How to replace a Gen 3 catalytic converter without draining the exhaust preheater coolant...

After three years of research and study, my husband, his friend and I, being veteran aerospace engineers and technicians, have developed a simple method for installing a new after-market catalytic converter on a Generation 3 Prius, including a Prius v and a Prius c.

I. Cut off the old converter or the stub left from a stolen cat at the weld right at the entry end of the exhaust preheater.

2. Install the new cat and measure the distance between the end of the new cat and the entry point of the exhaust preheater. Mark off a one inch gap on the new cat so there is a one inch gap between the preheater and the new cat. This is where the end of the cat needs to be cut off.

3. Weld on a one inch section of exhaust tubing of the same diameter as the exit tube diameter as the replacement cat. 2-1/4 inch is a usual diameter.

4. Connect the end of the new cat with a stainless steel exhaust butt joint clamp like this one sold on Amazon.

Exhaust Clamp,Butt Joint Band Clamp Sleeve Coupler Stainless Steel



Using this method, there is no need to disconnect either battery for welding, because the exhaust system is isolated by the rubber exhaust hangers. No coolant needs to be drained. And, only the catalytic converter needs to be removed.