172 cup scraping/grinding noise at high revs

[Oddesy]

Hi everyone, I've noticed a noise I can only describe as scraping or grinding when my car is under heavy load, it only does it when I take it above 4500-5000 revs is, so its when ever it comes into the power band. I held the car at at 5000ish revs and it continues to make the noise. My immediate thought was dephaser pulley/cam issue, although I had my belts and dephaser done 2k miles ago.

Can anyone thing of what else this could be or anything to try to help diagnose the problem?
Cheers!

 

[adamlstr]

Would you say it sounds like the exhaust is hitting the subframe?

 

[Oddesy]

Would that not be more of a knocking noise? It definitely sounds like a metal on metal grinding sound, and its only at high revs, lower revs it's fine

 

[adamlstr]

Standard engine mounts are made of chocolate, it's likely to be the exhaust hitting the subframe under heavy load as the engine twists with acceleration. I had it on my cup, it sounded horrendous. Like a knocking and a grinding all at once.

It's not limited to just high-revs though, it's more about load (full throttle for example); and would be worse in 1st/2nd gear.

Best mod I ever did to my Cup:
http://www.vibra-technics.co.uk/renault/clio_2_172_182

 

[Oddesy]

I've heard this before, that the engine mounts are't great. Is there any way I can diagnose this for sure before I splash out for new engine mounts?

 

[Ol’ Tarby]

You could always try loosening the top mount, pulling the engine as far forward as possible, and tighten it up again. That fixed the issue on my old 172

 

[N4TH4N]

I've had this for ages. Replaced all mounts. Made no difference. Dead annoying! Just cannot figure it out.

 

[adamlstr]

I've had this for ages. Replaced all mounts. Made no difference. Dead annoying! Just cannot figure it out.

I repeat:

Standard engine mounts are made of chocolate

 

[N4TH4N]

I repeat:

Replaced with solid engine mounts.

 

[adamlstr]

Replaced with solid engine mounts.

Lol, then something else is broken.

 

[N4TH4N]

Lol, then something else is broken.

Evidentially, but a complete mystery as to what!

 

[Oddesy]

So I had a bit of a play with my car on the way home from work. Tried bringing the revs up when the car was still and out of gear, it starts to make the noise at bang on 4000rpm. Also discovered that the noise starts at 4000rpm when driving, when giving it more revs this time it seemed to stop, and when I left off the throttle it makes the noise again when it hits 4000 revs again on the way back down.

Surely this isn't the exhaust on the subframe? More stumped than I was when I first heard it. Any more ideas?

Cheers!

 

[flebay]

possibly broken cat internals

 

[Oddesy]

Think you could be right flebay, did a bit of investigating at the weekend, the noise cant be heard in the engine bay, but stuck my head under the car and sounds like its coming from the cat

 

[chris-foci]

Heat shield rattling?

 

[steve_b9]

I had this for months. Replaced aload of stuff.
In the end i got someone to rev it for me while on the ramp.
Found that one of the springs on the manifold to cat joint on the exhaust had snapped. And the bolt was just hanging down rattling on the exhaust.