19clk430

Hello everyone, i just recently purchased a 2001 clk430. the car has 70,000 and im hearing a rattling coming from underneath the car, like if metal were hitting metal. This only happens when i accelerate or rev the car, or after driving it hard. Not audible at idle or when cruising. After doing some searching on the forums, i think that its the cats going bad. So im just going to take the opportunity and have a exhaust custom fabbed. I just wanted to know what size piping should i use, 3in, 2 1/2? Also, what cats would you recommend for a custom setup? Is there a company that sells racing cats for our cars or maybe less restrictive cats that wont make the car throw up a CEL?

Thanks in advance
Randy

chem1441

If its the Cat converter, MB will replace it for free under the 8 year/80,000 mile emissions warranty.... just FYI...

MarcusF

At 70,000 miles, I would recommend taking it to the dealer who will replace the cats for free. They're covered by the 8 year/80,000 mile federal warrantee.

If you'd prefer a custom exhaust I would replace the cats with metal substrate converters. Metal substrate converters from a quality supplier (like Random Technology) will have much higher flow numbers than the OEM cats.

Lastly, I would use OEM sized tubing so as to ensure exhaust velocity stays high. Using oversized tubing "could" kill velocity, resulting in a large flat spot. If it does, you'll have to go with smaller diameter tubing until, by trial and error, you find what works. That's why good tuners get big money for complete exhaust systems - they've already done the R&D and know what sized exhaust works.

19clk430

Thx a lot for the help guys. I had no idea about the emission warranty. I really dont know much about the car and i thank you for your help!

Thunderdome66

I would also check your heat shields for the exhaust these cars have a few that could also cause these types of sounds when they become loose

newguy2008

This is exactly what it was for me. Heat shield was bent and I pryed it back and the rattling went away.

19clk430

Fixed the problem it was a heat shield hitting the metal lightly at acceleration. I just bent it back to place. BTW, does anyone know the size of the stock exhaust pipe's? I did some searching but im not really sure, is it 2.5in??

tastoto

so which heatsheild was it the one ontop of the exahsut or the catalyst