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DIY Catalytic Converter Replacement?

Yesterday my 1995 Toyota Corolla (which runs well otherwise) started making the loudest rumbling exhaust sound I’ve ever heard whenever I stepped on the gas pedal. It also felt like it had trouble accelerating when I would try to get going after a stop. I took it to a mechanic right away, who says it needs a new catalytic converter and resonator pipe, and that this will cost $700-$800.

My boyfriend says this is a repair he could do. He has done some car repair and worked with a mechanic before, so I am considering trusting him on that, but I don’t know what types of repairs he’s done before and I know he has never worked on this model. What would you take into consideration to help you decide whether or not it would be safe to attempt this repair at home?

1 The age of the car
2 The difficulty of the repair
3 Building a trusting relationship
4 Cost savings
5 Tools, jack, safety jacks available

It’s not rocket science.
He could save you a lot of money.
He could be your hero if you trust him.
It’s a 22 year-old car (a veritable senior citizen in car years)!

I say let him have a go at it.

Sure. Any insight regarding #2 in this case? I’ll make sure he has all the necessary tools and equipment–mostly I posted this to get a second opinion on whether this repair is something an intermediate amateur can reasonably and safely accomplish if it’s not something they’ve specifically done before.

Safety is critical, he’ll be working under the car and yanking on things, so he has to have a good pair of jack stands. Have you priced out a replacement cat at a parts store? You might call a nearby muffler shop and see what they’d charge. If it’s not much more I’d let them do it.

It’s not complicated work, but it’s no fun dealing with all the corroded parts, nuts, etc.

Me, I’ have the shop just put in a straight pipe in place of the resonator, it has a muffler.

@elm90-Read texases post twice. The key question is how would you feel if something were to go wrong and this vehicle fell and injured someone trying to help you save money.

I had a catalytic converter and tail pipe installed by an independent muffler shop and it was not that expensive.

Depending how skinny he is because he’ll be under the car and need ramps at least. But I’ve done it and not that big a deal. One issue though is I don’t see how it would cause a power loss problem. Very noisy yes if the joint rusted through, but he needs to verify there is a real problem with a rusted out cat.

Before any attempt is made to do this repair at home, inspect the hardware at the catalytic converter flanges.

Sometimes this hardware is so rusted that conventional hand tools are useless in removing them, and instead they must be cut off.

So, unless you have the means to remove this rusted hardware, it’s best to have a shop replace the exhaust components.


Because the mechanic that looked at this, mentioned no issue that would cause a lack of power, I’ll presume that there is no problem, other than the resonator pipe and converter.

This should be a pretty straight forward, simple job…that should take little expertise.

I’d let him do it, but stress that you want him using every safety step available.
Jack stands, ramps, and safety glasses. There will be lots of rust breaking free that can get into his eyes.

Also check out I found the parts there for less than $200 depending on the engine size and vendor.

Then you can take him to a really nice overnight trip with the savings.


He should have no problem, having worked with a mechanic before. There’s no mystery to changing a cat converter.

Sincere best.

This is potentially a relatively simple job. As others have already mentioned there are several things, especially rust, that can complicate the job. I happen to live in Southern California where rust isn’t usually severe and I’ve removed and/or replaced a number of catalytic converters (and other exhaust components) from Toyotas and Hondas (bolted). I’ve been fortunate in that so far I’ve never had a big problem removing catalytic converter fasteners. However, exhaust systems are inherently rusty so I know my luck can run out anytime. I will say that unless the fasteners are in excellent condition I will replace them with new ones when I reassemble. My point is the project is doable but it depends.

I had a split converter and the muffler bender guy welded it back together for $10, 5 years I drove it after that, no problem. Maybe you can see if that is an option.


What state do you live in?

Depending on your location, you may have to buy an “approved” catalytic converter, which could be very expensive

A bolt in converter on that car probably also includes a substantial portion of the exhaust pipes. It’s a lot easier to remove a cat if it’s on a hoist, versus on jack stands

Provided he actually possesses the skills and tools to do the job, letting your BF replace your cat could save you some significant $$$. It’s not overly technical work, and there’s not much that can be damaged in that section of the car if he makes a mistake, so the main risk to you is that he won’t finish successfully and you’ll have to take the car to a shop to get it finished. Which you’d have to do anyway. You’d only be out the extra time off the road. I concur w/the advice above, make him aware of the cautions above, then let the bf have a go at it.

A couple of cautions of my own. First, the performance problem might not be the cat. There are several tests a shop can do to verify the cat is the most likely culprit, but the best test to prove it’s the problem is to remove it entirely, replace with a straight pipe, and see if that solves the performance problem. If it was my car I’d probably do that, even if it took extra time. Might save on the expense of a new cat.

Second caution, make sure the replacement cat is compatible w/your state’s emissions law requirements. Here in Calif only certain vendor/part numbers are allowed. And when you take your car to the emissions testing facility they check those numbers, and if the cat isn’t one of the allowed versions, you automatically fail and can’t register your car until you have an approved version installed.

Oh, for the final caution, I’d advise the $$$ saved be invested in some nice dinner dates for the both of you at the local Chez French Bistro. Cheers!


“I don’t see how it would cause a power loss problem”

very simple . . . if the cat is plugged up, the engine can’t “breathe” properly

suppose you were attempting to run a race, and you were forced to exhale through a straw


For the record, this is the exhaust system on the '95 Corolla, North American version.
Fortunately for the OP and her BF, it isn’t a later model. On later models, the entire system from the exhaust manifold to the muffler needs to be disconnected just aft of the exhaust manifold, and we all know how much of a PITA those manifold studs can be. On the’95, the flange bolts fore and aft of the converter can simply be cut and the converter, metallic gaskets, and nuts & bolts replaced.

With our rust in the Buffalo NY area I usually use two long breaker bars and two 6 point sockets pulled in opposite directions and they snap right off. I don’t have a cutting torch and it is much faster than a metal cutting blade.

I would suggest a set of ramps to pull the car up on . If your exhaust is like the illustration posted it appears as though 4 bolts will have to be unscrewed , snapped or cut off . Yes , make sure he uses safety glasses , I’ve had to have metal dug out of my eyes twice . The second time I was wearing safety glasses but not the kind that fits tight to the face around the eyes . If he has any mechanical ability , I think he can handle this job .

To me, safety goggles and good solid ramps are the most important.
Everything else is secondary (and quite doable).

If the BF doesn’t have a decent jack, ramps or jackstands, and tools to wrestle their way through the more than likely prevalent rust then it might be a good idea to just bite the bullet and have someone do it.

Personally, I hate doing exhaust work and especially on a car that is not on a lift. The aggravation factor goes up quite a bit sans lift.

Granted, it’s much easier on a lift. But I’ve done many exhaust repairs over the years with the vehicle securely on jack stands, and it’s certainly doable. If it were a later model, I’d be more inclined to avoid doing it, but on this design it isn’t really a problem.

My record? On my old pickup once I changed my exhaust system complete from the cat back in 20 minutes start to finish, including jacking the truck up and down. I was temporarily living in an apartment and working on cars in the parking lot was prohibited… so I had to get the job done fast. My trick? I had changed the system before and used stainless bolts and nuts with anti-seize. The bolts and nuts came apart as if they were brand new. No muss, no fuss.