98deville Posted May 4, 2008 Report Share Posted May 4, 2008 Which brand to go with? They have a Walker brand on Rockauto for $251. There's also a Magnaflow brand on Autopartswarehouse.com for like $75. Will a bad converter cause real bad gas mileage? Link to comment Share on other sites More sharing options...
Cadillac Jim Posted May 4, 2008 Report Share Posted May 4, 2008 The under-$100 cats usually require welding and use the flanges from your old cat. The higher priced one is probably a direct fit. Just get one that is OBD certified and your gas mileage should be fine. I would be sure that it has the capacity to let your engine have its horsepower, though. Most people on the East Coast don't understand Northstars as high performance engines. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
Texas Jim Posted May 5, 2008 Report Share Posted May 5, 2008 Which brand to go with? They have a Walker brand on Rockauto for $251. There's also a Magnaflow brand on Autopartswarehouse.com for like $75. Will a bad converter cause real bad gas mileage? Make sure you really need to have it replaced before you buy one. What makes you think it is bad? What problems are you having besides bad gas mileage? Magnaflow usually makes pretty good stuff. Check at your local muffler shops to see what they get for one. Link to comment Share on other sites More sharing options...
98deville Posted May 5, 2008 Author Report Share Posted May 5, 2008 Been hearing a real bad rattling noise from under the car..... Link to comment Share on other sites More sharing options...
lothos Posted May 5, 2008 Report Share Posted May 5, 2008 I believe that your rattling noise might also be caused by a loose heat shield. Someone correct me if I'm wrong, but I think that a bad cat will glow red at night, or if you pound on it with a rubber mallet you'll hear the insides rattle. I'd check it before paying for a new one. WARNING: I'm a total car newbie, don't be surprised if I ask a stupid question! Just trying to learn. Cheers! 5% discount code at RockAuto.com - click here for your discount! Link to comment Share on other sites More sharing options...
Regis Posted May 5, 2008 Report Share Posted May 5, 2008 lothos posted some good info about possibly being a heat shield. As suggested, strike the cat with a rubber mallet. If there is a rattle from inside the cat then you know. Otherwise it's probably a loose heat shield. Be sure to check the heat shield right behind the exhaust manifold. Mine was loose on one side. I have two large hose clamps holding it fast and it's been quiet for over 3 years now. "Burns" rubber " I've never considered myself to be all that conservative, but it seems the more liberal some people get the more conservative I become. " Link to comment Share on other sites More sharing options...
98deville Posted May 5, 2008 Author Report Share Posted May 5, 2008 will check for that 1st thing tomorrow morning... Link to comment Share on other sites More sharing options...
98deville Posted May 5, 2008 Author Report Share Posted May 5, 2008 just went under the car and checked for any loose heat shields and none were loose. I turn on the car and let it idle for awile and went back under there when I heard the rattle and it's the Catylac converter itself that makes the rattling noise, so I put a little pressure on the converter and it stop the rattle and as soon as I let go it rattled again.......The converter vibrates alot... Link to comment Share on other sites More sharing options...
adallak Posted May 5, 2008 Report Share Posted May 5, 2008 just went under the car and checked for any loose heat shields and none were loose. I turn on the car and let it idle for awile and went back under there when I heard the rattle and it's the Catylac converter itself that makes the rattling noise, so I put a little pressure on the converter and it stop the rattle and as soon as I let go it rattled again.......The converter vibrates alot... If the exhaust system vibrates that bad you probably have rough idle. Did you notice any idle-related change lately? I have similar problem, but will not touch the cat before I am 100% sure that's the guts what makes the noise and not the shield or something else. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
98deville Posted May 5, 2008 Author Report Share Posted May 5, 2008 No, Didn't notice any idle changes. It idles at 600rpms it's an 03 DTS with 62k miles on it...I tapped the converter with my fist and didn't hear any rattling . Link to comment Share on other sites More sharing options...
adallak Posted May 5, 2008 Report Share Posted May 5, 2008 No, Didn't notice any idle changes. It idles at 600rpms it's an 03 DTS with 62k miles on it...I tapped the converter with my fist and didn't hear any rattling . Same here... I am going to investigate it again tomorrow. I am also considering wrapping whole thing up with a coper wire to keep the shield tight. Keep in touch! The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
WarrenJ Posted May 5, 2008 Report Share Posted May 5, 2008 A "rattling" noise it a pretty good indication of a bad Cat. Poor fuel mileage is an even better indicator. I think your good old Uncle Sam requires manufacturers to warrant catalytic converters for 80,000 miles. If you're under 80K miles, this might be a freebee. Regards, Warren There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises Link to comment Share on other sites More sharing options...
Regis Posted May 5, 2008 Report Share Posted May 5, 2008 just went under the car and checked for any loose heat shields and none were loose. I turn on the car and let it idle for awile and went back under there when I heard the rattle and it's the Catylac converter itself that makes the rattling noise, so I put a little pressure on the converter and it stop the rattle and as soon as I let go it rattled again.......The converter vibrates alot... I believe there is a heat shield just above the cat. The reason I'm pointing that out is because the body of the actual cat is a pretty stout unit and if you could silence it by merely applying a little pressure to it then I would be inclined to think a heat shield is the culprit. You may want to have the car lifted and have someone else listen and look. Sound will bounce readily when the car is close to the ground and its source difficult to locate. Your regular garage shouldn't charge you anything for a lift and listen. At least mine doesn't. "Burns" rubber " I've never considered myself to be all that conservative, but it seems the more liberal some people get the more conservative I become. " Link to comment Share on other sites More sharing options...
98deville Posted May 5, 2008 Author Report Share Posted May 5, 2008 A "rattling" noise it a pretty good indication of a bad Cat. Poor fuel mileage is an even better indicator. I think your good old Uncle Sam requires manufacturers to warrant catalytic converters for 80,000 miles. If you're under 80K miles, this might be a freebee. Regards, Warren If the converter is bad where woud I take it to? The car only has 62k miles on it..... Link to comment Share on other sites More sharing options...
Cadillac Jim Posted May 5, 2008 Report Share Posted May 5, 2008 If your Cadillac has 62,000 miles on it and the catalytic converter is original (not one that the owner had replaced by someone other than a GM dealer) then take it to a Cadillac dealer. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
Texas Jim Posted May 5, 2008 Report Share Posted May 5, 2008 If your Cadillac has 62,000 miles on it and the catalytic converter is original (not one that the owner had replaced by someone other than a GM dealer) then take it to a Cadillac dealer. I may be wrong, but I think there is also a time limit on the replacement of the cats also. His car is a 1998 and may be past the time limit. Link to comment Share on other sites More sharing options...
98deville Posted May 6, 2008 Author Report Share Posted May 6, 2008 It's a 2003 DTS Link to comment Share on other sites More sharing options...
Texas Jim Posted May 6, 2008 Report Share Posted May 6, 2008 It's a 2003 DTS Sorry about that. I thought it was a 98 ... from your SIG. (98 deville) The cat should still be covered under the emmision warranty then. Link to comment Share on other sites More sharing options...
98deville Posted May 24, 2008 Author Report Share Posted May 24, 2008 The rattling noise really gets louder when the A/c is on..... Link to comment Share on other sites More sharing options...
Texas Jim Posted May 25, 2008 Report Share Posted May 25, 2008 just went under the car and checked for any loose heat shields and none were loose. I turn on the car and let it idle for awile and went back under there when I heard the rattle and it's the Catylac converter itself that makes the rattling noise, so I put a little pressure on the converter and it stop the rattle and as soon as I let go it rattled again.......The converter vibrates alot... Putting pressure on the converter... and it stops rattling. That don't sound like a converter problem. That sounds like a "SOMETHING LOOSE" problem. Putting external pressure on the converter should have NO EFFECT on an internal converter rattle. Link to comment Share on other sites More sharing options...
Regis Posted May 25, 2008 Report Share Posted May 25, 2008 I was wondering what happened with this thread. Jim, I was thinking the same thing as you (post #13). I hope he gets/got a second opinion before shelling out for a new cat. "Burns" rubber " I've never considered myself to be all that conservative, but it seems the more liberal some people get the more conservative I become. " Link to comment Share on other sites More sharing options...
Logan Posted May 25, 2008 Report Share Posted May 25, 2008 If the Cat is bad. I would expect a check engine light. Federal warranty on OBDII for the Cat is 8 years/ 80k. Logan Diagnostic LLC www.airbagcrash.com www.ledfix.com www.ledfix.com/yukontaillightrepair.html www.ledfix.com/ledreplacements.html www.ledfix.com/j42385toolrental.html Link to comment Share on other sites More sharing options...
Cadillac Jim Posted May 25, 2008 Report Share Posted May 25, 2008 You may not get a cat efficiency code with a cracked ceramic until it gets very, very bad, and then it's too late to save the mufflers. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
98deville Posted June 11, 2008 Author Report Share Posted June 11, 2008 Ended up being a bad Catylac Converter! Took the car in to a muffler shop the guy listened to the noise and told me it was the Cat. so I took it in to the dealership and they told me the same thing, so it's being replaced for free. I never had any codes or check engine light on or anything but I did have real bad gas mileage . Link to comment Share on other sites More sharing options...
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