Dodge Nitro. Manual - part 515

ETHYLENE-GLYCOL MIXTURES 

The required ethylene-glycol (antifreeze) and water mixture depends upon the climate and vehicle operating 
conditions. The recommended mixture of 50/50 ethylene-glycol and water will provide protection against 
freezing to -37°C (-35°F). The antifreeze concentration must always be a minimum of 44 percent, year-round 
in all climates. If percentage is lower than 44 percent, engine parts may be eroded by cavitation, and 
cooling system components may be severely damaged by corrosion. Maximum protection against freezing is 
provided with a 68 percent antifreeze concentration, which prevents freezing down to -67.7°C (-90°F). A higher 
percentage will freeze at a warmer temperature. Also, a higher percentage of antifreeze can cause the engine to 
overheat because the specific heat of antifreeze is lower than that of water. 

Use of 100 percent ethylene-glycol will cause formation of additive deposits in the system, as the corrosion 
inhibitive additives in ethylene-glycol require the presence of water to dissolve. The deposits act as insulation, 
causing temperatures to rise to as high as 149°C (300°F). This temperature is hot enough to melt plastic and 
soften solder. The increased temperature can result in engine detonation. In addition, 100 percent ethylene-
glycol freezes at 22°C (-8°F). 

PROPYLENE-GLYCOL MIXTURES 

It's overall effective temperature range is smaller than that of ethylene-glycol. The freeze point of 50/50 
propylene-glycol and water is -32°C (-26°F). 5°C higher than ethylene-glycol's freeze point. The boiling point 
(protection against summer boil-over) of propylene-glycol is 125°C (257°F) at 96.5 kPa (14 psi), compared to 
128°C (263°F) for ethylene-glycol. Use of propylene-glycol can result in boil-over or freeze-up on a cooling 
system designed for ethylene-glycol. Propylene glycol also has poorer heat transfer characteristics than ethylene 
glycol. This can increase cylinder head temperatures under certain conditions. 

Propylene-glycol/ethylene-glycol mixtures can cause the destabilization of various corrosion inhibitors, causing 
damage to the various cooling system components. Also, once ethylene-glycol and propylene-glycol based 
coolants are mixed in the vehicle, conventional methods of determining freeze point will not be accurate. Both 
the refractive index and specific gravity differ between ethylene glycol and propylene glycol. 

DESCRIPTION 

GAS ENGINES 

CAUTION: Richer antifreeze mixtures cannot be measured with normal field 

equipment and can cause problems associated with 100 percent ethylene-
glycol.

WARNING:

Antifreeze is an ethylene glycol based coolant and is harmful if swallowed 
or inhaled. If swallowed, drink two glasses of water and induce vomiting. 
If inhaled, move to fresh air area. Seek medical attention immediately. Do 
not store in open or unmarked containers. Wash skin and clothing 
thoroughly after coming in contact with ethylene glycol. Keep out of reach 
of children. Dispose of glycol based coolant properly, contact your 
government agency for location of collection center in your area. Do not 
open a cooling system when the engine is at operating temperature or hot 

 

2007 Dodge Nitro R/T 

2007 ENGINE Cooling - Nitro

  

The cooling system is designed around the coolant. The coolant must accept heat from engine metal, in the 
cylinder head area near the exhaust valves and engine block. Then coolant carries the heat to the radiator where 
the tube/fin radiator can transfer the heat to the air. 

The use of aluminum cylinder blocks, cylinder heads, and water pumps requires special corrosion protection. 
Mopar® Antifreeze/Coolant, 5 Year/100,000 Mile Formula (MS-9769), or the equivalent ethylene glycol based 
coolant with hybrid organic corrosion inhibitors (called HOAT, for Hybrid Organic Additive Technology) is 
recommended. This coolant offers the best engine cooling without corrosion when mixed with 50% Ethylene 
Glycol and 50% distilled water to obtain a freeze point of -37°C (-35°F). If it loses color or becomes 
contaminated, drain, flush, and replace with fresh properly mixed coolant solution. 

The green coolant MUST NOT BE MIXED with the orange or magenta coolants. When replacing coolant the 
complete system flush must be performed before using the replacement coolant. 

DIESEL ENGINE 

The cooling system is designed around the coolant. The coolant must accept heat from engine metal, in the 
cylinder head area near the exhaust valves and engine block. Then coolant carries the heat to the radiator where 
the tube/fin radiator can transfer the heat to the air. 

The use of aluminum cylinder blocks, cylinder heads, and water pumps requires special corrosion protection. 
Glysantin G 30-91 Antifreeze/Coolant, 5 Year/150,000 Mile Formula (ASTM D3306), or the equivalent 
ethylene glycol based coolant. This coolant offers the best engine cooling without corrosion when mixed with 
50% coolant and 50% distilled water to obtain a freeze point of -36°C (-34°F). It is dyed purple to distinguish 
it's unique chemistry from traditional green and yellow silicate coolants. If it loses color or becomes 
contaminated, drain, flush, and replace with fresh properly mixed coolant solution. 

The purple coolant MUST NOT BE MIXED with the orange, green or magenta coolants. When replacing 

under pressure, personal injury can result. Avoid radiator cooling fan 
when engine compartment related service is performed, personal injury 
can result.

CAUTION: Use of Propylene Glycol based coolants is not recommended, as they 

provide less freeze protection and less boiling protection.

CAUTION: Mopar® Antifreeze/Coolant, 5 Year/100,000 Mile Formula (MS-9769) may 

not be mixed with any other type of antifreeze. Doing so will reduce the 
corrosion protection and may result in premature water pump seal failure. 
If non-HOAT coolant is introduced into the cooling system in an 
emergency, it should be replaced with the specified coolant as soon as 
possible.

CAUTION: Use of Propylene Glycol based coolants is not recommended, as they 

provide less freeze protection and less boiling protection.

 

2007 Dodge Nitro R/T 

2007 ENGINE Cooling - Nitro

  

coolant the complete system flush must be performed before using the replacement coolant. 

OPERATION 

OPERATION 

Coolant flows through the engine block absorbing the heat from the engine, then flows to the radiator where the 
cooling fins in the radiator transfers the heat from the coolant to the atmosphere. During cold weather the 
ethylene-glycol or coolant prevents water present in the cooling system from freezing within temperatures 
indicated by mixture ratio of coolant to water. 

DIAGNOSIS AND TESTING 

COOLANT-CONCERTRATION TESTING 

Coolant concentration should be checked when any additional coolant was added to system or after a coolant 
drain, flush and refill. The coolant mixture offers optimum engine cooling and protection against corrosion 
when mixed to a freeze point of -37°C (-34°F) to -46°C (-50°F). The use of a hydrometer or Tool 8266, 
refractometer can be used to test coolant concentration. 

A hydrometer will test the amount of glycol in a mixture by measuring the specific gravity of the mixture. The 
higher the concentration of ethylene glycol, the larger the number of balls that will float, and higher the freeze 
protection (up to a maximum of 60% by volume glycol). 

A Refractometer Tool 8286 will test the amount of glycol in a coolant mixture by measuring the amount a beam 
of light bends as it passes through the fluid. 

Some coolant manufactures use other types of glycols into their coolant formulations. Propylene glycol is the 
most common new coolant. However, propylene glycol based coolants do not provide the same freezing 
protection and corrosion protection and are not recommended. 

CONTAINER-COOLANT RECOVERY 

DESCRIPTION 

DESCRIPTION-PRESSURE SYSTEM 

This system works on the principal of a closed and deaerated system using thermally generated pressure. The 
expansion and contraction of the coolant in the pressurized closed system keeps it free of trapped air. It 

CAUTION: Glysantin G 30-91 Antifreeze/Coolant, 5 Year/150,00 Mile Formula (ASTM 

D3306) may not be mixed with any other type of antifreeze. Doing so will 
reduce the corrosion protection and may result in premature water pump 
seal failure.

CAUTION: Do not mix types of coolant - corrosion protection will be severely 

reduced.

 

2007 Dodge Nitro R/T 

2007 ENGINE Cooling - Nitro

  

provides: 

A pressurized surge tank volume for expansion and contraction.  

A non-pressurized overflow volume to capture excess coolant expansion and allow for it's return to the 
pressurized system.  

A pressurized cap on the pressure bottle rather than the radiator. This facilitates deaeration of the system. 

Reserve coolant is included in the pressurized volume to account for minor leaks and evaporation or 
boiling losses.  

Provides a warning light for low coolant level.  

DESCRIPTION-NON-PRESSURE SYSTEM 

This system works on the principal of a closed and completely deaerated system using thermally generated 
pressure. The bottle acts as a reserve coolant source to keep air out of the system but must have a specified 
minimum amount of coolant in the bottle at all times. The expansion and contraction of the coolant in the 
pressurized closed coolant loop allows the reserve bottle to accept and give up excess fluid via a hose from the 
radiator neck. It provides: 

A non-pressurized reserve coolant tank volume for expansion and contraction of coolant.  

A pressurized cap on the radiator. This keeps the main loop of the cooling system at an elevated operating 
pressure and prevents coolant boiling at lower temperatures.  

Reserve coolant is included in the non-pressurized tank in enough quantity to account for minor leaks and 
evaporation or boiling losses, and to keep the return line back to the radiator full at all times. Failure to do 
so could allow air to be sucked back into the radiator as the engine and engine coolant cool down and the 
coolant volume contracts.  

OPERATION 

OPERATION-PRESSURE SYSTEM 

As the engine warms, the coolant in the closed system expands. The pressurized bottle accepts the expanding 
fluid. Then, when the thermostat opens and a high demand for coolant is placed on the system, the pressurized 
surge tank side of the bottle can supply the temporary additional volume of coolant demanded by the system. 
Once the water pump catches up with the flow demand, the tank returns to equilibrium. A separate compartment 
in the bottle accepts the overflow coolant which is then drawn back into the primary side of the bottle when the 
engine and coolant cool down 

The advantage of the pressurized system is that any excess air in the cooling system is routed to the top of the 
bottle via a vent hose at the thermostat housing to the bottle. This air accumulates at the top of the pressurized 
volume in the bottle (the highest point in the system) and is forced out of the system through the pressure cap. 
This keeps the system properly deaerated and maintains pressure in the cooling system to prevent water pump 
cavitation 

The diesel bottle has an additional vent line back to the radiator that is immersed in the coolant bath at the 
bottle. This also ensures air at the radiator is routed back to bottle for expulsion and that a constant head of 
liquid is present at the radiator. 

 

2007 Dodge Nitro R/T 

2007 ENGINE Cooling - Nitro