Saturday, November 28, 2009

Removal and Installation of the Catalytic Converter on a SAAB 9-5

I fouled the stock converter on my SAAB while trying to recover from a failed turbo. The car ran poorly, with a rough idle, stalling, surging, and there was a lack of power and decrease in fuel mileage. A stock replacement catalytic converter from SAAB was around $1500. A 3 inch downpipe and race cat from was less than $600. It arrived at my door less than 48 hours after I ordered it.

Removing the old converter was straightforward. I drove the car onto ramps, blocked the rear wheels, set the brake and disconnected the battery. I also disconnected the wiring harnesses for the two O2 sensors. These are located near the firewall, next to the throttle body and brake reservoir.

There is no need to remove the oxygen sensors until the entire downpipe is loose. Remove the heat shield and pipe connecting the diverter valve to the turbo's cobra.

There are three nuts / threaded studs that connect the turbo to the downpipe. Remove these, but keep the old downpipe supported on the threaded studs that remain. I had two nuts come loose and one threaded stud come loose. It really doesn't matter.

Under the car there is a metal bracket with a bolt or two that will need to be loosened and there are three nuts that need to be removed where the downpipe meets the resonator in the middle of the car. Once these are loose you can start wiggling the old downpipe and converter  until it is free and can be slid out from under the car.

Once the old pipes are loose you can remove the oxygen sensors. I used liquid wrench and an open adjustable wrench with a rubber mallet to get mine off. This would be a good time to replace the two O2 sensors, if necessary.

The sensors are then installed on the new downpipe and installation under the car is done in reverse. The metal bracket by the oil sump is no longer used with the race cat. The O2 sensors might need to be rerouted differently to reach the wiring harness, but that's no big deal. Use the threaded studs at the turbo and resonator as extra hands to adjust the pipe into place. Take your time and tighten the bolts completely once in place to close any exhaust leaks.

Here is the inside of the racing cat.

This project gives you an opportunity to check on the health of your turbo. Here is the inside of my turbo, one year after it was installed.

The project was simple and the results were immediate. The car needed a working converter. The upgrade to a 3 inch downpipe brings me closer to the ability to go from my current stage-1 to a stage-3, once I get the correct software from BSR, Aero cobra, and a larger cat back exhaust.

-P. Econmancer


  1. Hey! I was just wondering if I can reverse my stock diverter vavle for that awesome turbo noise :) i recently purchased my 9-5 and im loving it and now im looking everywhere for performance parts or anyways to give my car some extra horses for cheap because i dont have a job as i am a college student. Love all the stuff you have done to yours! i hope to get a complete exhaust system for mine someday. Thanks!

  2. Thanks! I'd like to get a performance exhaust, too. It's still all stock past the cat.
    The stock DV will have a hard time staying closed in the opposite position because of its design. The diaphragm on the stock DV will let air slip past and you'll get lower performance. But it won't hurt anything to flip it around during a weekend and see how the car reacts, give it a try some afternoon and be ready to put it back to normal. Experiment!

  3. When you took your old catalytic converter off, did you take a picture, and if so, was it visibly messed up? I think I am right where you were after a failed turbo. Thanks, and great site!

  4. The pipe bends in such a way that you can't see inside either of the old cats. What kind of symptoms is the car having and how many miles on your turbo?