There is no 2015 Mitsubishi Montero. A 2005 Montero does not have a four cylinder engine either. So my information may be wrong, as I guessed that you had a 2005 Montero with a V6 engine (the only engine available).
I am betting that the sound you are hearing is like a combination of a roaring and whooshing sound. Probably your cooling fan clutch is slipping a little bit.
With the engine off and cold, turn the cooling fan by hand. It should have some resistance, but still turn. If it turns freely or lightly, then the clutch has failed and needs replacing. Check it and let us know.
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Tuesday, July 25th, 2017 AT 3:57 AM