header pipe where the flange was mounted is clean (it even has a rib on it that presumably held the flange.)

Question: is there any such thing as a clamp-on replacement flange for the header pipe, or am I looking at replacing the header pipe, too?

Also, the 02 sensor would not come out of the cat, so I had to cut the wires. If I run w/o a sensor (my cat came with the plug), will I impact performance? This card does not need to pass emissions in MA...

Thanks!

On my '91 245 I got an inexpensive Universal Carsound cat and a cheap ($65) header pipe without a flange and had a shop weld the two together. I just drove there with the new header pipe I had installed, along with the back end already assembled in the back of the wagon. Whole thing cost me less than $200 total.

Sounds like the header pipe is on it's way out if the flange is gone, so you should get one anyway. The '91 shoild have a solid flange, not a spin-type

As for the O2 sensor, as others have said, you need it to make the car run right. You can compromize on exhaust parts to get by, but not on engine management parts.

I would not use a splice-in $40 sensor because they are very subject to fail due to the connection and how/who does the wiring (correctly), and it's worth it to get the OEM Bosch sensor for $115 at Autozone and just plug it in. There's also a very good chance your old sensor wiring is toast after an old exhaust like that
burned it up. Also, the '91 has the O2 sensor in the cat, so the cable is longer than other year 240's, best to get the one that fits.

There are two kinds of flanges on the header pipe / cat converter connection. One is welded on both the header and cat. One is called a spin flange, it spins freely on both pipes. You need to match the type of flange with what is being mated to your header.
Dan

Flange on the header pipe is necessary, and may be a junkyard part. Find one or make usable the one you have, then get a someone to weld it to the header pipe. Ask a Meineke Muffler Shop or custom exhaust shop.

Pulling the the header pipe is another rusted bolt problem, best to soak the nuts with P'Blaster overnight. Get a new gasket, too.

The O2 sensor signal tells the engine control computer how much fuel to use. Without that signal there will be either too much fuel (poor mileage and premature cat failure) or too little (tends to cause burnt valves).

Not to mention the emissions increase.

Locate a shop, take along the fallen-off flange, and be certain they can do the job. Driving to the shop will be noisy and maybe smoky, so choose what time of day for the trip. Prepare to leave the car more than one day.

Be sure the shop gets the orientation of the flange right. If you opt for a new header pipe, (my recommendation) the orientation problem is moot.

Good Luck,

Bob

:>)

Hello,


If you can’t spell the word ¨Car¨ correctly, you might consider correcting your emission control problem. Note that it would not be you who must drive the vehicle with a defective fuel system, but your daughter.

The long term operation of an engine without the mixture feedback system could result in permanent damage to other parts.

An O2 sensor at Autozone is about $40. At that price, you can expect to lose more in lost fuel investment then the cost of the part, every year.


Goatman