[jasmine]

I have a 1998 SQ420 Grand Vitara J20A.

For the last 2 months or so I've had a very loud metallic buzzing/rattling sound coming from under the car at exactly 2000 RPM, and then it goes away as the revs increase. It will happen both in neutral and out on the road. I'm guessing it is either something to do with the exhaust, or (heaven forbid); the clutch plate assembly somewhere. It does have a bit of a dodgy clutch - I've adjusted the clutch all the way because it would crunch a couple of times a day, especially going into 4th gear.
As for the exhaust, it has tin covers over the front muffler (cat?) and also between there and the manifold. There was a cover on the manifold but I took it off to see if it was that. It wasn't that unfortunately. The remaining tin covers are held on by corroded bolts, but the covers appeared secure.

Hmmm.

Any ideas?

[Lokidog]

I had a rattle metallic vibration coming from underneath. It's frequency and occurrence changed with engine revs. I had suspicions it was the muffler but I wasn't quite sure. Left it over night and reassessed the noise the following day. No exhaust shielding on the Zook so I could strike that off the list and the only thing left was the muffler. $165 and 1 hour later no more noise.

[jasmine]

Thanks Lokidog, I think you're right. I've since removed the shielding from under the cat (there is still a shield on top, but I see no reason for it to cause the big ruckus) and there is still that familiar buzz...

Was your replacement muffler a catalytic converter? I'm a student at the moment and have practically no money, so I will be either putting up with the buzz lightyear arrangement or going for a cheap and nasty alternative. I emailed the RTA technical gurus, and they say that as long as the new cat is of the same standard as the original, I can use a 'universal' one instead of the genuine Suzuki memorabilia.

Any ideas for an ultra cheap option? a straight-through pipe is not really preferable unfortunately

[Lokidog]

Mine was the Muffler at the rear. I have no idea what the Cat Converter at the front would cost to replace. I'd imagine an aftermarket/universal Cat would be cheaper than genuine Suzuki gear and would pretty much do the same job. It would be an idea to see if you can have someone determine if it is the Cat or the muffler.

[fordem]

Be interesting to know where you adjusted the clutch - AFAIK the only adjustment is the pedal free play, and that is best left alone.

The rattle you're hearing is almost certainly exhaust related, and most likely one of the tin shields - my SQ420 has no cat, but it have a tin shield under the first muffler, which has a very slight buzz - it had a rattle because of a cracked weld - I just pried the corner nearest the weld away from the muffler - try taking a ball-peen hammer and "dinging" the shield near one of the welds, all you need to do is change the resonant frequency slightly

[jasmine]

Thanks Fordem
You're right about the clutch. I was just adjusting the pedal so that it had less free-play and also sits a bit further out from the floor.
I've removed the bottom shield from the first muffler, and i've also spaced out one end of the top shield by placing a large nut in between the shield and the muffler at one of the bolt holes and tightening it back up. The noise is still there, so there could indeed be a crack up there somewhere. I might remove the muffler so I can get a proper look at the top side of it.