I have a 1991 Grand Wagoneer that began running very hot after a recent alternator change. All belts are tight and water pump is workign fine (replaced 6 months ago), and thermostat is new and tested before installation. Mechanic says cause is some kind of clog in the engine block that is preventing coolant form getting to the top of the engine (and therefore never reaches thermistat or circulates past that back into the radiator. Two questions: (1) what can be done to unclog the engine cooling channels (absent pullign engine apart) and (2) is the timing just coinicdental relative tot he alternator change or is there some connection I haven't imagined. This is my second GW and I also own a '79 International Scott II, so am fairly familiar with the mechanics of non-electronic autos.