So, I had the shop replace my catalytic converter, and a day or two later, I started hearing this noise, like a crackling or whistling sound, which seemed to be coming from the engine area (not sure though) whenever I accelerated. (Was quiet when coasting, and it got more intense the more I accelerated.)
I brought it back, they checked everything, including for leaks, replaced the gaskets on the cat, etc., etc., and said everything was fine. Must be a bad cat.
So I did a warranty replacement on the cat and they put in a new one. But the noise remains.
They spent some time examining it and trying to find where the noise is coming from, but were unable to. (The mechanic was sick yesterday and went home early, so he wasn’t able to spend a lot of time with it. They’re going to have someone else spend more time with it today.)
I just thought I’d post it here in case anyone has experienced something similar.
Here is a video I made while driving which shows the noise. It’s a little hard to hear because of wind interference. You have to either listen to it on a computer or with ear buds. Listening on a phone you can’t make out the noise from the wind.
On a 20 year old minivan…it could be a lot of things.
I wonder if maybe in moving the exhaust pipes around, they might have loosened something else upstream, like the exhaust manifold. That’s where I’d be looking.
Whistling sound, that seems more like some sort of air or exhaust leak, musical instrument effect. Diy’er me, I’d be first checking the connection at the exhaust manifold, same as @ledhed75 suggests. Remember,just b/c it happened after the cat change-out, that may have nothing to do with the cause, just a coincidence. I had a really loud whistling sound from a loose valve cover fastener one time. Not exhaust related. Crackling, that could be the exhaust system rattling. Broken/loose/incorrectly attached exhaust hangers.
Other experiment ideas, if you can get it to happen in the driveway, does the sound change
When increasing the engine RPM, the noise increases, becomes more intense. Doesn’t become louder, just more intense. Maybe that’s louder, I don’t know. But you can hear the change as you press down on the accelerator more.
Just a thought…
If you only had the Cat replaced and not the whole exhaust. It is possible that the material in the Cat broke off and traveled down the exhaust system and is partially blocking the exhaust flow making the sound.
My method for checking for exhaust leaks, apply soapy water with paintbrush to suspect interfaces. Bubbles appear if leak. Helps to have helper partially obstruct tailpipe at the same time. Best done soon after starting cold engine, when exhaust system still on the cold side, b/c, less likely to get burned, & when exhaust gets really hot bubbles form just b/c the water boils.
A length of rubber hose, I use 5/16 or 3/8 fuel line most of the time, will pick up any exhaust leak I have ever looked for…
You never said what engine, but I remember the 3.3/3.8L engines had issues with the exhaust manifolds warping and causing leaks, or cracking causing leaks… May be when they replaced the down pipe it disturbed the cross over pipe (V6 only, connects the left to right manifolds) and now it is leaking…
The interesting thing is that the noise didn’t happen right away when I picked up the car, but instead it was a day or two later that I first noticed it.
They do have a smoke machine and they already used that. The soapy water test was an additional test (I suppose if the leak is minor and the smoke was not detected).
UPDATE: Well, it’s been several days already, and no progress. The service manager was out sick for a couple of days, but is back. But every time I ask him for an update, he says he’ll check, but then doesn’t get back to me.
I think they just put my car aside and are working on other stuff, and are stumped about what the problem is. So what should I do?
The problem started a day or two after they replaced the cat, so it seems it’s something they should deal with. But they don’t seem to be making any progress. Any advice?
If it was done at an independent shop, then I would get a second opinion… If it was done at a chain shop, then I would take it to another shop and have them check it out under warranty, maybe even call the district manager to get them involved… One good thing about chain shops is you can often get upper management involved to get the issue delt with… with Indy shops you are just at their mercy…
Also if the service manager was out sick for a while, they/he may be trying to play catchup and just needs a little more time…
Service manager said they’ll be working on it today. So I guess we’ll see how it goes.
It’s an independent shop. They’re usually reliable. I guess with the service manager out the mechanics prioritized other things. I guess we’ll see what happens today.
Just heard back from the service manager. Said the noise is coming from the rear exhaust manifold. Said they listened with a stethoscope and is sure that’s where it’s coming from.
I asked about whether replacing the cat could have caused it, and he said that they just bolt four bolts onto it, so it wouldn’t have caused it. Said probably because the manifold was old.
The noise didn’t start for a day or two after the cat was replaced, meaning if something had been jarred loose when they replaced the cat, then it might have come completely loose over the next couple of days with the car bouncing around while driving.
So he said they were going to replace both manifold gaskets, even though only the rear one has the leak, because of the age.
My valve cover gaskets have been leaking for a long time, and he recommended doing those at the same time, so I agreed to do that.
The whole thing was going to cost $1080. I asked if he could cut me a deal on it, and he brought it down to $900.
Interested in hearing people’s thoughts on this.
Is the problem the exhaust manifold gasket developed a leak? Or the exhaust manifold itself cracked and leaked? I’m presuming the first, only the gasket needs replacing. $900 for 2 new valve cover gaskets and 2 new exhaust manifold gaskets seems reasonable, presuming this is a v-configured engine. Quite a bit of labor involved.
Both exhaust manifolds are bolted directly to the engine’s cylinder head, & the constant heating cycles, driving/parking/driving/parking can work those fasteners loose, which allows a small exhaust leak at that interface which in turn damages the gasket. Suggest to ask shop to monitor those fasteners in the future as part of routine maintenance to help prevent them for getting too loose. Not much can be done to prevent the valve cover gaskets from springing a leak; they seem to eventfully develop leaks as a matter of course. How leak prone those are seem mostly determined by the engine’s design. They leak much sooner on my Corolla than on my truck for example.
Yes, it seems to be just the gaskets. I’m puzzled though as to why this would happen right after the cat was replaced, if they didn’t damage anything.
The mechanic said something about more airflow with the new cat, so the sound wasn’t noticeable with the old cat. But that doesn’t make sense, since the noise didn’t start for a day or two after the cat was replaced.
Seems something may have been knocked loose or damaged when they replaced the cat, and it took a day or two to completely come loose.
It doesn’t make sense that the gaskets needing to be replaced would only manifest right after they changed the cat. That’s why I was wondering what people thought about all of this. Doesn’t make sense to me.
Jostling the exhaust system to replace the cat might have opened up a small but already existing exhaust gasket leak. But that would have happened soon anyway. Sort of like when you bite into a piece of bread and your tooth filling falls out. You go to the dentist saying “all I did was chew on a piece of soft bread!”. The dentist replies it was already loose & was going to fall out anyway, and the bread chewing just happened to be when it did.
OK, good to know. I don’t mind paying, as long as it wasn’t their fault.
Do you have any ideas as to why the noise wouldn’t have manifested for a day or two after they replaced the cat? Car sounded fine when I picked it up and when they test drove it.