A weld for the catalytic converter mounting bracket and heat shield can fail. Rattling noise will be heard from the bottom/rear of the engine compartment.Google+
Car Problem Reports
Saab 900 Rattling Noise from Catalytic Converter Bracket and Heat Shield
Saab 900 Problem
Exhaust & Emissions Affected: 2.3L 4 Cylinder
Average Mileage: 162,333 mi (132,000 mi - 200,000 mi)
Visitor, 1997 Saab 900, 155,000 mi
Loud rattling that can be heard while driving right above catalytic converters!
Visitor, 1992 Saab 900, 200,000 mi
when depressing the clutch to shift, the heat shield rattles . The one ontop of the Cat Conv. I'm planning on cutting it off with a pair of metal shears. This will avoid any rusted hardware and removing the Cat. Conv. I've already cut some rusted pieces from the top where water builds up.
The heat shield appears to be connected with 2 bolts that run throuth the floor board. This would require alot of interior dismanteling.