1998 Chevy Monte Carlo help please

Ok my father currently drives my car to work, and it is leaking coolant. He says its not leaking from any hoses or the radiatior. When I drive this car it will idle pretty low, ususally around 700-900 which is low for this car. The breaks stiffen up pretty hard and I can barely tap them and lock them up. If I am on a deciently long trip like 5 or more miles and or depending on how hard its driven it will smell like the engine or coolant is burning, and lasty when im cruising and just let off the breaks it immediatley decreases speed rapidly without hitting the breaks.
could the coolant be leaking into the one of the headgaskets or manifold. Could anyone please help me, thanks.