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2000 SL500, 2001 S600, 2004 E320
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Discussion Starter #1
Driving on the freeway, large trash bag came out of nowhere and got under the car… quick look in my rear view mirror… nothing came out from behind. By the time I got home Major Stink of burnt plastic.

When I looked under the car this morning, there is like a shrink wrapped layer of plastic on both sides of exhaust, starting at rear cat converters and stretching another 2 feet behind, on the pipes. Pretty thick layer of hard plastic in some areas. I tried scraping it with screwdriver and it's not coming off easily.

I googled some solutions and Easy Off oven cleaner is mentioned a lot. However (if it gets the plastic bag off the pipe)… I fear potential collateral damage could be O2 sensor wiring harness. I would just let it burn out but that may take a while...

Has anybody had this happened? What is the easiest way to get rid of it?
 

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R129 500 SL 1991
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Low density polyethylene has a low combustibility, but when subjected to 500deg C (within operating temp of cat) it depolymerizes into gaseous hydrocarbons, and these readily ignite when mixed with air (containing O2), and the stuff will burn for a long time.

You’ve got a fire hazard. You need to get the thick crud off your exhaust. Don’t worry about the rest of the thin film, it will flake off gradually with time.

There are no effective solvents in practical terms for you. LDPE can be dissolved in toluene, benzene and other liquid alkanes but only at elevated temp over several hours.

Get the exhaust hot (bp of LDPE is around 110 deg C) and use a metallic scraper to get rid of the thick gloop.

Next time dodge the bag!
 

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I've had the same issue it sure is an annoying odor it will go away in time, I drive long trips so a trip to Phoenix or Vegas gets rid of it. In my case it turns to a white ash on the pipes.
 

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Discussion Starter #4
You’ve got a fire hazard. You need to get the thick crud off your exhaust. Don’t worry about the rest of the thin film, it will flake off gradually with time.
I've got most of this shit off, CATs are 95% clean and most of thick crap gone from the pipes. Certainly much easier to scrape it off with exhaust hot.

Hopefully the smell will burn off soon.
 
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