Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Mister Luck

cassis tutissima virtus
Joined
Aug 25, 2020
Posts
1,543
Reaction score
516
Location
WEST COAST
Ram Year
2016/2017
Engine
5.7 V8
Re examination of the engine cooling system of the 5.7 Hemi

I’m in the process of replacing the stock radiator.

I’m examining the coolant flow and thermostat location on top of the water pump.

Radiator thermostats are not the most technologically advanced devices and routinely overlooked in maintenance schedules.

The first point I want this discussion to open with is the location of the thermostat on top of the water pump,
why is this considered a optimum location is it just for convenience because they are both generally changed in the same interval where as I believe changing or at least inspection of the thermostat should happen sooner perhaps a 2 to 1 ratio or better.

The other discussion within this thread and the different ideologies of engineering and physics is whether top down coolant flow is better than bottom up flow I’ll refrain from bringing up the point of Left VS Right flow of radiator cores

Many members and in general most vehicle owners prefer to use a lower temperature rated coolant temperature thermostat for example I believe 180 F (82 C) is the most popular.

(I’m waiting on parts as of this date and have lots of questions going into my parts cannon)




A lot of people have misconceptions about coolant thermostats ,

They stop or restrict coolant flow to ally the engine in reaching optimum operating (closed loop) for stoichiometric efficiency sooner.



They do not however maintain the coolant temperature this is by design the function of the radiator.




It is my personal experience that thermostats fail regularly, even advertised “fail-safe“ Thermostats that are intended when they fail to stay locked in the open position.


Radiator Thermostats are the weak link in the cooling system and are not used in racing applications for this reason.


One type of radiator is uniquely suited to a 4th GEN RAM with a 5.7 Hemi V8 is the use of a Double pass cross flow design because the inlet and outlet coolant ports can be conveniently located on the right side of the engine.
1F6DBC47-300A-46B1-B3D3-943D5748970D.jpeg

Multi-pass radiators have an advantage because of their design to have coolant pass twice across the core before returning to the water pump.



Although not a common off the shelf product they can be made from a single pass radiator by dividing the core with a plate and re-routing the core tubing to make a second or third pass modification.


If a thermostat is required (as in the example of emissions controlled vehicles) it is recommended that the thermostat plate is drilled with 2 to 3 small holes to allow coolant to still flow past the thermostat in the event of partial or total failure.

How much removed is at the discretion of the efficiency and effectiveness of the thermostats intended target temperature.


I found this helpful excerpt From
“The interpretation of OBD2”
Coolant Temp sensor
and its role in engine management
COOLANT TEMP SENSOR
CTS DATA
INTERPRETATION

“Coolant temp sensor (range = -40 to 389 F)

The CTS (coolant temperature sensor) is an NTC (negative temperature coefficient) thermistor that creates varying degrees of voltage drop on a 5-volt reference wire that's supplied by the PCM.

The PCM will interpret the voltage drop on the 5-volt reference wire and convert these voltage changes into temperature readings and display it on the scanner.

When the sensor is unplugged, the open circuit from the PCM will be reading 5 volts on the CTS wire and display -40 degrees on the scanner.

When the CTS connector is jumped short circuit, the PCM will be reading "0" volts on the wire and display a reading of 389 degrees. Normal operating range for the sensor, when hot, should be 185 to 220 degrees. Voltage will be 3 volts cold .5 volts hot.

This sensor has a major influence over fuel mixture when the engine is cold. Its influence diminishes as the engine warms up to operating temperature. The CTS and ACT readings should be compared when dealing with a cold start problem make sure they are within 10 degrees of each other when the engine is cold.

The PCM also uses the CTS input to control the cooling fan operation, on some vehicles.

The PCM will turn on the fan if it senses an open or shorted CTS circuit.
This is a fail-safe mode of operation to protect the motor from damage due to overheating.
CTS is also used by the PCM to determine when to activate the torque convert clutch.”

History of the Radiator Thermostat
(and it’s bypass system)
From the perspective of a Jaguar-Type series 3 owner
COOL CAT CORP
it’s a long read but has insight on parts and manufacturers
what the correct type of thermostat will do and what the future holds for thermostats
 
Last edited:

1999 White C5 Coupe

Senior Member
Joined
Jul 12, 2016
Posts
256
Reaction score
295
Ram Year
2014
Engine
Hemi 5.7
Re examination of the engine cooling system of the 5.7 Hemi

I’m in the process of replacing the stock radiator.

I’m examining the coolant flow and thermostat location on top of the water pump.

Radiator thermostats are not the most technologically advanced devices and routinely overlooked in maintenance schedules.

The first point I want this discussion to open with is the location of the thermostat on top of the water pump,
why is this considered a optimum location is it just for convenience because they are both generally changed in the same interval where as I believe changing or at least inspection of the thermostat should happen sooner perhaps a 2 to 1 ratio or better.

The other discussion within this thread and the different ideologies of engineering and physics is whether top down coolant flow is better than bottom up flow I’ll refrain from bringing up the point of Left VS Right flow of radiator cores

Many members and in general most vehicle owners prefer to use a lower temperature rated coolant temperature thermostat for example I believe 180 F (82 C) is the most popular.

(I’m waiting on parts as of this date and have lots of questions going into my parts cannon)

What is your personal philosophy regarding this subject?



How did you determine that, “...most vehicle owners prefer to use a lower temperature rate coolant temperature thermostat for example I believe 180 F (82 C) is the most popular.”?
 

pacofortacos

Senior Member
Joined
Apr 18, 2017
Posts
3,564
Reaction score
4,341
Ram Year
2016
Engine
5.7
I prefer top thermostat location AS LONG AS it has a bleeder hole in the stat.
I would think top down vs. bottom up cooling is probably a pump efficiency thing as it is easier to use gravity than to fight it.

Not a fan of 180 stat on a system designed for max efficiency at 203-220 degrees. I have tried a 190, but went back to the stock stat. I prefer to try to keep the temp steady at 203-206 degrees.

I am a believer in the stat works or it doesn't and don't touch it if it works fine.
 
OP
OP
Mister Luck

Mister Luck

cassis tutissima virtus
Joined
Aug 25, 2020
Posts
1,543
Reaction score
516
Location
WEST COAST
Ram Year
2016/2017
Engine
5.7 V8
I prefer top thermostat location AS LONG AS it has a bleeder hole in the stat.
I would think top down vs. bottom up cooling is probably a pump efficiency thing as it is easier to use gravity than to fight it.

Not a fan of 180 stat on a system designed for max efficiency at 203-220 degrees. I have tried a 190, but went back to the stock stat. I prefer to try to keep the temp steady at 203-206 degrees.

I am a believer in the stat works or it doesn't and don't touch it if it works fine.
Out of sight out of mind
I think the convince is part of the problem of why the thermostat is neglected it usually entails draining coolant and their location’s accessibility.
I’ve seen 100,000 mile thermostats but they were luckily stuck open or partially open and didn’t compound their inefficiencies.
 
OP
OP
Mister Luck

Mister Luck

cassis tutissima virtus
Joined
Aug 25, 2020
Posts
1,543
Reaction score
516
Location
WEST COAST
Ram Year
2016/2017
Engine
5.7 V8
How did you determine that, “...most vehicle owners prefer to use a lower temperature rate coolant temperature thermostat for example I believe 180 F (82 C) is the most popular.”?
What does your 99 CS Coupe use?

its one of those things in forums where someone trying to imply by lowering operating temperatures (sometime artificially) that more hp can be gained and everyone starts buying into it just because where in actual track use it can be beneficial but daily drivers and fuel economy it is not, but thats not what this thread is about
 
Last edited:

Wild one

Senior Member
Joined
Jan 17, 2016
Posts
13,725
Reaction score
23,401
Ram Year
14 Sport
Engine
5.7
I prefer top thermostat location AS LONG AS it has a bleeder hole in the stat.
I would think top down vs. bottom up cooling is probably a pump efficiency thing as it is easier to use gravity than to fight it.

Not a fan of 180 stat on a system designed for max efficiency at 203-220 degrees. I have tried a 190, but went back to the stock stat. I prefer to try to keep the temp steady at 203-206 degrees.

I am a believer in the stat works or it doesn't and don't touch it if it works fine.
It's opposite of that.Suction side is bottom of engine aka lower rad hose,top side is pressure or pump side.That's why the bottom hose has a spring inside it to keep it from collasping under suction.They're also a reverse flow cooling system,same as pretty well all modern engines
 
OP
OP
Mister Luck

Mister Luck

cassis tutissima virtus
Joined
Aug 25, 2020
Posts
1,543
Reaction score
516
Location
WEST COAST
Ram Year
2016/2017
Engine
5.7 V8
It's opposite of that.Suction side is bottom of engine aka lower rad hose,top side is pressure or pump side.That's why the bottom hose has a spring inside it to keep it from collasping under suction.They're also a reverse flow cooling system,same as pretty well all modern engines
Do you think that theory is because heat travels up ?
 

HEMIMANN

Senior Member
Supporting Member
Military
Joined
Dec 7, 2020
Posts
6,807
Reaction score
17,098
Location
Minneapolis, MN
Ram Year
2017 2500 Laramie Crew Cab
Engine
6.4L HEMI
Yikes - a heat transfer thread. My text book is 3 inches thick.

I never thought about stat locale before. They're always at the top of.the block regardless of engine size. My educated speculation is functionality, not service ease. Engineers rarely designed for service in the past. Thermostat is only to heat up engine faster. Why? In vehicles, passenger comfort and now emissions. If low in cooling system, stat would not open, engine could overheat.

Heat transfer is dependent on thermal conductivity, flow rates, and temperature differences. Mfgs always looking for cheapest combo for adequate cooling. Went from copper rads to alum but had to increase size. Net cost reduction. Generally more cost effective to increase airflow instead of coolant flow. At lower flows, crossflow coolant rads more efficient than down flow rads.
And it goes on & on & on...
 

1999 White C5 Coupe

Senior Member
Joined
Jul 12, 2016
Posts
256
Reaction score
295
Ram Year
2014
Engine
Hemi 5.7
What does your 99 CS Coupe use?

its one of those things in forums where someone trying to imply by lowering operating temperatures (sometime artificially) that more hp can be gained and everyone starts buying into it just because where in actual track use it can be beneficial but daily drivers and fuel economy it is not, but thats not what this thread is about


My Corvette uses a factory 195 degree thermostat. My Ram (hemi engine) also has a factory (OEM) thermostat.

I have never installed an engine coolant thermostat in any engine that is lower than the OEM specification. I also use OEM parts.
 
OP
OP
Mister Luck

Mister Luck

cassis tutissima virtus
Joined
Aug 25, 2020
Posts
1,543
Reaction score
516
Location
WEST COAST
Ram Year
2016/2017
Engine
5.7 V8
Yikes - a heat transfer thread. My text book is 3 inches thick.

I never thought about stat locale before. They're always at the top of.the block regardless of engine size. My educated speculation is functionality, not service ease. Engineers rarely designed for service in the past. Thermostat is only to heat up engine faster. Why? In vehicles, passenger comfort and now emissions. If low in cooling system, stat would not open, engine could overheat.

Heat transfer is dependent on thermal conductivity, flow rates, and temperature differences. Mfgs always looking for cheapest combo for adequate cooling. Went from copper rads to alum but had to increase size. Net cost reduction. Generally more cost effective to increase airflow instead of coolant flow. At lower flows, crossflow coolant rads more efficient than down flow rads.
And it goes on & on & on...

What’s the textbook named ?
flow reduction I’m thinking a restrictor and a thermostat that doesn’t fight between coolant flow and temperature changes
but it seems contradictory if slowing the flow increases absorption between heat of the engine block and the cooling of the aluminum or is it more efficient?
 

DILLIGAF

Senior Member
Military
Joined
May 28, 2016
Posts
4,218
Reaction score
7,551
Location
Canada
Ram Year
2012
Engine
5.7
Not a fan of 180 stat on a system designed for max efficiency at 203-220 degrees.

The only reason its designed for 200ish is for Emissions, has zero to do with efficiency. Same reason the put that POS MDS system in. You got to keep those tree hugging snowflakes happy.
 

HEMIMANN

Senior Member
Supporting Member
Military
Joined
Dec 7, 2020
Posts
6,807
Reaction score
17,098
Location
Minneapolis, MN
Ram Year
2017 2500 Laramie Crew Cab
Engine
6.4L HEMI
What’s the textbook named ?
flow reduction I’m thinking a restrictor and a thermostat that doesn’t fight between coolant flow and temperature changes
but it seems contradictory if slowing the flow increases absorption between heat of the engine block and the cooling of the aluminum or is it more efficient?

Introduction to Heat Transfer? It's downstairs on the book shelf.

Heat transfer is the most nonlinear phenomenon I can think of - more so than plastics. The general rule is Q = mc(p)dT. But the coefficients are different for every combo of material and fluid, AND CHANGE with changing temperature! To solve a problem you have to use finite element numerical methods on computer, and even then your answer might be off by 20%. It's just madness.

So, I'd have to look up the convective heat transfer coefficient between coolant and iron, and coolant and aluminum, then hope to find curves for variable flow rates.

See how complex it gets in a hurry?
 
OP
OP
Mister Luck

Mister Luck

cassis tutissima virtus
Joined
Aug 25, 2020
Posts
1,543
Reaction score
516
Location
WEST COAST
Ram Year
2016/2017
Engine
5.7 V8
The only reason its designed for 200ish is for Emissions, has zero to do with efficiency. Same reason the put that POS MDS system in. You got to keep those tree hugging snowflakes happy.
I kind of like hugging trees..
your right it’s designed into the system the hotter the better but then they always need something for the too hot Nox
but grad student, grandma, and average joe couldn’t figure how to adjust a manual choke so here we are knee deep in wires
 
OP
OP
Mister Luck

Mister Luck

cassis tutissima virtus
Joined
Aug 25, 2020
Posts
1,543
Reaction score
516
Location
WEST COAST
Ram Year
2016/2017
Engine
5.7 V8
Introduction to Heat Transfer? It's downstairs on the book shelf.

Heat transfer is the most nonlinear phenomenon I can think of - more so than plastics. The general rule is Q = mc(p)dT. But the coefficients are different for every combo of material and fluid, AND CHANGE with changing temperature! To solve a problem you have to use finite element numerical methods on computer, and even then your answer might be off by 20%. It's just madness.

So, I'd have to look up the convective heat transfer coefficient between coolant and iron, and coolant and aluminum, then hope to find curves for variable flow rates.

See how complex it gets in a hurry?
got to the weekend then its going to rain and the supply chain logistics?
thanks for the formula maybe I can write an algorithm or measure the volume of coolant against the density of the engine block … that book is not for the coffee table
 
OP
OP
Mister Luck

Mister Luck

cassis tutissima virtus
Joined
Aug 25, 2020
Posts
1,543
Reaction score
516
Location
WEST COAST
Ram Year
2016/2017
Engine
5.7 V8
Has anyone have experience using a coolant bypass for the radiator thermostat?
or three 3/16″ or 1/8” holes drilled into the thermostat plate?

What are your ideas regarding coolant flow (pressure) having the reverse effect on a thermostat when it is opening or the stress of the flow when the coolant temperature fluctuates because of increased RPM’s and/or decreased air flow across the radiator?
 
Last edited:

crash68

ACME product engineer
Staff member
Administrator
Supporting Member
Joined
Mar 20, 2016
Posts
10,703
Reaction score
16,709
Ram Year
2015
Engine
3.0 EcoDiesel
Something else to think about before diving into throwing out the thermostat for a restriction plate and oversizing the radiator, the ECM monitors engine temperatures and can set CEL like P0128 which is the engine not warming up faster enough.
Too much or too little flow along with too much of a temperature difference could cause less the optimal conditions for heat transfer.
 
OP
OP
Mister Luck

Mister Luck

cassis tutissima virtus
Joined
Aug 25, 2020
Posts
1,543
Reaction score
516
Location
WEST COAST
Ram Year
2016/2017
Engine
5.7 V8
Something else to think about before diving into throwing out the thermostat for a restriction plate and oversizing the radiator, the ECM monitors engine temperatures and can set CEL like P0128 which is the engine not warming up faster enough.
Too much or too little flow along with too much of a temperature difference could cause less the optimal conditions for heat transfer.
The option of loosing the thermostat altogether isn’t practical at my latitude, my goal is to optimize the system away from stress.

The OE plastic tanked radiator is disposable by design and a aftermarket although if advertised as having more rows actually are close to the same volume because the dimensions do not change only the number of (smaller) rows.

Slowing down coolant flow through the radiator and moving the thermostat to a more accessible location and by this adding longevity to components is all I’m hoping to achieve.

How I do this is still just in the process stages.

Coolant temperature readings are ultimately governed by the ECT sensor and times the closed loop operation.
I want to have a system that follows
protocols more effectively.
 
Last edited:

Wild one

Senior Member
Joined
Jan 17, 2016
Posts
13,725
Reaction score
23,401
Ram Year
14 Sport
Engine
5.7
The option of loosing the thermostat altogether isn’t practical at my latitude, my goal is to optimize the system away from stress.

The OE plastic tanked radiator is disposable by design and a aftermarket although if advertised as having more rows actually are close to the same volume because the dimensions do not change only the number of (smaller) rows.

Slowing down coolant flow through the radiator and moving the thermostat to a more accessible location and by this adding longevity to components is all I’m hoping to achieve.

How I do this is still just in the process stages.

Coolant temperature readings are ultimately governed by the ECT sensor and times the closed loop operation.
I want to have a system that follows
protocols more effectively.
The trucks are designed with enough cooling capacity to run at normal operating temps in places like Dubai,so i don't think you need to try re-engineering the cooling system.Slap a new rad and thermostat in it,check the weep hole on the water pump for a leak,replace it if it's leaking,and call it good.
 

Latest posts

Forum statistics

Threads
194,926
Posts
2,864,180
Members
155,296
Latest member
VLG6963
Top