Mister Luck
cassis tutissima virtus
- Joined
- Aug 25, 2020
- Posts
- 1,651
- Reaction score
- 588
- 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.
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
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.
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
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