Help - Apocalyptic clattering / banging noise

[apk]

'94 SW20 turbo widebody.
I was just driving home (5 or 6 km into the trip) when suddenly (at low speed) I get a world-ending clattering noise coming from behind my seat - it sounded like someone had tied a tin can to my driveshaft.
I stopped - as you do - to look under the car. I figured I'd picked up some garbage off the road, but nothing wrong. Nothing loose, nothing hanging down, no damage anywhere?
Took off again, same thing. Clatter a bit when I rev the engine stationary, but not much. Try moving and all hell breaks loose.
Eventually I realized that under acceleration all is quiet but as soon as I back off........ WW3
So I figured exhaust baffle?
I've got a twin muffler set up - Jasma branded - but they look like resonators, not mufflers so I didn't think they had baffles?
I decided to keep going & the same clatter - silent - clatter went on for about 10k then suddenly all silence. (regular MR2 noises, not complete silence)
Everything about the car except the noise was normal.
Clutch OK, Oil pressure, temperature, boost all OK.
Anyone have any ideas what it could be?

[Ryan S]

i had a similar thing happen (i'm not saying this is your problem). it turned out my intercooler shroud brackets had broken and the shroud was walloping about all over the place

[apk]

Thanks Sheppy,
I just took a look (flashlight as night has fallen over here) & can't see / feel anything loose - but 'walloping about' is a beautifully accurate phrase that I'll plagiarize tomorrow when I take it to a workshop & put it on a hoist...
(how to translate that into Thai? Anybody?)

[Ryan S]

Thanks Sheppy,
I just took a look (flashlight as night has fallen over here) & can't see / feel anything loose - but 'walloping about' is a beautifully accurate phrase that I'll plagiarize tomorrow when I take it to a workshop & put it on a hoist...
(how to translate that into Thai? Anybody?)

"moving around erratically"

ย้ายรอบผิดพลาด
Ŷāy rxb p̄hid phlād

[Ryan S]

it is strange that it only happens on overrun, it certainly sounds like something has come loose, does the car feel ok to drive?? it's not suspension components or anything??

[apk]

It feels absolutely normal.
The only thing I noticed when I looked just now was the throttle cable that clips onto the intercooler piping had come out of it's clip - hardly what I was expecting to see (alternator dangling by a wire?)

Thanks for the Thai translation BTW.

[Ryan S]

Deffo sounds like something in the engine bay, try revving it while looking in the bay.

Honestly mate, the noise my broken shroud made was awful, sounded like i was dragging a marching band behind me!!

[rev3gtturbo]

When I have had weird noises like this it has been heatshields, undertrays, or a broken induction kit support bracket.

[apk]

I had a thorough look at all the shields & support brackets around the intercooler this morning & there is nothing loose (or missing).
Then I got to thinking - what if there is something rattling around INSIDE the intercooler? Would explain how it rattles on overrun - negative pressure flaps it around & positive pressure pins it in one place?
That may also explain how the throttle cable came unclipped from the induction pipe. (vibration)
The question is: What could possibly break off inside an intercooler?
Is there any little deflectors or baffles inside that could come loose?
I've no time to pull it apart until the weekend now. Is there anyone out there who knows what lurks inside an original turbo intercooler?

[Draven]

Check your turbo?? make sure you've not lost part of your turbo into the IC...

[GreddyMR2]

I had similar problem.

When I accelerated, it was silent, but when released the accelerator, sound was like banging. And it was related with a speed. The problem was loose driveshaft.
Ahh but when you hear this sound when revving, that's something different

[apk]

The other thing to note is the sound has (for now) gone away again.

I don't think it's a disintegrating turbo - I still get full boost & most of the bits that can fall off on of those are, well, fairly important!

I have a friend who is a race car engineer & he thinks a deflector may well be added inside the IC to reduce blow-back to the turbo & failed one would produce my symptoms. He also warned that if that is indeed the case then little chewed bits of aluminium sucked into the engine might not be a good thing....

Has nobody here had a look inside their IC lately?

[nickg07]

Hm im no pro, but shafts, LSD?, gearbox bolt onto engine mount?

[apk]

Well, Greddy turned out to be right on the money!
The RHS driveshaft bearing has destroyed itself, but the issue was disguised by a second issue with a broken exhaust support bracket (where it passes over the crossmember) which was making stereo banging & knocking noises.

Thanks for all your help guys.

[Ryan S]

glad you sussed it out mate