Earlier i could not figure out why my friends mechanical temp. gauge was not working. His instrument voltage regulator went out and it's too much labor to get behind the printed circuit board so his dad put on those aftermarket temp gauges with sensor. Well, since his truck is japanese the manifold where he should put the sensor was way too small. You can't even use an adapter cause the actual sensor is bigger than the threading in the manifold. And so his dad made a T joint in the radiator hose. but he did not put the sensor towards the bottom to let gravity give it circulation across the sensor. The gauge would show absolutely NO temperature. When i turned the sensor upside down for him, sure enough, it reads temperatures fine now. How is it that the sensor won't read the boiling hot air right above the coolant at all. (does not go beyond zero at all) but has to Touch the coolant to get a reading? Is the sensor really that smart that it won't give you a reading unless it feels liquid? or is the air in the radiator hose alot cooler than the coolant? (the gauge starts at 100 degrees)
Coolant temp sensors are designed to measure the temp of a liquid, not a vapor. Why? Fuk Idunno. But it's a pretty classic scenerio when some dunderfik comes in w/ a blown headgasket or worse and says the gauge was reading hot and then the needle dropped down to operating temp again real quick like. Perhaps the density of a liqud better transfers it's heat to the guts of the switch better than a vapor does?
hey crew, the reason for this is simple. air is less dense then liquid therfor it will not transfer heat as well. you can stick your hand in a 200'C over to pull something out and it wont even feel warm. Stick your hand into a 200'C pot of water and you'll come out needing skin grafts. Therefor if they made the temp gauage sensitive enough to detect the tempeature of the air when it came into contact with a liquid it would go off the dial. Danny
ok, that makes sense. ( you both mentioned air versus liquid densities) they are definitely differrent enough so that the gauge could not be calibrated for both. I should of thought of this. now you know why i'm a history Major and not physics or science!!!!~
. ( you both mentioned air versus liquid densities) they are definitely differrent enough so that the gauge could not be calibrated for both. I should of thought of this. Motometers as used on Model A's and such are designed to work up top measuring warm fog rather than water...I think one would look great on a Japanese truck. Just cut a little hole in the hood over the radiator cap.
The Jalopy Journal
