How many have actually looked at their motometer? There are four operating ranges indicated near the small circle. Operating temperature for for water pump cars, "Summer Average," for thermo syphon cars, and steam. From the motometer, it would appear that it is safe to operate the engine at 200 degrees Fahrenheit, once the temperature reached 212 degrees F, or steam, there is over heating.
From the motometer as a sensor of engine operating parameters, a water pump would, all things being equal, allow the engine to operate cooler. While operating with a thermo syphon, the object is to stay below steam.
FOOTNOTE: Not all Motometer faces are the same. The one that I am referring to is from a 1927 Willys Knight. A quick review of those available may just show "summer average" or operating temperature and steam.
I only look to see if it gets much higher than what normal is for my car. I have them on my A models as well but they run about 1/4th way up the gauge on hot days. Tim
I don't have a Motometer on my car - as Jay Leno said in his now-deleted Model T video, "sometimes ignorance is bliss - either it's running, or it's not!"
I bought one at an auction for what seemed like a fair price, since the red stuff (I want to call it mercury although I know it's some kind of alcohol solution) had all migrated to the top of the thermometer. Basically it looked like it was about to boil over all the time. Turns out it had been improperly handled and basically the contents of the thermometer had switched places. Gently bouncing the bulb, which protrudes inside the cap and towards the coolant in the tank, against a tire repeatedly will work it back into its proper location. I did just such an operation and now it's like new. I've had my radiator boiled out, and it's very rare that the red stuff ventures very far into the circle.
Jay Leno actually had a motometer on his car. At least it was there from what I remember about his video, and from when I toured his collection.
I use a moto meter on new engines. Once the engine is tuned up and broken in the temperature never gets high enough to worry about. Then the moto meter goes in a box on the shelf.
I had them on all three T's, but on one the car got very hot and the red stuff went all the way to the top. I tried banging it on a tire, I tried the freezer, I tried boiling it then putting in freezer, I tied it to my wheel and ran the engine with the wheel jacked up. Unfortunately it broke loose and flew across the garage and broke the glass, but the red is still at the top.
They will tell you if the car is hot, but not the actual temperature.
I once bought a car that had a moto-meter in place. It curiously always had this full height vertical red stripe appear about 10 minutes after starting. I took it that was the fore-warning that when I shut it off, it was an indicator that it was going to spit and gurgle as that always seemed the association because the event and the notice always went hand in hand.
I kind of liked that feature and it never ever did boil over...but then the honeycomb core on the radiator developed a strange leak...not even much of a pin hole. it always evaporated immediately, but did leave a water stain each time it cooled and I could put 100 miles on it without worrying about a top off.
I could kick myself in the butt because I think I broke the moto-meter when I took the front end apart to add a new Berg's radiator. The red line is just a dot at the bottom and never moves...and I've tried slinging it around in a sock as some say on this forum without success...so for now it is just an ornament...
Maybe when I get around to selling the honeycomb radiator, I can package the broken moto-meter with it for an extra buck or two?
It's a beautiful morning here, I'm going out to play
The impression I've developed after a few years of forumizing and driving is that a motometer is much more functional as a nugatory bit of garnish than it is a gauge, and mine sits atop a cute set of brass wings, so it's extra garnishy. _At car shows, the motometer is another nice antediluvian accouterment to demonstrate for interested spectators, like the two-man top, the one-man oil lamps and a dance I like to call "the three-pedal two-step."
True, my motometer shows more red when the engine is hotter and less when the engine is cooler, but I think it'd be kind of a laugh to expect any kind of accuracy from a gadget that chronically develops bubbles in the viewing glass due to vibration—and Tin Lizzies do vibrate. _It's definitely the seltzer-bottle of sight-gauges.
I'm fortunate in that, so far, whatever the weather, I've yet to see actual steam emanating from anywhere—and with leaky filler neck such as I have, if there were steam, I'd see it. _So overheating doesn't seem to be a significant problem with my old Ford.
Hood ornament or not, I think having a motometer is better than not having a motometer, particularly if you favorite color happens to be red._
They are all different it seems, but you can take the temperature either on or off the car and make a note of what the lines really mean.
I like having it on there because it gives me a little bit of a heads up on what's going on in there. I guess I got lucky and got one that was actually fixable. It's not so much a gauge. I would akin it to our modern day idiot lights. As long as it's not way up there, you're fine. If it turns red, something's wrong.