Rattling Cats
Thread Starter
Junior Member
Joined: Mar 2008
Posts: 39
Likes: 3
2000 E320, 1997 E420, 2007 E550, 2009 E350
Rattling Cats
1997 E420
165,000 miles
My cats began to rattle around two months ago. Shortly after that I started getting codes, mainly 300, 305, 306, 307 and 308. I would also get a 410 but rarely. I bought the MagnaFlow #99205 Universal Cat and had a local muffler shop weld it in for me on the drivers side.
Now (after repair) I took off and accelerated heavily and almost immediately I had the same issues. The fault codes came back and I can hear the cat rattling and I am getting the same codes. First I get codes 300 and 307, and if I continue running it I will get 305, 306, 308 and sometimes 410. If I reset the codes, the CEL goes out and the car runs fine until instant, heavy acceleration. The sequence after heavy acceleration is I hear the cat rattling for a few seconds so I back off the accelerator, then heavy acceleration until the cats rattle and it throws the codes again.
Can anyone tell me what to check next?
165,000 miles
My cats began to rattle around two months ago. Shortly after that I started getting codes, mainly 300, 305, 306, 307 and 308. I would also get a 410 but rarely. I bought the MagnaFlow #99205 Universal Cat and had a local muffler shop weld it in for me on the drivers side.
Now (after repair) I took off and accelerated heavily and almost immediately I had the same issues. The fault codes came back and I can hear the cat rattling and I am getting the same codes. First I get codes 300 and 307, and if I continue running it I will get 305, 306, 308 and sometimes 410. If I reset the codes, the CEL goes out and the car runs fine until instant, heavy acceleration. The sequence after heavy acceleration is I hear the cat rattling for a few seconds so I back off the accelerator, then heavy acceleration until the cats rattle and it throws the codes again.
Can anyone tell me what to check next?
Thread Starter
Junior Member
Joined: Mar 2008
Posts: 39
Likes: 3
2000 E320, 1997 E420, 2007 E550, 2009 E350
Not a chance. You say that though you drive a 99 E300 like mine!I just need to know how to identify blockages etc to get it running right again.
By "repair" I mean replaced the drivers side Cat with a universal cat (Magnaflow #99205).
By "repair" I mean replaced the drivers side Cat with a universal cat (Magnaflow #99205).
Last edited by georgiabenz; Jun 28, 2017 at 04:51 PM.
MBWorld Fanatic!
Joined: Aug 2005
Posts: 1,274
Likes: 26
From: Hawaii
1996 E320, 2018 Ducati Panigale V4S, 2012 1199 Panigale
I always find it best to have the muffler shop diagnose the rattle. They are super good at doing it. My car ended up having rattles in both cats, and they ended up just installing test pipes and the rattle was gone.
