Mercedes Catalytic Converters Rattle
Hello to all, I am looking for some insight on the Mercedes car catalytic converters. The first time this car came with this problem was on 8/9/2014 at 84,000 miles. The catalytic converters were rattling at an idle. We found the catalyst was loose in the housing. We gave the customer the choice between Maganaflow and OEM Mercedes and they chose the Magnaflow per the better price and warranty. We installed the MAGNAFLOW PN 93288 & 93289 converters. We performed an extended road test to heat up the converters to break them in properly.
On 5/16/2016 at 93,509 miles the car came in again with the same Converter loose/rattling problem. We removed the MAGNAFLOW PN 93288 & 93289 and upgraded to the Magnaflow 51422 & 51823. The newer part numbers supposedly were the OE grade converters from Magnaflow versus the standard grade that we had first installed.
On 1/26/2017 at 98,558 miles the car came in again with the RH converter rattling. We inspected the converters for contamination but could find none. The car is well maintained and does not burn excessive oil or coolant. We service it regularly with the recommend MB spec oil. This time we performed the 3 mode oxygen/converter test with Mercedes Xentry Diagnostics. The HO2S heater test passed. The HO2S aging test passed. And the Catalytic Converter efficiency test passed. The customer opted to replace the Converters under warranty so that is what we did.
Now for the current information. The customer has said that they are rattling again. The car is at around 115,000 miles. The customer still is not ready to put OEM Mercedes converters on it yet. It appears like there are only Reman converters available from Mercedes on this car.
So we are trying to think hard what the problem is? Is it just inferior quality in the aftermarket converters? We don't want to install the Mercedes converters just to have it happen to them as well. We thought of replacing the HO2S sensors ... but they did pass the Xentry test. There were never any codes associated with the problem such as converter efficiency or fuel trim codes. I do not know what grade of gasoline the customer normally uses. There are no exhaust leaks on the system.
What else could cause this symptom to reoccur like this. We are maybe overlooking something and would be open to your suggestions.
Thanks for your consideration.
The cats must be overheating. The fuel mixture control must be off just enough or it has an undetected misfire. After the second set i would have installed all new o2 sensors as a condition for warranty to continue. Passing the o2 sensor self test does not mean they are perfect. How many sensors over the years have you seen that did not set codes but caused drivability problems?
The original oem cats had issues with rattling, there’s more than one tsb for it. I have rarely had good luck with aftermarket cats on domestic vehicles And I probably wouldn’t have given the customer the option of putting. magnaflow parts on a Benz. At this point, I would not install anything other than oem cats on the car.
I have researched TSB's on this car and have come up with nothing conclusive. Basically the only TSB's I found on Identifix and Mitchel are related to how to pinpoint the noise as well as one that has you connect some vibration analysis tool to it for warranty purposes. Did you have a specific TSB in mind for this problem ... at least what it says about the OEM cats rattling?
Get the Benz converters. They say they're reman, but they're brand new. They just want your core, which you may get dinged for. Straight bolt in, perfect fit. Not to mention, you get the front and rear converter, per bank. We used to dread rattling cats on these vehicles and had many problems with aftermarket stuff. Benz has since dropped the price significantly, and the job is a confidence…
Only factory parts for these cars, I can not help you with why the aftermarket converters go bad, but we have never had an OE one come back with a rattle