gong randomly sounding + new rattle at exactly 2k

[BulletHellDemon]

hey guys, first post here but i've been lurking the forums using the search function quite a bit since i got my first bmw in 2013. been meaning to join for a while to learn more about e30s but with this problem i'm having that's got me stumped i figured why not join up now lol.

so a couple days ago my e30 began doing this thing where the gong randomly sounds around 2 to 10 times for seemingly no reason at all. the car drives no differently than it ever has (besides one thing i will mention in a moment, but doesn't seem relevant), nothing feels weird, no lights in my check panel or dash are on. upon driving it today i realized that it seems to happen only when i'm accelerating to get up to the speed of about 45 mph, so it happens a lot during city driving. on the freeway however, it doesn't really happen so much at all. i'd say that even past about 40 or 50 mph or so it stops happening. one interesting thing is sometimes it'll happen when the key isnt in the ignition at all, but not like the car normally would gong if that makes sense. my guess is maybe a ground somewhere that has to do with the gong thing (frankly have no idea what that thing is) is loose or something and that maybe it makes contact (or doesnt?) under certain situations. really not sure where to start with this one at all.

also, my SI batteries are definitely in need of replacement and i'll be doing that soon once i pop my cluster out to see which type of battery i'll need. not sure if that's relevant.

on the same day this happened though, the car started to make a rattling noise at exactly 2000 rpm. i can't really tell where the sound is coming from, and it either sounds metallic or like a piece of plastic trim, i can't tell which though frankly. its almost like putting a pokemon card on your bike tire as a kid with a clothespin to make that "cool muffler" sound when the card hits the tire treads. my guess is maybe its an exhaust hanger or something that came unfastened and only resonates at the particular frequency 2k rpm creates. because once im at about 5150-5200 rpm it stops completely. i will say though that i can't tell exactly where on the car i think it's coming from, but my previous theory just makes the most sense in my head. it seems like it's more prone to happening most in first gear (i have an auto) but i can't be exactly sure. additionally, it only happens under load, i can't replicate it in neutral or park.

edit: forgot to mention that i've read something that said this may mean that the timing belt tensioner is about to crap out and the car shouldn't be driven anymore until it is replaced. is this true?

i don't think these two issues are related at all but it is curious that both started on the same day. does anyone have any idea where i should start looking with either of these issues? i haven't yet had a chance to look under the car to see if anything is loose under there like i think there may be but i will be tomorrow and just wanted to have some new insight when i jack it up and start looking.

sorry to be so long-winded, just wanted to be exhaustive in giving as much info as i could! thanks in advance for any help or kind words of encouragement!

[msservices]

To me it reminds me of when my exhaust shroud/shield was loose around the front of the system, i was about to tap on it with a small hammer to replicate the sound, (which as you know is hard to do), then I was able to cinch it tighter by wrapping a long hose clamp around the shroud/shield and tightening it down while shaping it to conform to the oval shape.

[sienayr]

I don't know this for sure, but the OBC may have a speed limit set, and every time you go over the speed limit the gong sounds.

[BulletHellDemon]

I don't know this for sure, but the OBC may have a speed limit set, and every time you go over the speed limit the gong sounds.

how would i change that? i have a 6 button obc and i thought that was only a function for the 13 button. i'm guessing it has something to do with the memo button since i have no idea what that one does. although i guess i could just disconnect the car battery to reset it and see if that gets rid of it.

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To me it reminds me of when my exhaust shroud/shield was loose around the front of the system, i was about to tap on it with a small hammer to replicate the sound, (which as you know is hard to do), then I was able to cinch it tighter by wrapping a long hose clamp around the shroud/shield and tightening it down while shaping it to conform to the oval shape.

good idea, i'll definitely take a look at that. you're talking about the heat shielding that covers the transmission but leaves the actual exhaust exposed right?

[msservices]

DC2249A0-904C-49B5-AA48-69C4A552BD30.jpg

[BulletHellDemon]

so my exhaust didn't have any type of shroud or fastener like that. everything under the car seemed totally fine. however while i was under there i saw (and suddenly remembered about) the hole rusting in my exhaust. it's the only rust i've been able to find anywhere on the car so i never really worried about it and i kinda forgot about it but it's been there since i've had the car. i've never had this rattling issue before though so i'm gonna assume that maybe that got a little worse and something that has to do with that is rattling. i was planning on putting a new magnaflow muffler on at some point kinda soon anyway. so hopefully that takes care of it.


also i disconnected the battery and on the short test drive i took it on the gong didn't sound so hopefully resetting the obc took care of it. i'll drive the car again tomorrow and report back on if it still freaks out on me.