[mac2000]

I've noticed a slight rattling from the engine bay of my 2000 when the engine drops in revs from startup. I'm assuming the rattling starts when the engine begins to vibrate more at lower idle speeds. I haven't been able to get it on a lift for inspection but was wondering if anyone had a similar issue. I'm wondering if it might be the A/C compressor clutch housing? The A/C works fine but the rattling does not go away when A/C is turned on.

 

[maxvelocity]

Go for the easy items 1st such a heat shielding or loose sheet metal parts. Like exhaust or cat parts.

 

[ksgrimsr]

Go for the easy items 1st such a heat shielding or loose sheet metal parts. Like exhaust or cat parts.

I had a rattle at lower RPMs on my V8 for a while right around 2000 RPM, and it was the bottom lip of the rear diffuser vibrating against the rolled lip of the muffler. Loosening the muffler clamps a bit and shifting it slightly to increase the clearance helped. I ultimately also stiffened the lower lip of the rear diffuser near the center (I have a late model center exhaust) since the diffuser was awfully floppy. Stiffening just entailed a piece of metal rod placed in the lower lip of the diffuser and secured with a couple dabs of sealant. In my case it was easy to see that this was the culprit because of the wear mark the diffuser lip and muffler lip were making against each other.

Knut

 

[Zippy_Slug]

Meh.. mine does that too.. I suspect it's some heat shielding or exhaust pieces.. It only does that at idle ~950RPM and it's not at idle very often..

so I chalk it up to :tadts:

 

[carbuff]

The OE V8 side-tip exhausts were prone to breaking (and would rattle when that happened).

So, yeah, :tadts:

 

[mac2000]

Thanks for the suggestions. I have the retro-fitted JAE center exhaust with straight pipes. I'll look to see if there's a diffuser or shield near the pipes although I don't recall seeing one when I replaced the injectors. The noise sounds more like a loose washer.

 

[jtrealty]

The OE V8 side-tip exhausts were prone to breaking (and would rattle when that happened).

So, yeah, :tadts:

VERY common for the tailpipes to crack on the earlier side exhaust. I don't know about the center exhaust type but certainly something to check. The good news is they can be welded.
David Teitelbaum

 

[OnAir]

Meh.. mine does that too.. I suspect it's some heat shielding or exhaust pieces.. It only does that at idle ~950RPM and it's not at idle very often..

so I chalk it up to :tadts:

Yeah, same here. Had to re-weld a bracket on my centre exhaust tips. The rattling drove me nuts! There's still a heat shield somewhere that resonates at around 1000 rpm, but the exhaust noise helps to mask it.

 

[mac2000]

Spoke with the guys at a local performance shop. They think the noise is coming from up front and is possibly a cam tensioner pulley.....worn bearings.

 

[MidLifeZ]

Spoke with the guys at a local performance shop. They think the noise is coming from up front and is possibly a cam tensioner pulley.....worn bearings.

if that is the case DO NOT DRIVE IT!

 

[gmendoza]

Have you checked your exhaust manifold heat shields? Strum them and you will know. If so, sometimes a larger washer can act as a temp repair.

If it is a tensioner, it could also be your serpentine belt tensioner.

 

[lotusdriver2001]

If it's reproducable then get a vacuum cleaner hose and use it to listen around. Careful of them moving parts but you can crudely "direct" your hearing. Lots of echoes in the V8 engine area.

 

[mac2000]

I didn't know there was a heat shield near the manifolds. I'll check them out. Like the vacuum cleaner hose idea too. Will keep you updated. Thanks.

 

[mac2000]

Used a remote scope to inspect and found a missing RH rear exhaust manifold stud and nut missing. No leaks from visual. There's a metal strip that acts as a washer and locking mechanism and I'm going to check to see if this could be the source of the noise. It looks like it would vibrate against the header to generate the type of noise I'm hearing. I'll hold scope there with engine running to test.

 

[lotus4s]

check manifold heat shields and motor mount heat shields, notorious for noise...

 

[gmendoza]

Missing exhaust manifold studs are common. While not good, there are usually not the cause of rattle unless the locking strip is vibrating against something.

I'd still check the manifold heat shields like Jim said.

 

[Wayne Ellison]

Another rattle source which is hard to trace is the A/C compressor's three small arms that couple the drive to the center shaft. They will rattle at 1800 to 2000 rpm, only. drove me crazy till I found the source.

 

[mac2000]

I finally got the car up on a lift and still could not find the source of the rattle. It's not that noticeable but there. The only heat shield I noticed was a molded silvery material mounted to the sides of the engine bay but didn't see any nuts or bolts holding it in place. Could it be engine noise?

Wayne, if the source is the a/c's 3 arms wouldn't the noise stop when the clutch is engaged...i.e. when a/c turned on?

 

[gmendoza]

I think you missed the heatshields. They are bolted to the exhaust manifolds. See pic:

 

[mac2000]

Thanks for the pics! I didn't see them earlier but using the scope, the nuts seem to be on securely. I bought a 1.5" dia. plastic flex tube from HD and i'll try to pin point the source that way.