[Bru]

Check the coolant level to be sure that its not low in the radiator and that the overflow tank functions normally. That is, the level increases slightly when it's warm and then gets drawn back when it's cold. There are high and low cold lines on the tank. Does the radiator still have the plastic fan shroud or is that missing? It would be more necessary for cooling at low engine speeds than high. There's even a small section that clips on to the bottom that took me years to find. Sometimes air can get trapped in the system. The way to burp it is to run the engine on an incline with the front high and the heater on. The classic sign of a bad head gasket is after running the engine that you get a lot of gurgling from the overflow tank that can overflow coolant onto the ground. Be sure you're using at least 50/50 antifreeze /distilled water or a premix of the same type. Check the fan clutch when it's cold by pushing on one of the blades with a little force. It shouldn't turn more than 1/4 of a turn. When the engine is warmed up and you rev it, the fan speed should increase with the speed of the engine. It might not be a bad idea to check the function of the thermostat by putting it in hot water or replace it. The jiggle valve goes up and don't over tighten the two retaining bolts. They strip easily. I use a small amount silicone on the flange. Check the tension on the fan belt. It also runs the alternator. When it's loose, it usually squeals on startup. Does your auxiliary fan kick in when it's hot? The only other weirdness I can think of is you may have an aftermarket water pump with stamped steel impeller blades that have rusted off. The OEM water pump should have AISIN cast into it on the front. That one has a cast-iron heavy-duty impeller.