heres some more wacky thoughts then,

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if the gasket that was changed on the exhaust was the head to manifold gasket then hot gasses leaking at the number 1 stud could have damaged the alternator diodes, this has cooked the alternator as it vents/cools at the back, this voltage fluctuation/fault is being picked up on the low coolant alarm and they can be quite voltage sensitive.
the wire for the normal bongo temp sensor goes from the harness at the side of the alternator then goes over the front of the rocker cover to the sensor, this is again in the same area so could have been heat damaged, or the wire pulled breaking the top of the temp sensor itself, check it to see if the sensor top is wobbly and loose at the top. or again the sensor supply voltage is being affected by the dicky alternator.
first step is check the voltage of the alternator when ticking over after starting it up, then check again when revving then again when lots of accessories are put on, you may find its kaput.
wacky enough for you mike??????
