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replacing entire exhaust system... advice???

 
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kleve



Joined: 07 Jan 2002
Posts: 19
Location: Cleveland, Ohio USA

PostPosted: Sun Jun 19, 2011 10:14 am    Post subject: replacing entire exhaust system... advice??? Reply with quote

Due to rust I guess, the catalytic converter has started getting loud. Everything after it to the tailpipe is pretty rusty too. So I'm thinking the easiest thing is just to replace everything starting from the "front pipe with catalytic converter"-- what the Bentley's manual calls it.

My instinct is that I'd save a small pile of cash if I do it myself. I've replaced quite a few mufflers and other stuff in my life, so I don't foresee major challenges. But what tips and advice can people offer? I read that OEM catalytic converters work better than after-market. Have others here find this to be the case?

I don't have a spare car to run for parts, so I'm wanting to make sure I get all the new parts in the garage before I start taking things apart. Is the Bentley manual accurate in listing all the parts needed... or what else would I need? (Living in Cleveland, with all the rust car suffer here, I'm sure I'm going to need quite a bit of WD-40.)

The ride is a 1998 318i.

Thanks.
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kleve



Joined: 07 Jan 2002
Posts: 19
Location: Cleveland, Ohio USA

PostPosted: Sun Jun 19, 2011 10:40 am    Post subject: Reply with quote

Because it might make a difference in some situations, I should add that this is a 4-cylinder.
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PJK



Joined: 14 Feb 2002
Posts: 1829
Location: Shingle Springs, CA

PostPosted: Wed Jun 22, 2011 12:05 pm    Post subject: Reply with quote

I think that unless you have and are pretty good with an oxy-acetelene torch or wire feed welder this is a case where doing it yourself won't save you money. For this to be just remove and replace you will be dealing with OEM. Where I live the OEM cat is very $pendy. Aftermarket cats are ~$200 from Autozone.

I had failed smog and when I got the price from the dealer ~$2900 I thought the car was terminal. The alignment shop which I use recomended a smog specialist who welded in a new cat, tested the car, and mailed the certificate for $600. I was very happy.

If I knew about the $200 cat before I had it done I may have been tempted to try. I have a torch however as a welder I need to keep my day job.

To do the whole system you will be having to bend tubing.

If You have a muffler shop do it, insist that they put a coupling whic can come abert wit hand tools in the same stop where the OEM fitting is.

When I was a kid a muffler shop welded up the whole system. When in the future I had to pull a tranny I had to cut the pipe with a hacksaw, then go the shop to have it welded when I was done wit the tranny.

Phil
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kleve



Joined: 07 Jan 2002
Posts: 19
Location: Cleveland, Ohio USA

PostPosted: Sun Jun 26, 2011 3:25 pm    Post subject: Welding unnecessary Reply with quote

Maybe it's just since the internet, but welding pieces of the exhaust system together isn't necessary anymore. I've seen four or five online vendors selling "BMW fit" exhaust system parts and they're just the same as the original, at least they look the same. For example, the catalytic converter connects directly to the exhaust manifold at the front and the resonator/muffler pipe in the back. So replacing the entire exhaust system is really just replacing two parts, plus the nuts and bolts and a couple springs (where the catalytic converter and muffler meet). Welding parts together isn't necessary at all.

Given this convenience however, are the catalytic converter and muffler of the same quality functionally? I mean, is performance going to suffer? (I don't race, just want to let the engine last as long as possible and keep the pretty good mileage I've been getting.) Hmm... maybe this question requires an automotive engineer who's done actually comparison testing...?
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