Isuzu Cars and Trucks 1981-1991

Cooling System


Once a month, the engine coolant level should be checked. This is quickly accomplished by observing the level of coolant in the recovery tank, which is the translucent tank mounted to the right of the radiator, and connected to the radiator filler neck by a length of hose. As long as coolant is visible in the tank between the "Full Cold" and "Full Hot" marks the coolant level is OK.

If coolant is needed, a 50/50 mix of ethylene glycol based antifreeze and clear water should always be used for additions, both winter and summer. Add coolant to the recovery tank through the capped opening. If adding coolant to the radiator, make sure the engine is cool before removing the radiator cap.

The radiator hoses, clamps, and radiator cap should be checked at the same time as the coolant level. Hoses which are brittle, cracked, or swollen should be replaced. Clamps should be checked for tightness (screwdriver-tight only _ do not allow the clamp to cut into the hose or crush the fitting). The radiator cap gasket should be checked for any obvious tears, cracks or swelling, or any signs of incorrect seating in the radiator neck.

To avoid injury when working with a hot engine, cover the radiator cap with a thick cloth. Wear a heavy glove to protect your hand. Turn the radiator cap slowly to the first stop, and allow all the pressure to vent (indicated when the hissing noise stops). When the pressure has been released, press down and remove the cap the rest of the way.

The cooling system should be drained, flushed and refilled every 2 years or 30,000 miles, according to the manufacturer's recommendations. However, many mechanics prefer to change the coolant every year; it is cheap insurance against corrosion, overheating or freezing.

  1. Remove the radiator cap when the engine is cool. See the preceding "CAUTION" about removing the cap.
  3. With the radiator cap removed, run the engine until heat can be felt in the upper hose, indicating that the thermostat is open. The heater should be turned on to its maximum heat position, so that the core is flushed out.
  5. Shut off the engine and open the drain cock in the bottom of the radiator. Drain the radiator.
  7. Close the drain cock and fill the system with clear water. A cooling system flushing additive can be added, if desire.
  9. Run the engine until it is hot again.
  11. Drain the system, then flush with water until it runs clear.
  13. Clean out the coolant recovery tank: remove the cap leaving the hoses in place. Remove the tank and drain it of any coolant. Clean it out with soap and water, empty it, and install it.
  15. Close the drain cock and fill the radiator with a 50/50 mix of ethylene glycol based antifreeze and water to the base of the radiator filler neck. Fill the coolant recovery tank with the same mixture to the "Full Hot" mark. Install the recovery tank cap.
  17. Run the engine until the upper radiator hose is hot again (radiator cap still off). With the engine idling, add the 50/50 mix of antifreeze and water to the radiator until the level reaches the bottom of the filler neck. Shut off the engine and install the radiator cap, aligning the arrows with the overflow tube. Turn off the heater.