The red fluid in my moto meter has separated now where is the correct reading for the water temp. Is it at the top of the separated part or the level of the part that comes up from the bottom of the Gauge? Is there any way to fix this?
Never lay it down - that's one of the reasons the fluid separates. You can try pounding it firmly down on an inflated tire - with the right technique and some patience it should work. Other methods includes centrifugal force - you can fab a fixture that holds the moto meter secure while it spins fast, like in a lathe. Some fearless restorers tie them to a rope and swings them around, but please be careful out there..
John...mine did that and I gently put it in a vice and also gently heated it up to the very top with a propane torch. It fixed it, but will admit that it didn't last forever. So last week I did it again. Figure doing that two or three times a year is cheaper than a new moto meter.
I had success pounding the bottom on a tire.
John, in answer to the first part of your question, since the volume of the fluid in the tube has not changed, and the dye is there just to allow you to better see the level. the correct reading would still be at the very top of the liquid where the original reading would have been had it not separated. Jim Patrick
I have used the "tie it to a rope & swing method " with great success. I use 1/8" nylon line. Be very careful you have room to swing. About 15 ft radius.
I am not sure what your question means about the correct reading. I do know that at room temperature my gauge has no red liquid visible - its all below the gauge.
In time, a chemistry major will perhaps add his/her insight to this....in the meantime, consider how the gauge operates...by heat, no?
The liquid in the tube warms (gets hot) due to the water vapor (steam) in the radiator neck. As the red liquid gets hot, it expands, rising in the tube.
I do believe that air is more responsive to heat than liquid - at least its molecules become more agitated and thus expand greater...larger volume. That being hypothesized, IF it is true, then ANY amount of air in the tube, separating the red liquid, would render any reading incorrect. NO? I do believe the readings you see with any separation of liquid are meaningless.
So much for my theory...corrections?
Your theory is correct.
Here are the facts from the maker's hand.
And factory way to 'fix' a Motometer.
The safest way is to put it in a very cold freezer. Get all the liquid back down in the bulb if possible.