Thanks for the answers. It runs normally otherwise, the sound is not that loud and can only be heard when the window is rolled down. I had a person pressing the brake while looking in the engine compartment, and the sound comes from the drivers side like you said. It is around the AC compressor to be specific. Is the bower booster sitting on the frame or on the engine? Is it the black thing on the frame behind the driver side headlight?
I'll try to find the leaking hose tomorrow. By the way, am I looking for a hose or a metal pipe?
Thanks!

Karl
1989 Mitsubishi Montero 2.6, 2 dr, 5spd.
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