Hi,

I own a 2005 Dodge Grand Caravan SXT / 3.8L

Last fall I've noticed some strange noise:
- it is a blowing sound (like a pressurized air escaping from
somewhere)
- I can clearly hear it only from inside, with all windows closed
(i.e. when no outside noise is heard)
- it cannot be heard under the hood or from outside / probably because
other engine noises are masking it
- it apparently comes from where the hood release lever / parking
break release lever are located, but noise source is somewhere deeper
- noise changes with engine revs not only when I step on gas, but also
when I'm driving down the hill on an "L" gear, which makes revs go up
without touching the pedals

It did not lead to any problems, and my mechanic did not find anything
suspicious, so I left it as is (again, _since_last_fall_)

Now when summer weather finally came and it is very hot outdoors,
there is a significant detonation in the engine; the hotter it is
outside the more heavy detonation is, beginning from about 23..24
degrees Centigrade.

I know that one of the reasons for detonation is overheating in
combustion chamber; another is lean mixture (which in turn can be
caused by excessive air being sucked inside). Engine itself is not
overheating; at least temperature gauge shows the same temperature as
it did last summer, when everything was Ok in hot days.

Taking into account that strange noise that started last fall, I
suppose that the symptoms are interconnected, provided that since last
fall there were no hot days before summer.

My mechanic did his best with combustion chamber cleaner, injectors
cleaner etc. etc; When a "check engine" lamp turned on I had to
replace the faulty EGR valve - I was sure at that time that this valve
was the main reason for the detonation, but I was absolutely wrong -
nothing changed except the "check engine" lamp went off.

* * * * *

If anybody have ANY ideas how to diagnose/eliminate the problem, I'd
highly appreciate it.
Or maybe just point me to the community/forum where the issue can be
further discussed.

Thanks !!