Does it make the most sense to replace an old car's entire exhaust system all at once?

Question

Back story:

• The Check Engine light came on in my 2005 Chevrolet Malibu LS Sedan (V6 3.5L). I took the car to a mechanic #1 (M1), an independent shop. They replaced the EGR valve.
• A day later, the Check Engine light came on again. I took it back to M1. M1 inspected further and suspected exhaust system issues. Without my consent, they applied sealant (kind unknown) around some joints. Hypothesis: a leaking exhaust system caused the Check Engine light to come back. I was told to monitor and report back if it happened again.
• Days later, I took the car out for a longer drive. The Check Engine light was OK but I could smell a burnt chemical odor coming in after the engine was warmed up. It was worse when idling at a stop light, or when driving slowly, and without the cabin air recirculating.
• I brought the car back to M1. I told them about the bad smell. I said I have children and don't want them in the car with a smell like that.
• M1 raised the car up to show me where they had applied sealant. They said it will smell as it "burns off", but it hasn't stopped yet. They suggested it was a patch job merely to troubleshoot the engine code / EGR fix, and my exhaust system would need significant additional work.
• I took the car to mechanic #2 (M2), a dealership's service centre, and asked for a thorough inspection. I mentioned the likely exhaust issues.
• M2 confirmed the exhaust system has issues and suggested the sealant used couldn't be easily removed and that more or less I would need to replace the exhaust system. The exhaust manifold is OK, but from there to back should be replaced. Estimated parts & labour ~$2100 (Canadian), but suggested if cost an issue then I might prefer a shop that specializes in exhaust systems.
• I called mechanic #3 (M3), a franchise of a major "muffler" chain. I asked what it would cost to replace the entire exhaust system for my car. They were skeptical when I said I needed the entire system replaced. But, they did give me a ballpark estimate of ~$1400 just for parts. Labour and tax would bring it to the same ballpark as the dealer's estimate.

Anyway, given M3's skepticism about replacing the entire system, I did a bit more research. I came across this page at Consumer Reports. Here's the part I'm asking about with my emphasis added:

Inspect the exhaust system

If you’re willing to make under-car inspections, check for rusted-through exhaust parts that need replacing. Also tighten loose clamps. Do this while the car is up on ramps. If a shop changes your oil, have them make these checks. Listen for changes in the exhaust sound while driving. It’s usually advisable to replace the entire exhaust system all at once rather than to repair sections at different times.

Both the dealership and Consumer Reports seem to support the idea of replacing my car's entire exhaust system. However, the "muffler" chain franchise gave me the impression that it is unlikely necessary, and that I could bring the car in for them to have a look.

Does it make the most sense to replace an old car's entire exhaust system all at once? Are there bits & pieces that could be salvaged, or is doing that asking for trouble later? How should I proceed to get my problem solved in a cost-effective manner? I'd like to continue driving this car for another couple of years, at least.

Answer 1

Does it make the most sense to replace an old car's entire exhaust system all at once?

Considering your car is almost 10 years old, having to replace all of the parts in the exhaust system does not sound unreasonable, especially if your locality uses any type of road solvent during the winter months (they didn't in Montana where I'm from originally, but thought they might in Toronto).

Are there bits & pieces that could be salvaged, or is doing that asking for trouble later?

You could probably salvage smaller things like the isolators (rubber parts which suspend the exhaust without allowing much noise/vibration transference into the cabin), but depending on the shape of the other components, you probably are not going to salvage much else.

How should I proceed to get my problem solved in a cost-effective manner?

I personally would do it myself. If you have a friend who would willing to help you, you could probably do this work yourself with basic hand tools, jack stands, and a sawzall. All of the parts you'd need are readily available online from places like RockAuto.com, which also includes catalytic converter (though I don't know Canadian regulations on purchase & replacement). Stock replacement parts are available, which means you don't need to go to the dealership (affectionately called the stealership for obvious reasons). When I say they are "stock replacement", I'm telling you they are bent to spec, with hangers in the proper location. While a lot of work (just physically a lot of work), it really isn't that hard to replace these (though a lift makes it much easier). For about a 1/3 of the cost of what they are quoting, you could have the entire exhaust system replaced doing it yourself. Alternatively, you might also be able to barter some work out of someone as well ... nothing like going old school.

Unfortunately, exhaust systems are just one of those things which, if not made of stainless steel (which I'm surprised yours is not), goes bad after a while. The elements and the heat from the exhaust itself causes the metal to break down. Mother Nature will not be denied. If you took it to several mechanics which said the same thing, I'd be tempted to believe them. You may want to take it to one last mechanic (different, of course). Tell them you think you might be having exhaust issues and wonder what it would cost to get it fixed, without giving them further details. Also, ask them if they can show you what the problems are if they put it on a lift so you can see for yourself. This will give you a good idea of what is wrong and why they need to replace what they say needs replacing. Exhaust is pretty self evident due to rust and such. They should be able to point it out fairly easily.