Frank3

I was doing the lawn the other night and needed to move the Impala so I could get in and mow a tight spot. I started the Impala up and immediately heard a loud sputtering-type noise you commonly hear with exhaust leaks. Initially I thought it may be a bad doughnut but on closer examination (not much room to look at it) it appears that the downpipe/catalytic convertor assembly has a cracked pipe right where the pipe connects to the flange at the head on the LH side of the motor. Once it warms up in 2-3 minutes the extra noise is gone, but you can still smell the "pre-catalytic" exhaust fumes under the hood. I called the dealer and told them about it. They want me to drop down with it so they can see it can order the right parts. I never expected this as 30,000 miles.

Frank3

I had my wife take the Impala in to get repaired yesterday. It took a while for the parts to get in at the dealer. They replaced the LH catalytic, associated gaskets and all the nuts and bolts. It looks like they re-used the O2 sensors. All covered under warranty as the catalytic structurally failed in a manner that was non-serviceable except by replacement. No sputtering exhaust sound when it is started cold.

Nathan Buerk

2017 impala 3.6 liter. I have the same problem now. It occurred at 35,000 miles. Flex pipe seems to be cracked.

Frank3

Hi Nathan, thanks for the reply. So yours cracked after the cat?