supersnake83

Hello everyone,

I spent considerable time searching this and other forums and on google. I found many articles stating they had rattling from the exhaust, but many were the heat shields. I have an 05 Civic sedan LX Special Edition auto and I'm getting an exhaust rattle where the converter meets the first part of the exhaust pipe underneath the car.

I can get the rattling when the condenser and radiator fans are on (with the AC running, or without the AC when the car is hot and need the fans to cool). I also get the rattling when I'm idle in traffic, especially if I'm turning my wheel slightly (don't know why, but I guess it's because the engine/transmission is working harder at that specific moment).

I confirmed the exact place where the rattling is by jacking my car up and I had my GF turn on the the AC (to get the fans running), and I held the exhaust pipe at the location where the converter meets that first exhaust pipe (see pics below and red circles of where I'm talking about). Any idea what could cause rattling at that specific location?

I tried seeing if any bolts were loose, but they are tight, as well as rusty. The bolts around the converter are rusty too, so I didn't want to try and tighten them and one break off.

Any advise what else to check for? I don't think it's the heat shield, so my thinking is, could it be any mouns or something else adjacent to that specific spot making the exhaust bang against something else? No new work or anything has been done to the car, except a regular oil change I did 2 weeks ago. The sound has been going on for a while, but every time I heard it while in my car, I thought it was someone else's car making that rattle. Everything is stock on the car.

Thanks in advance.

ezone

High mileage, maybe 180k-250k? Rattle sounds like something much heavier than the flimsy tin heat shields?


I'd suspect the Catalytic converter......the substrate (guts) came loose from the steel shell, the rattle noise is coming from inside.

mac25

Grab the cat heat shield at each corner and try to pull it apart.

Sometimes they look like they are bolted together but the bolts/rivets rusted through.

It could also be the cat plate inside the cat. but that would through a code... do you have any CELs on?

You could also drive through an oil shop and ask for them to check it out.

Most good shops will do visual checks free in order to maintain good business.

supersnake83

120K on the odometer. It actually sounds like a light rattle. I couldn't hear it strongly for a couple months to think it was my car, but its not a heavy rattle.


What is involved with fixing the substrate/guts? Is this something a DIYer can do (with typical at home mechanic tools--with some extra power tool) or is this something I would need to take to a shop?

Thanks.

supersnake83

No CELs are on. I can give this a shot, possibly today to see if the CAT heat shields are the problem.

Thanks.

ezone

I've only seen a few of the 7th gen cats come loose inside and they were all at high mileage. Quite loud when it happened. No fix other than to replace the cat if that were actually the problem. (Also, no codes)

How about using a rubber mallet to tap on the exhaust while you search for the noise? Surely that could make it rattle if it is exhaust or shield related

supersnake83

So, I got back under my car and I could not find anything loose. I had the rubber mallet tapping things, and my long screwdriver trying to listen, and all rattling is coming from the connection between the converter and exhaust pipe. All heat shields were tight, and when the car is on and no AC, no rattle (except when the fans run to cool off the car). I had my GF turn the AC on/off several times and when the AC is on there is a rattle. Here is something I noticed, in the exhaust pic above with the long pipe, I don't have the union between part 4 and 12 where it uses 3 bolts. It looks like part 4 and 12 are welded together making one long piece (or is just one long piece). (i'm not sure if this is a problem or not, but my car has passed inspection/emissions every time without issue).

Now, one thing I can think of. The bolts that join the converter and exhaust pipe are pretty well rusted. It could be a breakdown in the connection because of the rust, making the connection looser causing a rattle (I tried tightening the bolts I could access, but they were already very tight), or it could be part number 8--the rubber mount that holds the exhaust pipe.

When the AC was on (or fans running to cool the car) the excessive vibrations cause the rattle. When I was under the car and AC on, I held the rubber mount and it stopped the vibrations. The rubber mount didn't look overly worn, but I don't know how tight/firm it is supposed to be. The rubber was flexible, but still slightly firm.

The other thought that just came to me, is could there be any worn motor mounts or anything that is allowing the engine/transmission to have excessive vibrations when the AC is on?

Other than that, I am at an impasse.

Thanks.

ezone

The rubber hangers...If not torn they are usually fine. They must allow the pipes to move around as the drivetrain moves.



How about (in the first parts diagram) bracket #1 and the two bolts #10, it is supposed to anchor the bottom half of the cat to the block......
Get it making noise, wedge a prybar to apply pressure or move the bracket, and see if noise stops?



In the second parts diagram you made a circle on the front end of cat assembly #4, but since you have an LX I think you really have pipe #11 in the car. No biggie.

The flex-joint (bolts with springs) between the bottom of the cat and the first pipe, is the cone shaped gasket (donut) worn and allowing metallic contact between the cat and first pipe? I've heard some make a rapid squeaking noise as the engine vibrates.

ezone

Engine off, flat ground, shifter in park, handbrake off....rock the car back and forth see if the pipes make noise as the engine/trans rock against the park stop?

supersnake83

Good to know, so that's off the list of possible issues. Thanks.

Investigating this has promise. I've lost my sunlight for today, so I'll give this a shot tomorrow.

You are correct! I don't know how I missed that. Yes, number 11 is what's under my car.

This is definitely a possibility. I couldn't tell if it was worn because I didn't take anything off, but this makes perfect since, especially since the noise is coming from that area. Do I have to take this off to check, or can I eyeball it. It's tight under there with no lift, so checking this could be a challenge.

Would this be an easy fix, meaning, is it simple to take apart to check (if I cannot eyeball it), then put back together (to confirm the gasket is the issue)? Or, should I only take it apart with the expectation to replace the gasket. I also won't have a lot of clearance under the car, so I'm not sure how those flex-joints are installed, or if I'll need a long torque wrench for anything. I'll only have the space under the car after the car is jacked up (and on stands), so if I take this apart, can the exhaust pipe hang without being damaged?

Thanks.

supersnake83

Did this. No noise. Thanks.

ezone

the bigger issue might be 'can it be taken apart without breaking anything?'
I'd expect to replace the donut gasket if it comes apart, and depending on condition maybe have new bolts and springs ready ahead of time in case they break, or round off...You know, have a backup plan if it has to come apart and goes sour.



How about using a length of tubing or hose held tight to your ear as a sort of stethoscope?
Get it making noise... Move the free end around to find where the noise is loudest

supersnake83

Yes, I'm trying to get ahead. As soon as I posted my last post, I took a look at the part numbers for the gasket, nuts, bolts and springs. I'm gonna call the three dealers in my area to see if they have the parts in stock, and who has it the cheapest so I can attempt this soon. Worst case scenario, I'll see what an indy shop would charge just for that. I don't know torque specs, but if anyone has them or know where I can find them, please let me know. Since the area is so tight underneath, I might have an issue with those rusted bolts.

Yep, from the first time I got under the car, I had my long flat-tip screwdriver as my stethoscope and it's how I identified the exact area that was rattling. It makes sense that the donut gasket is the problem based on location of where I heard the rattling, but I'm also gonna see if that part #1 from the converter is the issue too.

Thanks.

ezone

Tight enough the bolts can't back out on their own, and not so tight you break them.
16 ft lb sounds like a number used for 8mm hardware....(did not look, I've never put a torque wrench on one of these)

The bolts will screw in and bottom out on a flange.
The springs keep the flex joint pushed together and allow it to move.

supersnake83

I did another check today, and I was not able to replicate the rattle. It could be because every time I heard the rattle, I drove the car for a little while (like from work to home which is about 15 miles for me) and today I did not have to leave the house (as of yet).

I had a prybar with me and I was able to move the bracket slightly (like a couple millimeters), but since it was not rattling, I was not able to see if this was the issue.

I also got underneath today to see if I could eyeball the condition where the gasket goes and to confirm the bolt/nut (flange) count for if I were to replace the gasket (online listed I need 4, so this confused me, but I think 4 was for both the front and back of the exhaust pipe). I confirmed I only see two each of bolts, nuts, and springs, so that plus the gasket would only cost my like $65.00 locally from the dealer.

My new question is this, do these gaskets wear down, or is it typical wear for a car at the ~120K mile mark?

Also (and just making sure), if I were to attempt this repair, would removing the two bolts, springs and nuts be enough clearance to get the old gasket out and new gasket in, then put everything back together, or is this one of those repairs where I would have to drop the entire exhaust pipe to give me enough space?

I am okay with buying the parts and doing the replacement since I can't really pinpoint the exact problem, but it's nice that we've narrowed it down to a couple of possibilities.

Thanks.

ezone

Flexing/bending the steel, or movement because one of the bolts isn't tight enough?


2 bolts 2 springs 1 gasket. There are more elsewhere on the car but if you are only going to mess with this one joint you only need enough parts for this one joint.

There should not be separate nuts, they thread into the flange on the cat.

Most, no...A few cars, maybe.
I only tossed the idea out because I've seen it. IDK if it's actually your issue or not, that's for you to decide.

supersnake83

After reading this, it hit me, why didn't I check for a loose bolt, specifically the upper bolt (#10 on top) on the bracket in the Converter diagram when I got under the car earlier? Well, I don't know, but I do believe my issue is now solved.

Your question helped solve my issue (hopefully). The upper bolt was loose enough to turn by hand. I was able to tighten it with my ratcheting 14mm wrench and voila, hopefully problem solved.

I'll be going out tomorrow so I'll be able to test this after riding in the car for a little while. I'm glad I didn't go through all of that extra repair/replacement for nothing. I'm confident this is/was my issue. The looseness of the bolt was probably making the bottom of the coverter rattle against the frame.

Thanks a million, Ezone. Much appreciated for all of the help you provided.

ezone

Fingers crossed

supersnake83

I confirmed no more rattling. Thanks again Ezone for all of your help!

Issue resolved!

Andym

thank you for this.
I have had this issue since last year when someone replaced the transmission and I ended having to replace the 2 springs and 2 bolts holding it because one of the bolts was completely bent but the issue continues. Surprisingly i found it was missing bolt number 10 later and i said that's it finally but no, the Problem continues and it's right there. Tomorrow I will check every single item and take everything out and check that gasket too.

I have purchased all sorts of things trying to make it vibrate less and nothing made a difference into the muffler issue

4 New denso ignition coils, replaced again the transmission mount this time with a better quality one that comes with the weight balance in it and nothing.
Ordered 4 oem restored fuel injectors for $116 on ebay and waiting to install it tomorrow and hoping it will make a difference in fuel economy and else and again bought the PCV valve this time OEM because the beck arnley ones make an incredibly anoying noise.

Also purchased a power steering pump for the 4th time and hoping it will work fine. The other thing and thanks to this topic, i almost bought the idle air valve thinking my idle is getting low causing the muffler vibration when the A/C goes on and after the car is warm up enough.

sdaidoji

iTrader: (1)

have someone to check your chassis for cracks? (what i have seen was not in a civic, but possible)

Andym

Actually the noise is right there in the muffler and exhaust union where the bolts connect, I shake it with my hands before and it made the metal clanging noise. I believe the guy who mounted the transmision never installed the bolt number 10 and it might had caused other problems along the time because of that and i even also hear a loose piece of something from else where when i accelerate hard since the begining on the transmission transplant. I regret not doing the transmission switch myself at that time.