One more strange noise when car is hot
 

Well I have the impression that all the strange things in the world concerning my car happen only to me !!!
Specially, problems that happen to my car are difficult to reproduce in order to point them to the mechanic and solve them out. This is because these problems occur under specific circumstances and not all the time.

So the problem goes like this:

When I have driven a lot in traffic in extremely hot weather conditions (very high temps here in Greece this time) I can hear a metallic loud noise that seems to come from the exhaust (metals touching each other) at 5000rpm. This metallic sound comes only when I am moving and reaching 5.000rpm and you cannot hear it if I am at complete stop and revving till 5.000rpm or more. The strange thing is that after I hear this sound and I try to reproduce it by accelerating in order to reach 5000rpm I am able to reproduce it 3-4 times but then after a while it stops !

It seems that when metals of the exhaust reach a certain temp then at 5.000rpm they produce this grinding noise but if you insist several times to reproduce the sound this noise is gone. When I hear this sound the car seems really hot, specially inside cabin.
However, if you again continue driving in traffic you are going to hear this sound. On the other hand, if I go out of the traffic and drive in a motorway the temps of the car seem to get lower and I hear NO grinding sound at all.


How in …I am going to figure out what this problem is????