Clunking/rattling noise under any kind of deceleration

[dmention7]

I recently had my MSP into the dealer to have the turbo replaced under warranty (leaking oil and almost no boost), and I had them check on a noise I've been hearing since I bought the car in April, but had little luck diagnosing myself.

The best way I can think to describe it is a clunky rattling noise from the front driver's side corner that occurs whenever I am decelerating--coasting, braking, in gear, out of gear, clutch in, clutch out, always. The rattle seems to follow the speed of the wheels, as opposed to the speed of the engine--at 70mph it's a sharp rattling, and as I coast it slows to a more of a rhythmic clunking by around 30mph. It disappears completely below about 15mph. At any speed it's less pronounced if I pop the car in neutral, but it doesn't change the pitch/tempo of the rattle. It's much more noticeable with the windows shut, which leads me to believe I'm hearing the source of the rattle resonating through the floor or something. I can also feel it in the shifter.

So, back to the dealer--they wanted to pin it on my aftermarket catless midpipe banging on the cross-member, which sounded somewhat plausible to me since I've heard of that issue before. But I was still a bit perturbed by the other characteristics of the sound, and the fact that I had been hearing the noise when the exhaust was completely stock, so I insisted that a tech ride with me, and they take another look to rule out all other possibilities. The next day, they told me they had used some different nuts and washers to secure my midpipe a bit better, and installed new shifter bushings, but they were still convinced the problem was the midpipe/crossmember. I thanked them for taking another look, and took the car home. But when I popped it up on ramps to inspect the midpipe for myself, I couldn't find any evidence that it had ever contacted the crossmember--it's painted/coated, and there is a long scratch from when I was installing it, but not a single nick or ding that you would expect if it was rattling against the crossmember constantly.

(I should also note that I have installed street unit front/rear motor mounts, but had been hearing the rattle before those installs.)

Does this sound familiar to anyone? I've had no luck tracking down the source of the noise myself, and I have a feeling that any other dealers I visit are just going to try and blame the noise on my aftermarket parts, especially since I didn't report the noise right away.

Thanks in advance for any ideas!

[eddiejoe56]

Does the noise occur more during turns than going straight?
If so, it could be you CV joints on the drivers side axle.

[macklum]

You may want to check the inner CV joints at the tranny . These will give those symptoms you are describing

[msp35]

Check everything they would have had to remove. Radiator, fans, SMIC, Piping, EGR, coolant lines, maybe even the plastic splash guards underneath,
and obviously the turbo/dp/EM.

[crackerjakx]

Check everything they would have had to remove. Radiator, fans, SMIC, Piping, EGR, coolant lines, maybe even the plastic splash guards underneath,
and obviously the turbo/dp/EM.

+1...

When I took my car in to get the turbo replaced the dealership didn't tighten the radiator fan back down. So, it wouldn't surprised me if something that was recently worked on was rattling from being loose.

[dmention7]

Does the noise occur more during turns than going straight?
If so, it could be you CV joints on the drivers side axle.

Happens at all times--I've tried turning while I hear the noise, but it doesn't really seem to have any effect.

I've visually checked the CV joints, and saw no signs of torn boots or leaking grease, but I'm not an expert. Are there any other external signs or tests that would indicate a CV joint is going bad?

Also, since I've been hearing the exact same sound since well before I ever brought it to the dealer, I'm certain it's not something they did or didn't do.

[peajay]

how do your side motor mounts look?
double check your shifter bushings all around and that the bolt is tight.
maybe a wheel hub? (tho it's rare anymore to get one that clunks rather than growls)

[dmention7]

Haven't checked the side motor mounts too closely, though I was planning on ordering SU's side mounts to finish off the set. Last time I looked though, they didn't appear to be trashed to the point of producing the sound I'm hearing. Should be easy enough to remove and inspect them though.

The dealer actually installed a new set of shifter bushings when they were trying to diagnose the sound, so I doubt that's it as well.

As to the wheel hub, are there any external signs of failure that I could check for?


Appreciate the replies so far, everyone!

[livelyjay]

Jack up the front end of the car and put it on jack stands. Grab the wheel, while it's still connected to the hub, and wiggle the wheel from the top as hard as you can. Now turn it by hand. If it doesn't make any noise (other than the rotors) and doesn't wiggle, it's not the hub.

[msp35]

I'm an idiot. I just had to reread this. Your exhaust may be hitting the tunnel right under the firewall. My ghl dp did this pretty bad until I put in some MM inserts. I could feel it with my left foot like someone was under the car hitting it with a rubber mallet.

[livelyjay]

The Vibrant exhaust also has a tendency to hit the cross member if you don't have the poly exhaust hangers (e.g. Kartboy hangers).

[dmention7]

I've got poly front/rear motor mounts, as well as Kartboy hangers. Honestly, I hadn't checked whether the exhaust could be making contact with the exhaust tunnel or heat shield--I was focused on whether it was hitting the crossmember. I'll add that to my list of things to check when I put the car up on jacks.

How about the inner CV joints... are there any external indicators of failure that I could check for?

Thanks :)

[Kaldonis]

How about the inner CV joints... are there any external indicators of failure that I could check for?

Thanks :)

I would imagine if your CV joints are the problem that your CV boots are in pretty rough shape, which you would be able to tell just by looking at them/feeling them. You would probably have to either jack up the car or get up on some ramps to have a good look though. The CV boots are like right behind the brake rotor on your front axle. You would want to check them for any cracks, tears, etc...

[dmention7]

Okay, that's what I figured. I'll take a closer look, but I've been under on a weekly basis for awhile now, but I've never noticed any problems with the boots.

[dmention7]

Okay, well I put my car up on jacks just now. The CV joints look absolutely fine. I can't get any noise out of the wheel hub either. What I did find, is that if I rock the front driver's side wheel gently back and forth (with the passenger wheel still on the ground), I can hear a slight metallic clunking from inside the transmission--and it sounds like it might be from the diff housing. There is about 1/4" of rotational play in the wheel, and it makes that little clunk at each extreme.

I had my GF rock the wheel back and forth while I sat in the driver seat with the windows up--the sound was quite audible, and sounded virtually identical to the sound I hear under deceleration, and from the same location. I feel 90% confident I've tracked the source of the sound down.... what will make me 100% sure is if someone can verify for me that it's NOT normal to hear a sound from the transmission when you rock one wheel back and forth. Especially one that is clearly audible from inside the cabin.

[dmention7]

Monday morning bump.... I've had it suggested in another forum--with a fair amount of certainty--that the inner CV joint is failing, even though the boot appears to be intact and in good condition. Any thoughts on that? I just want to be able to make as firm of a case to the dealer as possible, since they already tried to pin it on my exhaust.

[macklum]

You may want to check the inner CV joints at the tranny . These will give those symptoms you are describing Didnt I already say that . My 1st gen did the exact same thing it was the inner right CV joint that was starting to expire , I replace it with a remanufactured drive shaft rather than just replace the CV joint and now more noises ,vibrations .

[dmention7]

Hehe, yeah, I guess you did. I just assumed by check, you meant inspect the boots. I was under the impression that when CV joints fail, a torn boot is usually the cause, but it sounds like that's not the case.

[macklum]

Hehe, yeah, I guess you did. I just assumed by check, you meant inspect the boots. I was under the impression that when CV joints fail, a torn boot is usually the cause, but it sounds like that's not the case. The inner boots dont usually tear , they will however wear out causing an off balance on the shift thus the vibration , they tend to go without much warning

[dmention7]

alright, thanks for the info!

[dmention7]

*sigh* Well, they agreed to take it back in, but the service manager seemed to be just as committed to the idea that it's my exhaust as he was before.

The clincher in their eyes, is that when they were test driving it to diagnose my turbo problem, they didn't notice it then. Which honestly doesn't surprise me too much, because they weren't looking for a rattling problem. I know for a fact that it was there before I ever thought about installing a midpipe. I guess choosing not to complain about it right away is coming back to bite me in the ass. At this point, I'm really hoping it's just my exhaust, because they don't seem very eager to look at anything but the evidence that points to the exhaust...

Frustrating, because they don't even seem willing to entertain the possibility that there's a problem, as long as they can loosely pin it on an aftermarket item. At least they're only holding the threat of making me put EVERYTHING back to stock, rather than voiding my warranty or some other supreme bullshit.

[dmention7]

So, here's the latest entry to this little saga.

When I talked to my service manager on monday, he asked me to bring it in again, and they'd take a look. The last thing he mentioned was calling mazda to see what they thought, and if they would make me go back to stock.

So I rolled in today, all ready to do battle--had all my arguments together for how my mods could not possibly be causing the noise... raised the pipe way off the crossmember, shoved a chunk of coolant hose between the pipe and crossmember, sound persists even while coasting with the engine off and tranny in neutral... everything. And as a last ditch effort, I was ready to try and convince them to let me at least leave the rear mount in, because it's a bitch and a half to replace.

Anyways, after watching CNN talk about the Dow Jones plunging 300 points today (OMG! SELL SELL SELL!!!!!) for half an hour, he comes upstairs and lets me know that they want to take apart the differential first thing next week. Apparently mazda's people agreed with me that it was at least unlikely enough that my mods were the problem that they're willing to authorize having my diff inspected.

It appears that things are looking up for me... I'm just glad I've been keeping persistent but polite about this whole thing. I'm also returning to my original highly positive opinion of Morries' service department. The service manager I've been working with has been a lot more accommodating than I would expect from a dealer (even if they frustrated me a bit with their focus on the exhaust pipe). So, best case scenario I'm looking at a brand new LSD and a week or so in a loaner.... but we'll see what happens.

[dmention7]

Update... Looks like the problem wasn't the diff itself, but the reverse lockout plate had broken off, and was rattling against the diff's ring gear. That would explain why I've accidentally ground against reverse a couple times while trying to make a 5-4 downshift.

Anyways, parts will be in tomorrow :D