Chrysler Full-Size Trucks 1967-1988 Repair Guide

Cooling System


See Figure 1

Never remove the radiator cap under any conditions while the engine is running! Failure to follow these instructions could result in damage to the cooling system or engine and/or in personal injury. To avoid having scalding hot coolant or steam blow out of the radiator, DO NOT remove the cap from a hot radiator. Wait until the engine has cooled sufficiently, then wrap a thick cloth around the radiator cap and turn it SLOWLY to the first stop. Step back while the pressure is released from the cooling system. When you are sure the pressure has been released, press down on the radiator cap (still have the cloth in position) turn and remove the radiator cap.

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Fig. Fig. 1: Fill and drain locations of the cooling system


See Figures 2 and 3

At least once every 2 years, the engine cooling system should be inspected, flushed, and refilled with fresh coolant. If the coolant is left in the system too long, it loses its ability to prevent rust and corrosion. If the coolant has been diluted with too much water, it won't protect against freezing.

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Fig. Fig. 2: Be sure the rubber gasket has a tight seal

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Fig. Fig. 3: On radiator caps equipped with a top lever, lift the lever to release pressure

The radiator cap should be examined for signs of age or deterioration. Fan belts should be inspected and, if necessary, adjusted to the proper tension (please refer to Belt Tension Adjustment in this section).

Hose clamps should be tightened, and soft or cracked hoses replaced. Damp spots, or accumulations of rust or dye near hoses, the water pump or other areas, indicate possible leakage. This must be corrected before filling the system with fresh coolant.

Checking The Radiator Cap

While you are checking the coolant level, check the radiator cap for a worn or cracked gasket. If the cap doesn't seal properly, fluid will be lost in the form of steam and the engine will overheat. If necessary, replace the cap with a new one.

Radiator Debris

See Figure 4

Periodically clean any debris (leaves, paper, insects, etc.) from the radiator fins. Pick the large pieces off by hand. The smaller pieces can be washed away with water pressure from a hose.

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Fig. Fig. 4: Remove debris from the radiator fins

Carefully straighten any bent radiator fins with a pair of needle nose pliers. Be careful; the fins are very soft! Don't wiggle the fins back and forth too much. Straighten them once and try not to move them again.


Coolant found in late model trucks is normally a 50/50 mixture of ethylene glycol and water which can be used year round. Always use a good quality antifreeze with water pump lubricants, rust and other corrosion inhibitors, and acid neutralizers. Also available is another type of anitfreeze, Propylene Glycol, which is non-toxic. Keep in mind that should you decide to use a Propylene Glycol antifreeze, you should follow the antifreeze manufacturer's instructions closely. Do not mix Ethyene and Propylene Glycol together, as the benefits of the non-toxic Propylene Glycol would be lost. In the event you decide to change to Propylene Glycol, make sure to completely flush the cooling system of all Ethyene Glycol traces.


See Figures 5 and 6

The system should be completely drained and refilled at least every two years in order to remove accumulated rust, scale and other deposits.

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Fig. Fig. 5: Most late model vehicles are equipped with a coolant recovery system

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Fig. Fig. 6: The cooling system should be checked periodically using a pressure tester


See Figure 7

  1. Remove the radiator cap. Drain the existing coolant by opening the radiator draincock and engine draincock (if equipped, located on the water pump housing) or by disconnecting the bottom radiator hose at the radiator outlet.

Before opening the radiator draincock, spray it with some penetrating lubricant.

  1. Close the draincock or re-connect the lower hose and fill the system with water.
  3. Add a can of quality radiator flush.
  5. Idle the engine until the upper radiator hose gets hot.
  7. Drain the system again.
  9. Repeat this process until the drained water is clear and free of scale.
  11. Close all draincocks and connect all the hoses.
  13. If equipped with a coolant recovery system, flush the reservoir with water and leave empty.
  15. Determine the capacity of your cooling system (see the Capacities Chart). Add a 50/50 mix of quality antifreeze and water to provide the desired protection.

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Fig. Fig. 7: Filling the Cooling System

  1. Run the engine to operating temperature.
  3. Stop the engine and check the coolant level.
  5. Check the level of protection with an antifreeze tester, replace the cap and check for leaks.