odonnell

It sounds like a metal scratching noise, only happens at ~2800 rpm. In gear, in neutral, or with the clutch in. There is no similar noise whatsoever at other rpm's. It happens upshifting, coasting, engine braking, etc. Basically it doesn't matter, if it's at 2800 rpm it scratches.

Any ideas of what it may be? I just had everything apart up to the flywheel so maybe it's clutch assembly related. I used the torque specs and it shifts fine. Could it be really abrupt exhaust or drivetrain resonance?

odurandina

drive the f_ck out of it.

if it blows up, pick up an frs to hold you over til the v8.

odonnell

I plan on driving it regardless, it doesn't seem like something is about to fail.

A v8 sounds great, but to be honest with you...the MegaSquirt conversion makes the 2.5 a more welcome guest and I'm actually in no rush to replace it. A few months ago my attitude was different. This conversion relieves all the burdens of Bosch/Motronic and the associated hardware for 1/5 - 1/10 the cost of a v8 swap. /end cheerleading

fiily

Sounds like rollers/tensioners are starting to go. When did you replace them?

fiily

That is what a mechanic told me about my 951, lol. If it blows up, time for some serious mods!

mel_t_vin

Sitting still?

Do you have all/intact exhaust hangars? Sounds [no pun intended] like you may be hitting a vibration harmonic in the exhaust. OE 30-yo cat? Parts of the ceramic have crumbled and the metallic substrate is vibrating against the convertor?

Get under the car, have someone hold 2800, and listen for said screeching.

konakat

Make sure one of the belts isn't rubbing. Somebody had a picture a while ago where their timing belt was only half its original width because of a protrusion on their belt cover.

odonnell

Thanks for the pointers guys. Right now It sounds like the heat shield above the cat could be it, thankfully. I actually don't have a cat, it's a resonator welded in place of it.

As for the belts, I verified today that the timing belt (have no balance shafts) is healthy and properly tensioned. It's about 3 years old, and so are the rollers. Plan is to replace them all in the winter just because, along with water pump and FOES.

odonnell

Still haven't worked out the noise, I've been driving it nearly every day and it's 100% repeatable. I got the car in the air and all exhaust hangers and heat shields are intact, but I'm 80% sure it's exhaust related, but there's always a possibility it could be something more important like a drivetrain part on the way out or (less likely) ignition predetonation, as I am running a DIY tuned map for that and I have no knock sensor. I made a video of the noise if anyone recognizes it.

Karl_W944

This is the bloody noise I was talking about months ago!!

I know it's not belts or rollers because it was still making that noise after I changed out my belts and rollers in April. Scratching/grinding noise just below 3000rpm(although I'm pretty sure mine has a bigger rpm range for that noise), on acceleration and deceleration in gear(but never in neutral), and when the car is warm.

My guess was very worn and playful wheel bearings. Mine are worn out and I haven't had the time to put new ones in.

Lemme try and get a video of it.

odonnell

I'm 100% sure it isn't wheel bearings in my case, it happens at all speeds including 0 mph. Which makes me believe it's exhaust related, or from something forward of the pressure plate because it happens whether the clutch is in or out.

Karl_W944

After my short drive, I'm inclined to agree with you as I noticed the sound went away when I depressed the clutch, and would reappear at those rpms when I let out the clutch while moving...

Here's my video:

konakat

Could be torque tube bearings.

Karl_W944

That sounds like something not fun to work on.

CliveB

Not sure if this applies but my '86 turbo had what was a commom problem where the exhaust manifold had cracked at a bracing plate underneath the manifold. Had exactly the same symptoms. It was a known problem and I managed to get the dealer to change it for a re-designed version as warranty work.