It’s normal for the coolant temperature when taken at the back of the engine to be 10°-15°F lower than what is happening at the thermostat.  That’s simply due to temperature at the back of the head not yet taking into account the rise in temperature that will occur as the coolant flows back to the front of the engine towards the thermostat.

It takes trips of at least fifteen miles to keep condensation formation minimal and that’s with a properly designed PCV valve system in place.  A good PCV valve system does help to alleviate some of that condensation build up much quicker than the original road draft tube system.  Running a engine oil with too heavy a viscosity will also promote condensation buildup.

Lorena, Texas (South of Waco)

Hi Ted,

It's up in the back top of the head.

The oil on the underside of the valve covers and up at the top inside the filler neck shows condensation.

Even running long trips it does not seem to get very hot.


1959 Edsel Ranger, 1916 Ford "speedster"
"I may not be a rich man, but I can give you a million dollars' worth of bad publicity."

Where is the coolant temperature sensor located?  The original sensor location at the rear of the engine is biased towards reading a lower than actual temperature.  The ideal location is at the front of the engine just behind the thermostat.  Avoid using the outlet holes in the water pump for temperature sensor locations.

Lorena, Texas (South of Waco)

It's distilled water

1959 Edsel Ranger, 1916 Ford "speedster"
"I may not be a rich man, but I can give you a million dollars' worth of bad publicity."

Your water might have too much lead in it.

"FREE SAMPLE"

All the brands I have tried so far wiggle side to side while sitting in the seat.

1959 Edsel Ranger, 1916 Ford "speedster"
"I may not be a rich man, but I can give you a million dollars' worth of bad publicity."

This is in the heat of summer.

I know not all thermostats are created alike.    For instance.  My 68 DeVille had many different brands listed, however ONLY the one with a brass foot that reached down into the by-pass was the correct one.  

I will try the hot water test.  However I've had 3 now.  The odds all are bad???


1959 Edsel Ranger, 1916 Ford "speedster"
"I may not be a rich man, but I can give you a million dollars' worth of bad publicity."

I've had this issue of not getting to running temp, especially in colder weather. The first car I sold before ever working out what the issue was. 
My Landcruiser was doing the same thing, running cold in the cold weather. There is a rubber seal on the thermostat that seals it to the housing. With out being obvious the seal had compressed a little and water was getting past before the thermostat was opening. 
If you have tested your thermostat to see that it is opening and closing properly,(I do that even with new ones as I have heard of them being faulty from new) then I would suggest putting some compatible sealer on the outer edge of the thermostat to make sure no water is getting past it. 

I’m inclined to agree with Charles and RB. Somehow, water is circulating thru the radiator when it shouldn’t. Most of the temperature post are overheating. Since you’ve got an infrared thermometer, have you tried checking the usual places from cold as the engine warms up? You should see a spike in the temp at the upper radiator hose when the stat opens. At your temperatures, you should be able to do it with your hand. The engine temp, bypass hose temp, water pump temp, should all come up before the upper radiator hose. If it doesn’t, it’s bypassing somehow. When you turn the heater on (water control, not fan) you should see that too.

55 years ago my Dad taught me to never put a thermostat in the car, new or used, without putting it in a pot of water on the stove. Suspended on a wire in the water, not touching the pot. (I got in a lot more trouble than he did for using Mom’s candy thermometer).

You can see the stat open, shut off the heat and watch it close. Pretty good proof.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Sounds like flow is somehow by-passing the thermostat..  MELs used a couple different dia of thermostat..  Does yours fit snug in the water neck?  Are you getting flow through your heater core?