2005 Mercedes Benz SL500 catalytic converter

January 27, 2020 By , , ,

Repair or replace? We make informed, cost-conscious recommendations.

While many repair shops are quick to recommend immediate replacement when something goes awry, here at German Formula, we prefer to take a full investigative approach. Here’s a recent example:

The problem:

A customer arrived with a check-engine warning and a rattling noise from beneath their 2005 Mercedes Benz SL500. New, this car cost $92,000. Adjusted for inflation, that’s a $120,000 car in 2020. The car is still in great shape, with relatively low miles.

It was relatively easy to identify the problem. The bank 1 catalytic converter housing had begun to separate at the forward seam, which allowed the casing to rattle and probably let exhaust gases leak out before hitting the downstream oxygen sensor.

Some shops might recommend a replacement of the catalytic converter, at a cost of almost $2,000 with labor. But due to the fact that this is a fairly low-mileage car, we didn’t think the actual catalyst element would be out of commission. Bottom line: $2,000 seemed like a substantial financial hit just to close a seam. That said, the casing is made of the purest German stainless steel, so it’s not a garden variety weld.

Happily, where other shops would jump into replacement, we can make that repair.

Our solution:

After dropping the catalyst assembly, which spans the length of the car, we prepped and welded the casings on both banks 1 and 2. Then we hit the repairs with high-temp (1500F) paint to seal the afflicted areas, and reinstalled.

As hoped, the weld repair got rid of the rattle, and more importantly, the check-engine light. This repair cost the customer $450 out the door — a savings of $1,550 over replacement.

Here’s video of the catalyst casing, prior to repair:

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