GM Blazer/Jimmy/Typhoon/Bravada 1983-1993 Repair Guide

Cooling System

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See Figures 1 and 2


CAUTION
Never remove the radiator cap under any conditions while the engine is hot! Failure to follow these instructions could result in damage to the cooling system, engine and/or personal injury. To avoid having scalding hot coolant or steam blow out of the radiator, use extreme care whenever you are removing the radiator cap. Wait until the engine has cooled, 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 cap.

Dealing with the cooling system can be a dangerous matter unless the proper precautions are observed. It is best to check the coolant level in the radiator when the engine is cold. All vehicles covered by this information should be equipped with a coolant recovery tank. If the coolant level is at or near the ADD/FULL COLD line (engine cold) or the FULL HOT line (engine hot), the level is satisfactory. Always be certain that the filler caps on both the radiator and the recovery tank are closed tightly.



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Fig. Fig. 1: Coolant protection can be easily checked using a float-type hydrometer tester



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Fig. Fig. 2: If possible, a hand-held pressure tester should be used at least once a year to check system integrity

In the event that the coolant level must be checked when the engine is hot and the vehicle is not equipped with a coolant recovery tank, place a thick rag over the radiator cap and slowly turn the cap counterclockwise until it reaches the first detent. Allow all hot steam to escape. This will allow the pressure in the system to drop gradually, preventing an explosion of hot coolant. When the hissing noise stops, carefully remove the cap the rest of the way.

If the coolant level is found to be low, add a 50/50 mixture of ethylene glycol-based antifreeze and clean water. If not equipped with a recovery tank, coolant must be added through the radiator filler neck. On most models, which are equipped with a recovery tank, coolant may be added either through the filler neck on the radiator or directly into the recovery tank.


CAUTION
Never add coolant to a hot engine unless it is running. If it is not running you run the risk of cracking the engine block.

It is wise to pressure check the cooling system at least once per year. If the coolant level is chronically low or rusty, the system should be thoroughly checked for leaks.

At least once every 2 years or 30,000 miles, 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 too much water, it won't protect against freezing.

The pressure cap should be examined for signs of age or deterioration. Fan belt and other drive belts should be inspected and adjusted to the proper tension. (See checking belt tension).

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

FLUID RECOMMENDATIONS



Whenever adding or changing fluid, use a good quality ethylene glycol antifreeze (one that will not effect aluminum), mix it with water until a 50-50 antifreeze solution is attained.

LEVEL CHECK



See Figures 3 and 4

On most late model vehicles, the fluid level may be checked by observing the fluid level marks of the recovery tank (see through plastic bottle). The level should be near the ADD or FULL COLD mark, as applicable, when the system is cold. At normal operating temperatures, the level should be above the ADD/FULL COLD mark or, if applicable, between the ADD/FULL COLD and the FULL HOT marks. Only add coolant to the recovery tank as necessary to bring the system up to a proper level.


CAUTION
Should it be necessary to remove the radiator cap, make sure that the system has had time to cool, reducing the internal pressure.

On any vehicle that is not equipped with a coolant recovery or overflow tank, the level must be checked by removing the radiator cap. This should only be done when the cooling system has had time to sufficiently cool after the engine has been run. The coolant level should be within 2 in. (51 mm) of the base of the radiator filler neck. If necessary, coolant can then be added directly to the radiator.



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Fig. Fig. 3: The see-through plastic coolant recovery/overflow tank is usually mounted to the left fender skirt



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Fig. Fig. 4: When equipped, the cooling system should be topped off using the recovery tank

COOLING SYSTEM INSPECTION



Checking the Radiator Cap Seal

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 and the engine will overheat.

Worn caps should be replaced with a new one.

Checking the Radiator for Debris

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.

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.

DRAINING AND REFILLING THE SYSTEM



See Figures 5, 6 and 7


CAUTION
To avoid injuries from scalding fluid and steam, DO NOT remove the radiator cap while the engine and radiator are still HOT.

  1. Make sure the engine is cool and the vehicle is parked on a level surface, then remove the radiator neck cap and, if equipped, the recovery tank cap in order to relieve system pressure.
  2.  
  3. Position a large drain pan under the vehicle, then drain the existing antifreeze (coolant) by opening the radiator petcock and, if necessary, by removing the engine block drain plug(s). It its also possible to drain the system by disconnecting the lower radiator hose from the bottom radiator outlet.
  4.  



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Fig. Fig. 5: ONLY remove the cap from the radiator filler neck when the engine is COLD



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Fig. Fig. 6: Sometimes the radiator drain cock is positioned so coolant will run onto the radiator support and drip from various points (making quite a mess)



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Fig. Fig. 7: One easy solution is to use a funnel such as this one made from a plastic milk jug (recycling at its best)

  1. Close the radiator/engine drains or reconnect the lower hose.
  2.  
  3. If necessary, empty the coolant reservoir and flush it. This is most easily done by removing the reservoir tank from the vehicle.
  4.  
  5. Determine the capacity of your coolant system (see capacities specifications). Through the radiator filler neck, add a 50/50 mix of quality antifreeze (ethylene glycol) and water to provide the desired protection.
  6.  
  7. Leave the radiator pressure cap off, then start and run the engine until the thermostat heats up and opens, this will allow air to bleed from the system and provide room for additional coolant to be added to the radiator.
  8.  
  9. Add additional coolant to the radiator, as necessary, until the level is within 2 in. (51mm) of the radiator's filler neck base.
  10.  
  11. Stop the engine and check the coolant level.
  12.  
  13. Check the level of protection with an antifreeze tester, then install the radiator pressure cap.
  14.  
  15. If equipped with a coolant recovery/overflow tank, add coolant to the tank, as necessary, to achieve the proper level.
  16.  
  17. Start and run the engine to normal operating temperature, then check the system for leaks.
  18.  

FLUSHING AND CLEANING THE SYSTEM



The cooling system should be drained, thoroughly flushed and refilled at least every 30,000 miles or 3 months. These operations should be done with the engine cold, especially if a backpressure flushing kit is being used. Completely draining, flushing and refilling the cooling system at least every two years will remove accumulated rust, scale and other deposits. Coolant in late model vehicles is a 50/50 mixture of ethylene glycol and water for year round use. Use a good quality antifreeze with water pump lubricants, rust inhibitors and other corrosion inhibitors along with acid neutralizers.

There are many products available for cooling system flushing. If a backpressure flushing kit is used, it is recommended that the thermostat be temporarily removed in order to allow free flow to the system with cold water. Always follow the kit or cleaner manufacturer's instructions and make sure the product is compatible with your vehicle.

  1. Make sure the engine is cool and the vehicle is parked on a level surface, then remove the radiator neck cap and, if equipped the recovery tank cap in order to relieve system pressure.
  2.  
  3. Position a large drain pan under the vehicle, then drain the existing antifreeze and coolant by opening the radiator petcock and/or engine drains. It is also possible to drain the system by disconnecting the lower radiator hose, from the bottom radiator outlet.
  4.  
  5. Close the radiator/engine drains or reconnect the lower hose, as applicable and fill the system with water.
  6.  
  7. Add a can of quality radiator flush.
  8.  
  9. Idle the engine until the upper radiator hose gets hot and the thermostat has opened. This will allow the solution to fully circulate through the system.
  10.  
  11. Drain the system again.
  12.  
  13. Repeat this process until the drained water is clear and free of scale.
  14.  
  15. Close all drains and connect all the hoses.
  16.  
  17. If equipped with a coolant recovery system, flush the reservoir with water and leave empty.
  18.  
  19. Determine the capacity of your coolant system (see capacities specifications). Through the radiator filler neck, add a 50/50 mix of quality antifreeze (ethylene glycol) and water to provide the desired protection.
  20.  
  21. Leave the radiator pressure cap off, then start and run the engine until the thermostat heats up and opens, this will allow air to bleed from the system and provide room for additional coolant to be added to the radiator.
  22.  
  23. Add additional coolant to the radiator, as necessary, until the level is within 2 in. of the radiator's filler neck base.
  24.  
  25. Stop the engine and check the coolant level.
  26.  
  27. Check the level of protection with an antifreeze tester, then install the radiator pressure cap.
  28.  
  29. If equipped with a coolant recovery/overflow tank, add coolant to the tank, as necessary to achieve the proper level.
  30.  
  31. Start and run the engine to normal operating temperature, then check the system for leaks.
  32.  

 
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