can faulty catalytic converters cause massive muffler noise?

Question

I've been having troubles with a small 96' toyota tacoma 2wd "baby truck". I had the original muffler replaced which was rather quiet removed, and these guys put a Bosal muffler on it and it howled and was very loud at certain speeds right out of their shop . 2nd try same thing ... They are trying to get me to beleive that somehoe the catalytic converter is probably bad even tho it sounded fine up until the instant they messed with the car. What are the odds of their story being true?,.... That it's not a loud muffler, but really a bad catalyitic converter. I have had friends run cars without converters and they sounded ok . You think this is a plausible excuse / reason? or do you think if i went with an OEM muffler it would fix this? Thanks

Answer 1

Generally when a catalytic converter fails it collapses, and restricts the exhaust causing two things, a reduction in power, and a check engine light. Even with the converter off completely the muffler should be able to keep the engine quiet. (although the O² sensors would still give you a check engine light without it, and you wouldn't pass smog.)

Cause and effect. Effect, loud muffler. Cause, started right out of their shop. Get a second opinion, then armed with that demand they fix the problem, and that they fix it with an OEM muffler since a modified and excessively noisy exhaust CAN get you a fix it ticket. AND at no additional charge. If they bulk, contact whomever does the licensing of repair shops in your state.

Answer 2

sounds like your having an issue with the mechanics. When you replace the exhaust system you open yourself up for a couple "cracks".... literally. First, if you havent properly installed all the equipment or left loose bolts, or have faulty welding then your exhaust will sound TERRIBLE... not like a little howl or roar but instead like a high pitched almost grinding noise at certain parts of the RPMs. I had a friend this happened to and we had to get a second gasket to close off the gaps because of the improperly seated bolts/machining. This same issue can happen with the catalytic converter. If it is a newer truck that has an O2 sensor you should see a "check engine" light come up on the dash. If it is an older truck without the O2 sensor you won't see anything. Again, if you have cracks, improper welds, holes, leaks you are going to hear the noise again. You say the muffler is louder now though, it could be that the muffler is too hollow. This is a problem because it could impede your performance. I'd take it somewhere else for an estimate/opinion and see what they say. Unfortunately without actually being there I cant give you a straight answer seeing as there are many little things that could contribute.

Answer 3

Unlikly to be the catalytic convertor.

Check to see if the muffler is not leaking near any welds or clamped areas. If it is leaking it will have excessive noise and black residue eventually by the leak.

Most often a plugged convertor will cause alot of back pressure and eventualy keep a car from running or starting. A leak in the exhaust where it is weekest may occur and release some back pressure. Otherwise one with loose matrial inside can cause rattling and not tone down the exhaust sound as well either.

Put it this way though by installing a different exhaust muffler it won't cause the convertor to go bad instantly . Most of the time preformance mufflers have better air flow and a louder exhaust sound.
Generally this is because there are less bends and tube travel length though the internal chambers of the muffler and less fiber glass / sound deadening material to block flow of exhaust inside . Therefor preformance mufflers are much louder because they flow better not having extra bends inside and extra material to muffle the sound.Around 30-45 dcb louder on the average. In perspective the average car alarm is 120 dcb in loudness . If you want the stock low sound then go with a stock replacement muffler .
keep in mind the convertor could be bad also However it is only maybe a 10% chance that it is ; If the truck has power and the convertor is not getting excessivly hot / turning red sometimes after a drive at night then it is fine.

For preformance generally the convertor is cut off and a high flow muffler installed.which is federally illegal on street cars in most citys. This will result in a louder car or truck 99.9% of the time .Low sound and maximum preformance from exhaust is 2 way different aspects that don't work together. Either have a stock low flow exhaust with low sound and lose 10 - 20 hp or a loud one to gain 10 - 20 hp . Thats the basic choice with exhaust systems .The affordable one anyways.

You can switch to a bigger size system say 2 inch to a 2 and 1/2 inch . Although with stock mufflers and convertors you will only see maybe 5 hp difference.And the cost to do so usually is around 125.00 -200.00 for an exhaust shop to bend and weld in the new larger tubes in the system.

Borla makes a great low sound increase stainless steel tubed high flow exhaust with the convertor and muffler for many cars . It is around 10 -15 dcb higher in noise level than stock in most cases.with a 10-15hp increase . However you can Expect to pay from 750.00 -1400.00 for this low sound preformance exhaust system .

Answer 4

This is the description of the muffler. "For that great high-performance sound from your engine, a Bosal muffler is an unmatched value." You can buy mufflers to make sounds when your engine is running. You got the shaft know. They could have put a quieter muffler on.

They are flat out a ss lying to you. They want to take you to the bank for some more money . lol I do not know know where you are at , but tell them that you want to change mufflers for some quieter ones. Also, what warranty did you get. Also, what kind of money did you spend. Go to another muffler shop and ask them what Bosal mufflers would cost to the cheaper brand that are quieter. Then go back to the shop armed with this information. Tell them you plan to get a lawyer and sue. If your catalytic converters goes out, then your engine will have a hard time running. Normally it gets clogged up.

So check the prices with other shops as far as bosal and what a regular OEM muffler might cost. Then tell the SOBs at the shop you are thinking of going to a lawyer. Tell them you have been to other muffler shops and that they have told you what has happened. Tell them to change them to mufflers that do not sound loud. But remember to check with at least 3 other shops. And when you do, DO NOT tell them what shop you had your mufflers put on. Tell them if you have to, that you had them done by a cousin and you think he is lying to you about the mufflers and that the catalytic converter is making the sound.

Answer 5

The only thing that may cause a converter to make noise would be a hole in it but if this condition started occurring immediately upon muffler replacement, it's - without a doubt - a defective muffler. Those guys are full of it, and got used to deal with chevy people who like making as much noise as possible. I suggest you make them take their muffle back, and go somewhere else to get another one installed.
It's an older truck so paying a dealer $200+ for an OEM muffler may not be feasable but is the most fool-proof solution.

Answer 6

You probably have a cheap after-market muffler that changed the back pressure. A catalytic converter could cause noise and even breakup and damage the muffler, but most likely an OEM muffler will fix the noise problem.

Answer 7

What are the chances of the converter going bad at exactly the same time they installed the muffler? Come on.

Either they broke the converter when they installed the exhaust, or the new muffler is just loud.

Bosal looks like a good brand, though... they make factory and factory-replacement mufflers. They also make a performance line of mufflers, which of course will be louder. Find out which they sold you...

... and take it to a different exhaust shop. I think this one is jerking you around beacuse they don't want to be on the hook for bad workmanship.

Answer 8

Nope its the after market muffler, If the cat has been removed or hollowed out it would be louder but its the muffler if it didn't do it before. Also depending on what state you live in there may be a shop that can test the exhaust gases and they will tell you if the cat is working or not. Good luck hope this helps!

Answer 9

It may be the catalytic converter if there were holes in it. Did they check the resonator? That is the fatter tube ahead of the converter covered in mesh or perhaps it could be the donut that separates the header from the manifold. Sometimes when this ring splits, it creates a gap for exhaust to escape thus creating a loud noise effect.

Answer 10

If it's not the muffler itself, then it is most likely a hole in the exhaust system somewhere.... possibly in the catalytic converter or right at the pipe junctions.