What can cause an engine to become loud at 3000rpm

[kilou]

Hi,

my engine (290000km) has always been pretty loud but especially when it reaches 2800-3000rpm and above too but sometime a bit less than at 3000rpm. No real abnormal noise but it's just way too loud. I replaces the engine mounts and the exhaust system appears in good shape (anyway this loudness has been present for way over 150000km now so it is nothing new and I wonder if it wasn't already present on day 1!).

Do you have any hints on what to do to pinpoint the cause of that loud engine? Could it be an internal problem? I changed the intake manifold seal but it didn't change and anyway the sound doesn't appear like an intake leak. It's basically a normal engine noise but way too loud. Is it possible that the dampng material on the firewall became deteriorated that much? Is there anything to do to fix this?

Any help appreciated. thanks!

Thanks

 

[blackcherry06]

Knowing more about the vehicle would be a big help. Make / engine please.

 

[simple_gifts]

Any chances the accessories (alternator, water pump, AC compressor) could be the source of the noise.

Many mechanics use a medical stethoscope or length of hose to isolate noises.

You could also remove the serpentine belt or individual belts (for a short time) to determine if it is accessory related.

 

[javacontour]

Could be any of the previously mentioned items.

I'd also consider a leaking exhaust, checking that it's driveline and not engine noise, it could be a broken engine mount or exhaust hanger, exhaust heat shield, a defective air filter, and so on.

In other words, it could be any number of things.

 

[kilou]

Well the car is a 1997 Volvo S40 with a 2.0 petrol engine normally aspirated (not available in Norh America).

The noise is definitely not accessory related. I already tried to drive without the accessory belt and the noise is the same. The engine mounts have been changed recently and this didn't bring any improvement in noise levels. The air filter is new too as are the spark plugs. The noise is really not specific, it's just a normal engine noise that is just too loud in the cabin. I also thought about an exhaust leak but the engine runs fine until it reaches 2800-3000rpm.

 

[Anduril]

My engine always seems to distinctly change its sound as well as provide distinctly better acceleration right around its torque peak (3600 RPMs), but I've never thought anything of it. Almost feels and sounds like VTEC kicking in, but sadly, I don't have it.

 

[Gary Allan]

So, you can have the rpms hovering at 3000 and this noise is sustained? ..or is this under WOT/heavy throttle? In any gear?

 

[PandaBear]

Engine mount or exhaust leak that resonant at a particular rpm.

 

[Merkava_4]

Are you using Mobil 1 5W-30 ?

 

[moribundman]

Originally Posted By: Anduril
My engine always seems to distinctly change its sound as well as provide distinctly better acceleration right around its torque peak (3600 RPMs), but I've never thought anything of it. Almost feels and sounds like VTEC kicking in, but sadly, I don't have it.


Is this sound new or has it always been there?

Maybe your engine has a variable intake manifold. My engine's noise changes with RPM and it's due to the intake manifold. At a particular RPM range it's outright raspy, which is normal for this engine.

 

[badtlc]

I have a variable intake on my Mazda that opens up around 3000 RPMs. It makes the engine noticeably louder when giving it gas. Does your car have a variable intake?

 

[Quest]

Kilou-

3000rpm maybe your exhaust's tuned resonance point (peak) where the exhaust will sound the loudest.

Q.

 

[Anduril]

Originally Posted By: moribundman
Originally Posted By: Anduril
My engine always seems to distinctly change its sound as well as provide distinctly better acceleration right around its torque peak (3600 RPMs), but I've never thought anything of it. Almost feels and sounds like VTEC kicking in, but sadly, I don't have it.


Is this sound new or has it always been there?

Always been there. Just seems to have more "vroom" at those speeds.

 

[mechtech2]

Metallic or resonance?
You are at about your torque peak at 3,000 RPMs.
Intakes and exhausts have resonators and Helmholtz chambers to eliminate this type of noise on passenger cars.

But what is the noise exactly?

 

[PT1]

Originally Posted By: Merkava_4
Are you using Mobil 1 5W-30 ?

 

[kilou]

Originally Posted By: Quest
Kilou-

3000rpm maybe your exhaust's tuned resonance point (peak) where the exhaust will sound the loudest.

Q.


Is there a way to improve that?

 

[Kestas]

I'm with Mori. Your intake may be the dual-runner design.