did you replace the timing belt on it? the belt should be replaced at 100,000 miles and then every 75,000 after that.
locations for possible coolant leaks are the lower intake manifold gaskets or the heater core lines that come from the lower intake manifold.
another issue these engines have is an oil leak from the oil pump drive shaft and its located just under the TB. it is very expensive to have fixed professionally but if you ever have problems clean it and JB weld it shut.
the alternator is a PITA to replace. and most mech's that look at the engine treat it like lost wreckage from Roswell!!!
all that being said i love the engine I got 214,000 miles out of my 96 DOHC and only swapped to the 3800 because of the availability of replacement and performance parts
