1968 Dart cooling system & gauge Questions

[68Dart270]

Man, I am really glad the OP asked this question, as I was wondering about the factory temp gauge myself in my '68 GTS. My car usually runs inside this red range (from 45 F to 90 F outside temp):
View attachment 1716545248
I assume that range is around 150-160 F to 195 F, and that is with a 180 F thermostat, aftermarket coolant temp sensor (might read different than a factory/NOS one?), and a factory radiator (part number ending in 026) that has been converted to 3 cores.

The only time I have seen my temp gauge get to where the OP's is when my car has been idling for more than 5 minutes (say to adjust timing). Using a thermal imaging camera (nothing too expensive, it plugs in to the bottom of a phone) to check temps under hood when the car is idling after driving (so my temp gauge is at the same spot as the OP's picture), the top of the radiator is around 185-190 F, the thermostat housing is around 200-205 F and the area of the intake that the coolant temp sensor is threaded into is also around 200-205 F.

Also neat to learn about the different style radiator caps, I have never seen one that doesn't allow pressure to build until boil-over.

This is where my gauge is today and its 86 out. Dont know what temp thermostat is in my car. Probably should get a 180 degree one so it starts letting the coolant flow sooner. Wish my car ran as cool as yours does. Mine has ac and the 3 row radiator,but dont know if it needs to be nodded out or not.

 

[nickonfire700]

This is where my gauge is today and its 86 out. Dont know what temp thermostat is in my car. Probably should get a 180 degree one so it starts letting the coolant flow sooner. Wish my car ran as cool as yours does. Mine has ac and the 3 row radiator,but dont know if it needs to be nodded out or not.

View attachment 1716545272

That's the thing, I think both our cars are running at the same temp, but our gauges show something different. That's why I said my car has an aftermarket coolant temp sender, maybe it has different resistance values, and shows lower on the gauge than an OEM/NOS temp sender. I bought an NOS temp sender, and I tried to compare the two senders in boiling water with a multi-meter (to get ohm readings) and a meat thermometer (to chart the rising temp and its corresponding ohm reading), and the two senders seem really close to each other value wise, but maybe not. I have to try running the NOS sender one of these days and see where my gauge ends up.

I bought my car with its factory 2 core radiator that was re-cored, and it did an ok job of keeping the car cool, but it would struggle in very heavy traffic. I feel the 3 core was a wise investment, as after sitting in traffic, the car can cool off within a couple miles. Even sitting in traffic, it doesn't get as hot as it used to with the 2 core.

 

[dr dodge]

That's the thing, I think both our cars are running at the same temp, but our gauges show something different. That's why I said my car has an aftermarket coolant temp sender, maybe it has different resistance values, and shows lower on the gauge than an OEM/NOS temp sender. I bought an NOS temp sender, and I tried to compare the two senders in boiling water with a multi-meter (to get ohm readings) and a meat thermometer (to chart the rising temp and its corresponding ohm reading), and the two senders seem really close to each other value wise, but maybe not. I have to try running the NOS sender one of these days and see where my gauge ends up.

I bought my car with its factory 2 core radiator that was re-cored, and it did an ok job of keeping the car cool, but it would struggle in very heavy traffic. I feel the 3 core was a wise investment, as after sitting in traffic, the car can cool off within a couple miles. Even sitting in traffic, it doesn't get as hot as it used to with the 2 core.

I think my 72 dart does not exhaust the heat when not moving
I can pull over when it starts to cook, open the hood, get almost knocked over from the ball of heat,
and almost immediately the vapor-locky (brother of the jaber-wocky) goes away in under 2 minutes
I plan of somehow venting that, as is seems all my x country problems start with unmoving bumper to bumper
factory 4 blade stone stock /6, 19" no shroud
just like mom made it

 

[68Dart270]

That's the thing, I think both our cars are running at the same temp, but our gauges show something different. That's why I said my car has an aftermarket coolant temp sender, maybe it has different resistance values, and shows lower on the gauge than an OEM/NOS temp sender. I bought an NOS temp sender, and I tried to compare the two senders in boiling water with a multi-meter (to get ohm readings) and a meat thermometer (to chart the rising temp and its corresponding ohm reading), and the two senders seem really close to each other value wise, but maybe not. I have to try running the NOS sender one of these days and see where my gauge ends up.

I bought my car with its factory 2 core radiator that was re-cored, and it did an ok job of keeping the car cool, but it would struggle in very heavy traffic. I feel the 3 core was a wise investment, as after sitting in traffic, the car can cool off within a couple miles. Even sitting in traffic, it doesn't get as hot as it used to with the 2 core.

I agree a 3 row radiator is the way to go. Especially if you live when it gets hot and the car has ac which creates even more cooling demand on the radiator since the condenser is in front of the radiator. I've read other people here state that their gauge runs in the middle usually so maybe that's where it runs on a normal 80 or 90° day. I know my other Mopars seem to run in the middle on warmer days and then on cooler days are usually more towards the left.

 

[nickonfire700]

I agree a 3 row radiator is the way to go. Especially if you live when it gets hot and the car has ac which creates even more cooling demand on the radiator since the condenser is in front of the radiator. I've read other people here state that their gauge runs in the middle usually so maybe that's where it runs on a normal 80 or 90° day. I know my other Mopars seem to run in the middle on warmer days and then on cooler days are usually more towards the left.

I would say thankfully my car doesn't have A/C, but it would be nice on those hot days! I just wish Ma Mopar would say in the owners manual that "this is the normal operating temp range on the gauge", instead of everyone guessing. I know most people would install an aftermarket gauge, but I don't want one in my car. I probably just need to not over think this, as I have had the gauge quite high (waiting in a long line to get into a car show on a 95 F + day), and the car has never lost or spit out coolant, and that was with the factory 2 core radiator.

I think my 72 dart does not exhaust the heat when not moving
I can pull over when it starts to cook, open the hood, get almost knocked over from the ball of heat,
and almost immediately the vapor-locky (brother of the jaber-wocky) goes away in under 2 minutes
I plan of somehow venting that, as is seems all my x country problems start with unmoving bumper to bumper
factory 4 blade stone stock /6, 19" no shroud
just like mom made it

If you can afford to stop, I don't disagree with that, that would definitely cool off the motor quicker.

 

[dr dodge]

I would say thankfully my car doesn't have A/C, but it would be nice on those hot days! I just wish Ma Mopar would say in the owners manual that "this is the normal operating temp range on the gauge", instead of everyone guessing. I know most people would install an aftermarket gauge, but I don't want one in my car. I probably just need to not over think this, as I have had the gauge quite high (waiting in a long line to get into a car show on a 95 F + day), and the car has never lost or spit out coolant, and that was with the factory 2 core radiator.

If you can afford to stop, I don't disagree with that, that would definitely cool off the motor quicker.

I am thinking some sort of a hood vent
it's amazing how fast the problem stops when ya open the hood
GT 40's had that problem, hence the hood

 

[68Dart270]

I would say thankfully my car doesn't have A/C, but it would be nice on those hot days! I just wish Ma Mopar would say in the owners manual that "this is the normal operating temp range on the gauge", instead of everyone guessing. I know most people would install an aftermarket gauge, but I don't want one in my car. I probably just need to not over think this, as I have had the gauge quite high (waiting in a long line to get into a car show on a 95 F + day), and the car has never lost or spit out coolant, and that was with the factory 2 core radiator.

If you can afford to stop, I don't disagree with that, that would definitely cool off the motor quicker.

I agree entirely. I detest aftermarket accesories in classic cars. If I wanted a modern car with modern instrumentation I would buy one. I like these cars to be as they came from the factory. No tiny aftermarket thick grip steering wheels,18" modern "rims",etc.
My ac doesnt work,but is all there. I deliberately looked for a car with factory air.
I am thinking that anywhere in the middle range is probably fine and normal. Thats where my other cars usually wind up when driving city traffic on warm days. Still it does comfort me to see the gauge indicator off to the left.
Nice car by the way. Would love to have a GTS or a GT one day.

 

[68Dart270]

I would say thankfully my car doesn't have A/C, but it would be nice on those hot days! I just wish Ma Mopar would say in the owners manual that "this is the normal operating temp range on the gauge", instead of everyone guessing. I know most people would install an aftermarket gauge, but I don't want one in my car. I probably just need to not over think this, as I have had the gauge quite high (waiting in a long line to get into a car show on a 95 F + day), and the car has never lost or spit out coolant, and that was with the factory 2 core radiator.

If you can afford to stop, I don't disagree with that, that would definitely cool off the motor quicker.

Yeah,stop and go traffic is not fun. Ive seen cars overheat at car shows where the cruise around in a circle and dont get going fast enough to move air through the radiator.

 

[Mattax]

With respect to the air through the radiator, idling and stop and go traffic is the worst. Perhaps only exaserbated by a long interstate or mountain driving before being brought to a standstill. A well fitted fan shroud does wonders. I ran without one for a couple of long periods and watching the gage rise while stuck in those situations is never comfy. Then turning on the heater fan to get some more cooling leaves even the coolest of us in a sweat.

Stopping the engine will cause a rise in the coolant temperature. Opening the hood helps but a portion of the engine heat will first go into the oil and coolant.

In fact the temperature rise after stopping is mentioned in the later Operator or Owners Manuals

1967 Barracuda

1975 Valiant

1977 Aspen

 

[68Dart270]

With respect to the air through the radiator, idling and stop and go traffic is the worst. Perhaps only exaserbated by a long interstate or mountain driving before being brought to a standstill. A well fitted fan shroud does wonders. I ran without one for a couple of long periods and watching the gage rise while stuck in those situations is never comfy. Then turning on the heater fan to get some more cooling leaves even the coolest of us in a sweat.

Stopping the engine will cause a rise in the coolant temperature. Opening the hood helps but a portion of the engine heat will first go into the oil and coolant.

In fact the temperature rise after stopping is mentioned in the later Operator or Owners Manuals

1967 Barracuda
View attachment 1716545341

1975 Valiant
View attachment 1716545342

1977 Aspen
View attachment 1716545343

Thank you for posting this info! So it would appear that the middle of the temp gauge is considered to be its normal operating range then.. this is a great site because of folks like you sharing info.