Taking readings at the inlet, out let, front and rear of the head, using an infrared thermometer, what should the running temperatures be on a properly cooling T, with no water pump on a hot 90 degree day?
Just below boiling, 190 to 200 degrees.
Don't know! Probably between 160 and 180, but haven't read that in any literature. Henry didn't install a temperature gauge or even a motometer. A good reference would be that it doesn't boil or steam while driving. It might steam if idling a long time, especially if you don't have a fan blade. It is normal to hear some gurgling soon after you turn off the ignition on a hot day after a hard run, but that should only last a few seconds.
Most important before you start out, be sure your coolant is at least half way up the top tank. And be sure it really is that high. There is a baffle about the fluid level in some radiators and when the baffle is wet after you pour in a little water, you might think it is full enough but you are only looking at the wet baffle.
If you overfill, it is normal for some coolant to run out the overflow pipe as the engine warms up until it reaches the operating level.
Have fun and don't worry about the exact temperature.
How about temperature difference from top of the radiator to the bottom?
Seems like when I checked Mine it was 20 to 30 deg
difference 180s at top 160s at bottom ? but I have a water pump on the 26 touring.
I measured the difference with an infrared thermometer and found the upper tank of the radiator to be 183.5 F. on a 90 degree day, after running 5 miles and at idle the lower pipe measured 121.5 degrees.
The difference of 62 degrees, of the heated coolant in the upper tank after dropping down the radiator on its way back up into the block. That confirmed to me the thermo syphon cooling system was working well.
Dan, I did the same test today. 90 degrees, sunny and humid. It never got over 200 degrees. Most times it was 180 or less. I had a temperature differential of 60-70 degrees from top hose to bottom hose. It never even got hot setting at idle in the sun. I think I have the problem solved!!
If you cant grab the pipe going back up to the engine, and hold onto it, your radiator is likely not doing its job.