A Catalytic Converter Repair

I ACTUALLY TRIED this GM catalytic converter repair as a last resort, and it worked well. So I hope at least a few of the readers will find it useful.

A friend of mine, who owns an early 1990s Oldsmobile Cutlass Calais, showed up at my garage recently complaining of an obnoxious exhaust leak.

Upon inspection, I discovered that the catalytic converter was the culprit. It seems that GM built these units with some sort of press-fitted plug in them, and it had come loose (presumably from age and some minor corrosion).

I took a good look at the converter from front to back, and it was pretty solid aside from the one plug having come loose, so I decided to try and repair the unit. I examined the inside of the converter through the hole and saw that there was plenty of room around the hole itself, so I decided to place a flat piece of threaded 1/4” steel (which measured about 3/4” in width and about 4” in length) up into it.

I then took some of that sheet metal which comes in muffler repair kits and set about cutting two round gaskets which were a bit larger that the hole itself. I punched a hole in both of them, put some high-temperature RTV sealant in between them and put them aside. RTV (room temperature vulcanizing) sealant hardens when exposed to air and does not need a heat gun or other heat source to cure it.

I then took a bolt that fit the threaded hole (which was about 1/4 - 20 or so), placed a thick washer on it the same size as my sheet metal gaskets, put the gaskets over the washer, and carefully installed the “RTV sandwich” into the converter.

As I tightened the bolt, the threaded piece of steel pivoted a bit and got hung up on the wall of the converter which enabled me to tighten it enough to really seat everything nicely.

When the motor was started up again, the car was nice and quiet.

Many miles later, the repair shows no signs of failing. This turned out to be a very economical fix, especially when you consider the cost of a new converter. He even passed inspection with it.

Steve Dougherty Easton, Pennsylvania