Cherokee 4WD L6-4.0L VIN S (1998)
Coolant: Description and Operation
Coolant Performance
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.
100 Percent Ethylene-Glycol-Should Not Be Used in Chrysler Vehicles
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 49° 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 Formulations-Should Not Be Used in Chrysler Vehicles
Propylene-glycol formulations do not meet Chrysler coolant specifications. 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 in Chrysler vehicles, which are 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-Should Not Be Used in Chrysler Vehicles
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.
CAUTION: Richer antifreeze mixtures cannot be measured with normal field equipment and can cause problems associated with 100 percent
ethylene-glycol.
