[liver]

I had a rattle after some service done by the dealership and in that case they just failed to tighten down the covers all across the bottom of the car. Sounded way worse and I could not figure out where it was coming from, but a third party indie shop find all the law hardware in an instant.

I would not blanket recommend for or against dealerships, but instead make sure to do your diligence on a dealer you would any other mechanic. Turns out I'll never deal with the local dealer here in Portland again, and will only use the indie shop I was introduced to later.

 

[4Canada]

So I looked more into the history of the car, and in one ad it states that it has an Alfa works stg1 tune. But I pulled the ecu and there’s no Alfa works badge or markings and it looks oem. So I dunno if maybe it had a tune at one point and maybe stock ecu was swapped back? Anyway to tell what map is on there? Also I changed the plugs and it looks like it had a set of Brisk iridium’s. I switched out to oem but no difference.

Anyway, Here’s the best recording I have of the sound so far. Happened very repeatably on my drive last night. In 2nd-4th gear under part throttle and full throttle acceleration. Weird part is this morning I took a drive and I could only induce the sound a couple of times and it wasn’t as severe. Morning was slightly cooler is the only difference I can think of. Does it sound like possible pinging/detonation? Wastegate rattle? I’m really at a loss on what it could be lol.

Alfa rattle

youtube.com

Can you use watch the boost gauge when you get this noise? Any change in level?

 

[Rusco7]

I just listened to your latest clip through my headphones. Sounds very much like a boost leak, it’s in unison with the turbo spooling up. Check all hoses and dump valve

 

[Flash]

Wouldn't that throw a light?

 

[STL4c]

Hey OP, you bought my old car. Didn't have that issue when I traded it in. And by the way, the Brisk Iridiums were installed at 39K, and they seemed to run better than the OEMs for me. The ECU was put back to stock when I sold it, and I sold the alfaworks ECU to another member on this forum. Only other "mod" is a BMC filter (and the touchscreen radio). If you have any other questions about the car's history, I'll be glad to tell you what I know, just send me a DM. I'm not on here a ton anymore since I don't own a 4C anymore, but I'll check in periodically.

 

[4Canada]

Wouldn't that throw a light?

I had two long splits in the boost hose from IC to turbo, and that didn't produce any codes.
(was a silicone hose, too!)

 

[qwikrex]

Hey OP, you bought my old car. Didn't have that issue when I traded it in. And by the way, the Brisk Iridiums were installed at 39K, and they seemed to run better than the OEMs for me. The ECU was put back to stock when I sold it, and I sold the alfaworks ECU to another member on this forum. Only other "mod" is a BMC filter (and the touchscreen radio). If you have any other questions about the car's history, I'll be glad to tell you what I know, just send me a DM. I'm not on here a ton anymore since I don't own a 4C anymore, but I'll check in periodically.

Hey there! Thanks so much for responding. I went ahead and sent you a DM with some other questions that would be helpful.

 

[Flash]

I had two long splits in the boost hose from IC to turbo, and that didn't produce any codes.
(was a silicone hose, too!)

When that happened though, did the car lose boost? Did the boost gauge when in dynamic mode not top out at WOT?

Asking because the OP didn't mention any performance losses, just the sound.

 

[4Canada]

When that happened though, did the car lose boost? Did the boost gauge when in dynamic mode not top out at WOT?

Asking because the OP didn't mention any performance losses, just the sound.

Yes, but my sound was also louder.
The cuts in my hose were major, though.
That was the reason I asked earlier in this thread about the boost gauge.
I thought perhaps a loose clamp or something less dramatic in this case.

 

[jmoss]

Listening to that just makes to want to go for a drive.

Tracking down rattles in this car is lots of fun sound it is very stiff so sound travels nicely around, even harder to guess from a recording.

If it only does it under acceleration, then it could be when torque is applied engine twists and something is fouling.

I see you video with panels removed while they are off I'd recommend do this Alfa Romeo 4C / Guilietta 940 Lower Engine Mount Bushing Insert | PowerflexUSA

Take a look at your engine mounts and this thread Upper Engine Mount Deterioration at 17k miles | Alfa Romeo 4C Forums (4c-forums.com)

My engine mounts had failed so engine had heap of movement and I had similar noise under acceleration where the exhaust bracket would just touch the sway bar.

 

[CCCC]

So I pulled the bottom tray just to take a look. Everything looked ok for the most part. Although I did find a heat shield right under the turbo, on the catalytic converter, and it was fairly loose. Not sure if this is normal as I didn’t really see any way to tighten it? Here’s a video of it.

I say that is the culprit. I had similar issue with other car very similar in design. Heat shield. Try screwing or jamming a bolt and try it. i Bet it is only when under load being driven too and does not happen while high rev stationary.

 

[qwikrex]

Did some more testing over the weekend. Tried some octane booster as well as filling up with 103 octane unleaded race gas. No effect whatsoever. Boost seems to hold fine around 19-20 psi at peak according to my obd boost gauge. Doesn’t really change when noise is occurring. I’m starting to run out of ideas lol

 

[qwikrex]

Brought it to limitless motor works in Miami to take a look. They took a look inside combustion chamber with a camera and said they saw no signs of detonation. They also couldn’t find any loose boots/shields etc. At this point I’m not sure what else it could be. My only other theory is possibly the turbo wastegate rattling? I’m starting to loose hope lol. I ended up making an appt at an Alfa dealer Monday morning to see if they have any luck finding anything.

 

[Rabid Atoms]

Mine had that very same rattle. I had installed the kit that opened the trunk lid automatically and traced it back to a washer rattling against the metal brackets. My rattle sound exactly like that when I got on it. I removed the kit and the rattle went with it.

 

[Alfanut]

Brought it to limitless motor works in Miami to take a look. They took a look inside combustion chamber with a camera and said they saw no signs of detonation. They also couldn’t find any loose boots/shields etc. At this point I’m not sure what else it could be. My only other theory is possibly the turbo wastegate rattling? I’m starting to loose hope lol. I ended up making an appt at an Alfa dealer Monday morning to see if they have any luck finding anything.

There’s a turbo to intercooler pipe with some kind internal resonator inside it. That resonator has been known to detach itself internally. You might want to take a look in that area.
GMS - Turbo to Intercooler pipe

 

[jmoss]

Brought it to limitless motor works in Miami to take a look. They took a look inside combustion chamber with a camera and said they saw no signs of detonation. They also couldn’t find any loose boots/shields etc. At this point I’m not sure what else it could be. My only other theory is possibly the turbo wastegate rattling? I’m starting to loose hope lol. I ended up making an appt at an Alfa dealer Monday morning to see if they have any luck finding anything.

Ah I didn't realize you are in Miami. If you have no luck with Alfa, if you want to take me for a ride, I can lend an ear. I've fixed lots of rattles on mine might be able to find this one.

 

[4Canada]

There’s a turbo to intercooler pipe with some kind internal resonator inside it. That resonator has been known to detach itself internally. You might want to take a look in that area.
GMS - Turbo to Intercooler pipe

Brilliant idea, Alfanut!

For the OP:

It is on top of #1 on this diagram (not numbered).

This is what the part looks like. Besides the bracket being broken off (which in itself may cause your rattle), Rudi found that cylindrical part broken off inside.

This is what it looks like from under the car (front right of engine bay). GMS replacement piece installed.

 

[CCCC]

Brilliant idea, Alfanut!

For the OP:

It is on top of #1 on this diagram (not numbered).
View attachment 141004
This is what the part looks like. Besides the bracket being broken off (which in itself may cause your rattle), Rudi found that cylindrical part broken off inside.
View attachment 141005

This is what it looks like from under the car (front right of engine bay). GMS replacement piece installed.
View attachment 141007

Is this visually or by feel possible to detect from underneath ?

 

[4Canada]

Is this visually or by feel possible to detect from underneath ?

Have to remove the undertray to see this. From there, you can identify if the bracket is broken.
As for the interior piece, you might be able to tap it to hear a rattle. To remove it is two bolts but then you have to pull the hose off the other end - PITA. Only thing worse is putting this back on again!