Topic: Temperature gauge in my 40


wmgmitchell    -- 06-12-2012 @ 4:52 PM
  When the temperature is between 70 and 80, the gauge in my 40 is usually in the middle to 3/4 position. My question is: approximately what is the temperature when the gauge reads halfway and about 3/4?

I've never had the car boil over but I do get concerned when the needle approaches the hot line.

Much obliged!

Bill


supereal    -- 06-12-2012 @ 7:37 PM
  The best, and only way, to correlate the gauge and the actual coolant temperature is to put a thermometer into the coolant. That said, be very cautious about removing the radiator cap on a hot engine. Cover the cap with a big rag and remove it very slowly. Some prefer to use an infrared temp gun, but they seldom give the correct reading as they are moved around. If your radiator isn't boiling in summer weather, you don't have a problem. Gauges in old cars are not precision instruments, and shouldn't be viewed (no pun) as such. The King-Seely system is kind of like a weather vane. It tells you the direction, but not the velocity. Before they arrived, most of us used "Moto-meters" which mounted in place of the radiator cap and had an actual thermometer in it. They were not precision instruments, either, but when the red line hit the top, the water jug came out of the trunk.


TomO    -- 06-13-2012 @ 7:43 AM
  At halfway the gauge reads somewhere around 160 and at 3/4 the gauge is around 180.

Calcium deposits and age affect the accuracy of the temp gauge, but the King Seeley gauges are more accurate than the balanced resistance units used by other manufacturers.

Unless the radiator is loosing coolant, I would not worry about the gauge reaching the top limit for short periods of time.

Tom


supereal    -- 06-13-2012 @ 12:05 PM
  The rating of the thermostats, if you are running them, will establish a "normal" reading. The usual choice is 160 or 180 degrees. We recommend the lower level. With the Ford two sender system, the one with two terminals is just a thermostatic switch that opens at or near the boiling point, causing the gauge to peg on the "hot" side. The single terminal sender relies on a heated bimetal switch that vibrates as the coolant temperature changes, to "bias" the switch. The power is furnished by the gauge circuit. It is important that the single terminal sender body have a good connection to the cast iron head. The mount is a pipe thread, and a minimum amount to sealer is necessary, and no Teflon tape should be applied.


wmgmitchell    -- 06-13-2012 @ 6:33 PM
  Thanks very much, fellas. I'm real impressed with the depth of your knowledge and I appreciate the education!

Bill


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