Stock temp gauge reading versus actual temp - 1963

[UGW]

I recently had the front of the engine apart on my 1963 Imperial. As a "while I'm in here" I replaced the temperature sender (SMS TS-52, RockAuto), because it seemed like it might be reading low.

Now, the readings are different, and I'm trying to figure out if there is just variance in the sensor, of if I am having a cooling problem. The car never overheated before, but I did have the water pump housing off, cooling hoses disconnected, and flushed the cooling system, so it's possible something changed. I welcome others' experiences and input.

Observations:
Previously, in normal driving, it would read about like this:
o----\===|=====----o
On the very hottest days, in heavy traffic, it would read like this:
o----===|=/====----o

Now, after putting everything back together, new sensor, coolant flush, in normal driving, it reads like this:
o----===|=/====----o
And I've seen in go all the way to here, while stopped and idling after driving in traffic:
o----===|=====/----o
THIS FREAKS ME OUT! Granted, I'm used to modern cars with a digital temp gauge that never moves past center unless something is very wrong.

I have an infra-red thermometer, and when I had this reading:
o----===|=/====----o
The reading on the upper radiator hose (which is supposed to be most reliable) was about 170 - 180F

When the reading was here:
o----===|=====/----o
The infra had a reading around 210 - 215F on the hose

More Info:
I live in the city of Chicago, and most of my driving is under 30mph in traffic. It was also above 80F yesterday. Those are harsh conditions for a stock 413 and a stock radiator, but no worse than last summer.
I installed a universal expansion tank last year, which also allows me to fill the radiator all the way to the top. (1963 just had a hose coming off the rad that would puke on the ground) When the engine is cold, fluid sits at the "cold" line. When I see a reading around 210F, the fluid in the tank reaches the "hot" line, but doesn't boil over. When the reading is 170F, the fluid sits between "hot" and "cold".
My car did not originally have AC, so there is no shroud, but it does have a 7-blade, direct-driven Mopar fan - no clutch. I have a universal shroud from Summit I'm in the process of installing, given my driving habits, but it's not installed yet.

 

[CBODY67]

One thing to consider is that with a 15psi pressure radiator cap, the coolant will not "boil" until at least 250*F, so 210*F is not that bad, BUT is over 180*F, which is what many look at as "normal" with a 180*F thermostat. BTAIM

For what you did, I suspect it could well be the variance in sensors. NOT what I'd like to see, but you can always put the old sensor back in and THEN know what the actual temperatures are. NOT to discount the actual temps, though.

You can ALSO use the iR heat gun to check temps at other engine areas. Like the sides of the block, front to back. The parts of the radiator core, top to bottom, inlet to outlet. The thermostat housing itself, too. MANY data points to check!

I haven't seen the universal fan shroud, but hope it is more of a smooth, curved venturi style rather than flat sheet metal as the electric fan shrouds seem to be these days. Where it seems that all of the air is being drawn-through the radiator area where the fan actually is.

Presuming you refilled the cooling system with coolant/water, coolant "concentrate" and water rather than a 50-50 pre-mix?

Take care,
CBODY67

 

[UGW]

Thanks so much!

One thing to consider is that with a 15psi pressure radiator cap, the coolant will not "boil" until at least 250*F, so 210*F is not that bad, BUT is over 180*F, which is what many look at as "normal" with a 180*F thermostat. BTAIM
It's my understanding that a 180F thermostat doesn't mean the engine will never get hotter than 180, just that's when it is fully open? Whatever pressure is in the system, it's enough to move coolant to and from the overflow tank. Not sure if that means anything?

For what you did, I suspect it could well be the variance in sensors. NOT what I'd like to see, but you can always put the old sensor back in and THEN know what the actual temperatures are. NOT to discount the actual temps, though.
Sadly, I don't have the old sensor anymore, and changing it is a PITA because it's underneath the AC compressor. I have to disconnect the whole compressor from the block to reach it. I may get another sensor from a different brand, but that's a last resort.

You can ALSO use the iR heat gun to check temps at other engine areas. Like the sides of the block, front to back. The parts of the radiator core, top to bottom, inlet to outlet. The thermostat housing itself, too. MANY data points to check!
I have done this. The problem is emmicity (sp?) - different materials and colors can read very differently. Brass radiator painted gloss black, flat black rubber hose, shiny blue engine block all need a different setting, and I haven't found settings for all of those. Black rubber seems to be around .90 - .95 on a lot of sources, though, and the hose has fluid flowing through it, so most sources say it's a good point.

I haven't seen the universal fan shroud, but hope it is more of a smooth, curved venturi style rather than flat sheet metal as the electric fan shrouds seem to be these days. Where it seems that all of the air is being drawn-through the radiator area where the fan actually is.
It is more of the flat style, with angled sides, but given its an 18" fan on a 22" x 18" radiator, the fan still covers most of it.

Presuming you refilled the cooling system with coolant/water, coolant "concentrate" and water rather than a 50-50 pre-mix?
Yes - why? I never buy the 50-50 because it seems dumb to pay for water, but didn't know it was inferior.

 

[72DL41]

I think the fan shroud would help. My '72 Polara (360, no A/C, 22" radiator, no shroud) would run "hot" in traffic (Woodward Dream Cruise, etc.). I couldn't find a shroud even though the factory parts catalog specified a part number. I found out the reason it didn't come with one was because it didn't have the "Clean Air Package." I bought a '70-'73 B/E body shroud and made four mounting brackets. It looks factory and runs cooler.

 

[CBODY67]

The only real issue I have seen with IR heat guns, at least the ones I have had, is that they do not like to read ice.

No matter the color, I consider the heat read to be reasonably accurate. Rather than look at "numbers", I look for trends in results. For example, a crossflow radiator that reads cold at the bottom and toward the middle is clogged. An engine block that is a good bit hotter near cyls 5 and 7 needs the core plugs knocked out and the accumulations in them cleaned.

Seems like there are other locations where the heat sensor can screw into the water pump housing? The "hot/cold" light switch is on the passenger side of the housing on our '66 383, for example.

Hope you get everything worked out,
CBODY67

 

[Rubatoguy]

I recently had the front of the engine apart on my 1963 Imperial. As a "while I'm in here" I replaced the temperature sender (SMS TS-52, RockAuto), because it seemed like it might be reading low.

Now, the readings are different, and I'm trying to figure out if there is just variance in the sensor, of if I am having a cooling problem. The car never overheated before, but I did have the water pump housing off, cooling hoses disconnected, and flushed the cooling system, so it's possible something changed. I welcome others' experiences and input.

Observations:
Previously, in normal driving, it would read about like this:
o----\===|=====----o
On the very hottest days, in heavy traffic, it would read like this:
o----===|=/====----o

Now, after putting everything back together, new sensor, coolant flush, in normal driving, it reads like this:
o----===|=/====----o
And I've seen in go all the way to here, while stopped and idling after driving in traffic:
o----===|=====/----o
THIS FREAKS ME OUT! Granted, I'm used to modern cars with a digital temp gauge that never moves past center unless something is very wrong.

I have an infra-red thermometer, and when I had this reading:
o----===|=/====----o
The reading on the upper radiator hose (which is supposed to be most reliable) was about 170 - 180F

When the reading was here:
o----===|=====/----o
The infra had a reading around 210 - 215F on the hose

More Info:
I live in the city of Chicago, and most of my driving is under 30mph in traffic. It was also above 80F yesterday. Those are harsh conditions for a stock 413 and a stock radiator, but no worse than last summer.
I installed a universal expansion tank last year, which also allows me to fill the radiator all the way to the top. (1963 just had a hose coming off the rad that would puke on the ground) When the engine is cold, fluid sits at the "cold" line. When I see a reading around 210F, the fluid in the tank reaches the "hot" line, but doesn't boil over. When the reading is 170F, the fluid sits between "hot" and "cold".
My car did not originally have AC, so there is no shroud, but it does have a 7-blade, direct-driven Mopar fan - no clutch. I have a universal shroud from Summit I'm in the process of installing, given my driving habits, but it's not installed yet.

I would suggest the simplest way to go would be to unplug the temp sensor, and put it in a container with water at a known temp - say use a kitchen thermometer to measure the water temp - then compare it with the gauge. Check youtube as there are a number of videos in how to calibrate a manual temperature gauge. You also find a shop manual or ask around as often the manual will state which needle position corresponds to what temperature. Some gauges even have dots or a marking for specific temperatures that are not part of the visible gauge face. (Not helpful if you don't want to remove the gauge.)

Todd

 

[UGW]

@CBODY67 believe me, I wish I could find another, more convenient, location for a sender. I'd just abandon the current one and relocate the wire, permanently. Unfortunately, it seems like the 62-63 housing only has that one port on the driver's side. (Side note, I now understand why my father, a former mechanic, used to special order his cars with AC delete - it's always in the way!) Thanks for all the other diagnostic tips, I'll check those out.

@Rubatoguy yeah, I don't want to remove the sender if I can just figure out the accuracy. You did give me a good idea, though! I've got a grill thermometer with a hand-held display and a wireless probe. If I can find a safe place to wedge the probe, I could compare that reading. I could even monitor in real time while driving.

The shop manual contains this picture, but I think it may just be generic, because the actual gauge doesn't look anything like that. The 1963 owner's manual isn't much help, either. It just says "shut the car off if the needle goes all the way to H", otherwise any reading is acceptable. (It's almost like they knew the gauge was nearly useless!)

 

[CBODY67]

Using your wireless probe, provided the metal in the car body would not deflect the signal, you might wire-tie it to the upper radiator hose and put some heat-shielding insulation around it?