In a message dated 96-11-12 14:53:34 EST, you write:
<< Though the temperature gauge on my 1974 Spitfire is operational, it seems
to be off calibration. When warm, the gauge never rises much above a point
about 1/4th of the way along its full scale. Seems to me that a ĒnormalĒ
indication would be at or slightly below the halfway point. Is this true?
And does anyone know if there is an easy way to check or Ēzero setĒ the
temperature gauge indicator?
Incidentally, while my car usually runs at an even temperature, idling on a
hot day does get that gauge heading up the scale rather quickly. Makes me
think I should find a way to replace the long-since-gone air deflection
panels between the radiator and grill.
Incidentally, my temperature sending unit IS new, leading me not to think of
it as a problem in this instance.
Martin Secrest >>
Martin,
Why don't you have someone hold a digital pyrometer to the thermostat housing
and use that reading to reference the gauge reading. (If you get a $2
thermistor from Radio Shack and connect the leads to a digital VOM you can
achieve the same results, only slower reading). The key here is to compare
the gauge reading to the actual temperature. Those "C-H" gauges were less
expensive and used because assembly line variances would mean calibrating a
real sender/gauge installation. In a Spitfire!? Yeah, right!
If the temps are indeed running low most of the time, then shooting up at hot
idle, you may be missing a thermostat. A proper thermostat actually slows the
flow of coolant so it has time to dissapate heat while passing through the
radiator. If the hot liquid flows too quickly, not enough heat can be
transferred. Take off the thermo housing, check for thermostat, then if it's
there, check for proper operation (as per the manual).
The fan shroud really doesn't do that much in a Spit. I've got two and
neither has those crappy shrouds, and neither overheats. Does your fan have a
viscous coupling or is it solid mount? A worn coupling that's slipping too
much will not draw enough air through the radiator--that's an overheating
problem at idle. With the engine off, try to spin the fan. If the blades go
around more than one full rotation, you probably have a coupling going bad.
If it's a solid mount, have you got the right fan?
The big thing is to make sure that the gauge is giving you an accurate
indication of what's happening in the engine bay. Don't start taking anything
apart until you know the gauge is matching what's actually happening. When
the gauge reads cold or hot, what's the actual temp at the thermo housing.
Good luck,
Charlie B.
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