Grand Cherokee 2WD V6-3.7L (2008)
Coolant: Description and Operation
Coolant - Description
Description
DESCRIPTION
WARNING: Antifreeze is an ethylene glycol base 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 base coolant
properly, contact your dealer or 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 under pressure, personal injury can result. Avoid radiator cooling fan when engine compartment
related service is performed, personal injury can result.
ETHYLENE-GLYCOL MIXTURES
CAUTION: Richer antifreeze mixtures cannot be measured with normal field equipment and can cause problems associated with 100 percent
ethylene-glycol.
The use of aluminum cylinder blocks, cylinder heads and water pumps requires special corrosion protection. Only Mopar(R) Antifreeze/Coolant, 5
year/100,000 Mile Formula (ethylene-glycol base coolant with corrosion inhibitors called HOAT, for Hybrid Additive Technology) is recommended.
This coolant offers the best engine cooling without corrosion when mixed with 50% distilled water to obtain a freeze point of -37°C (-35°F).
The required ethylene-glycol (antifreeze) and water mixture depends upon the climate and vehicle operating conditions. 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%
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.
HOAT Coolant
HOAT COOLANT
WARNING: Antifreeze is an ethylene-glycol base 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 base coolant
properly, contact your dealer or 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 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 corrosion protection.
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(R) Antifreeze/Coolant, 5
Year/100,000 Mile Formula (MS-9769), or the equivalent ethylene-glycol base coolant with organic corrosion inhibitors (called HOAT, for Hybrid
