2006 Corolla - strange rattling engine/exhaust noise when hot

[Adal9087]

Hi all,

I have just bought a second hand Corolla (2006, manual, 105k km) and have discovered a mysterious and annoying noise. As far as I know there are no other posts on this - apologies if so.

When the engine is cold everything sounds fine. After about half an hour of driving and the engine is hot I notice a soft, background whirring or high frequency rattling noise. It sounds like it is coming from the engine bay, possibly behind the engine block, but I can't be sure.

The noise is loudest when I hit the accelerator (while moving), and on lift-off (while still in gear). The noise stops when I push the clutch, and is more or less the same frequency throughout the rev range. I cannot hear the noise when I rev the engine.

At first I thought it was something in the engine, but I assume it is not as I can't hear it at idle or when I rev the engine at a stand still. I also thought it was a transmission issue, but given that the frequency does not change when the revs drop or when car slows down or when the clutch is pushed in, I assume it is not in the transmission.

The only thing I can think it may be is something in the exhaust expanding when hot and rattling.

Does anyone have any suggestions or ideas as to what this is, or where to look?

(I should say I have taken it back to the (small) dealer where I bought it - as the car is still under statutory warranty the dealer said he couldn't hear a thing - go figure).

Thanks in advance!

[jeffy]

could be an exhaust leak ?

[Adal9087]

could be an exhaust leak ?

Thanks @jeffy. What's the best way to diagnose this / eliminate it as a possibility?