I recently did an acid flush and the car was running fine until a few
days after the flush. The car now is running hotter than *before* the
flush.
Cooling systems are difficult to diagnose. You need a thermometer, I
use the infrared contact-less type. First make sure the gauge is right.
(It probably is, but that's where you start.) Measure the head
temperature
where the sender is. Then you check the temperature of the hose exiting
the radiator (bottom). It should not be hugely cooler than the other
one, or it indicates that flow is compromised. Feel the radiator
surface
to see what its temperature gradient is.
Water pumps fail in one of two ways. Either they leak (common), or
they stop pumping well (uncommon). Bearings can fail, but that is
usually closely associated with leaking.
The fan clutch is difficult to diagnose, as it won't engage if the
radiator is not doing its job. It's the hot air coming through the
radiator that makes it grab, so lots of other problems can take it
out of the picture too. That fan is of little use at freeway speeds,
so if you're overheating there look elsewhere first.
All that said, I'd start with the thermostat! You did remember to
put it back in after the flush, right? Is it in correctly?
-- Jim
