1991 300sl blink codes for bad cat

[rp930]

Trying to find out if my catalytic converter is bad. Problem is excessive heat from under console its starting to warm up down here in Alabama. Took it to a muffler shop and they said "JUST READ YOUR CODES" it will tell you if cats are bad. After 3 days of messing around building 2 different code readers I finally got one that works however I do not want to open up more cans of worms. I am not sure how to understand the codes as it tests several different systems.

[97 SL320]

Your car won't show any cat codes. Beginning 95 - 96 USA spec cars got OBD 2 that will show cat efficiency codes.

How long have you owned this car? Has it always been cold then suddenly got hot? ( under the same weather conditions ) Cats overheat due to external issues and not on their own. If the engine is running too rich / miss firing the excess fuel is burnt in the cat causing it to overheat. When this occurs you will feel a wave of heat / burning smell rolling out from under the car when you open the door and step out.

My 97 SL320 gets very hot in the console area under the now removed radio as does the shifter lever. My cats are not overheating and all heat shielding appears to be intact. This heat isn't coming from the heater core either as I have added a valve opposite the factory valve.

[rp930]

Thanks sl320,
Owned car about a year, heat is not noticable in winter, but in warm weather it seems to keep getting hotter the longer distance I drive. Sounds like we may have the same problem. I have installed new hood pad, made sure all weather stripping under hood, and insulation around firewall are in place as well as blower motor plastic housing. I remember last summer while stopping for red light I could feel heat on my arm that was hanging out window.

[97 SL320]

You will get some heat from under the car as the radiator air has to go somewhere. A overheated cat feels like there is a fire under the car. . . it is unmistakable.