Armchair diagnosis

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Just after bouncing some ideas off others here before I get stuck pulling my car apart this weekend.

I've got an issue at the moment that is puzzling me with my '99 Mx5. I'm getting an annoying squeaking sound that increases with intensity with RPM that sounds very similar to when the wear bar on brake pads start to lightly rub the disk.

Oil levels and quality look good (only 4k since last change with Mobil 1).

The noise remains even when still left in gear, but clutch pushed in.... but the sound dimishes when the clutch is pushed in (so I'm fairly confident its the engine side of the driveline as the squeak correlates to the rpm of the motor).

If I shift the car into neutral and rev the motor the sound persists.

Sooo... what I'm left with is bearings, something is up with the flywheel or input shaft on the gearbox, or maybe even just a belt (even though it sounds a little too metallic to be a belt). I'm also told a loose manifold can give a noise similar to what I describe, and it recently had the exhaust done (full new cat back job) so I was going to check that too.

Any advice before I poke around and/or take it down to my mechanic?

[kazjim]

Clutch Throwout bearing ?

[GP]

+1

[ampz]

Check the lower mounting bolt on your alternator.
Make sure it's tight (or even there)
I'm surprised it didn't die, but then again, it's not the original one and I don't really know where it came from but it ain't broke...

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Cheers for that suggestion about the alternator. I'll have a look at that as well.

[Charlie Brown]

Clutch Throwout bearing ?

+ another 1.

Can't be the alternator as pushing the clutch in doesn't effect any belts/bearing in that area.

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Ok, more diagnosis today helping me pinpoint it.

I wasn't feeling crash hot so stayed home and put the front end up on ramps. I pulled the entire exhaust off (bar the headers) and there was no chance to the noise (well, the noise in question).

It's since got a little louder and more consistant, and now definitely reduces in volume significantly (to the point where it almost can't be heard) when the clutch is depressed. It also sounds loudest around 2,500rpm under load.

So yeah, time to take it to a gearbox joint I think

[JBT]

Try MX-5 Plus

[Jace]

the previous owner of my car (who happens to be a relative) informed me that the gearbox responds very negatively to increased idling in gear with the clutch depressed (sitting in first at lights, rather than in neutral).
my car in particular has had approximately $3000 spent on the gearbox (two owners ago) to correct the clutch throw bearings.
good luck getting this sorted.

[orx626]

It's since got a little louder and more consistant, and now definitely reduces in volume significantly (to the point where it almost can't be heard) when the clutch is depressed. It also sounds loudest around 2,500rpm under load.

Trevor, it might be worth checking the oil level or even replacing the oil, and see what results.

Regards,
Danny