GM Full Size Vans 1987-1997 Repair Guide

Cooling System


See Figures 1 through 5

For most of the vans covered in this guide (except 1996-97 models), you should inspect, flush and refill the cooling system with fresh coolant (antifreeze) at least once every two years or 30,000 miles (48,000 km). If the coolant is left in the system too long, it loses its ability to prevent rust or corrosion. If the coolant has too much water, it won-t protect against freezing and can boil over in the summer.

The cooling systems for all 1996-97 models were originally filled at the factory with silicate-free DEX-COOL® coolant meeting GM specification 6277M. The fluid is easily identified because of its orange color (instead of the green that is normally associated with ethylene glycol antifreeze). If your cooling system is filled with DEX-COOL®, then no periodic service is required, other than fluid level checks, for 150,000 miles (240,000 km) or 5 years, whichever comes first. BUT if you add a silicate coolant to the system (even in small amounts), premature engine, heater core or radiator corrosion may occur. In addition, the coolant will have to be changed sooner (every 30,000 miles/48,000 km or 2 years, just like in vehicles not using DEX-COOL®).


The recommended coolant mixture for 1987-95 Chevy/GMC vans is 50/50 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. 1996-97 models were factory equipped with GM DEX-COOL® silicate-free coolant, which is easily identified by its orange color.GM does not recommend any other type of coolant for these vehicles.

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Fig. Fig. 1: The cooling system should be pressure tested once a year

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Fig. Fig. 2: Remove any debris from the radiator's cooling fins

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Fig. Fig. 3: Coolant condition can be checked with an inexpensive tester

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Fig. Fig. 4: Check the condition of the radiator cap gasket and seal

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Fig. Fig. 5: Inspect coolant for contamination


See Figure 6 through 12

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Fig. Fig. 6: Cutaway view of a typical cooling system flow

  1. Check the level on the see-through expansion tank.

The radiator coolant is under pressure when hot. To avoid the danger of physical harm, coolant level should be checked or replenished only when the engine is cold. To remove the radiator cap when the engine is hot, first cover the cap with a thick rag, or wear a heavy glove for protection. Press down on the cap slightly and slowly turn it counterclockwise until it reaches the first stop. Allow all the pressure to vent (indicated when the hissing sound stops). When the pressure is released, press down on the cap and continue to rotate it counterclockwise. Some radiator caps have a lever for venting the pressure, but you should still exercise extreme caution when removing the cap.

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Fig. Fig. 7: Coolant level can be measured against the marks on the side of the recovery reservoir ...

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Fig. Fig. 8: ... or by removing the radiator cap and viewing the level

  1. Check the level and, if necessary, add coolant through the expansion tank to the proper level. Use a 50/50 mix of ethylene glycol antifreeze and water on 1987-95 models and GM DEX-COOL® on 1996-97 models. Alcohol or methanol base coolants are not recommended. Antifreeze solutions should be used, even in summer, to prevent rust and to take advantage of the solution's higher boiling point compared to plain water. This is imperative on air conditioned vans; the heater core can freeze if it isn't protected. Coolant should be added through the coolant recovery tank, not the radiator filler neck.

Never add large quantities of cold coolant to a hot engine! A cracked engine block may result!

Each year the cooling system should be serviced as follows:

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Fig. Fig. 9: On 1996-97 models, labels in the engine compartment warn that a special coolant is used

Wash the radiator cap and filler neck with clean water.
Check the coolant for proper level and freeze protection.
Have the system pressure tested at 15 psi (103 kPa). If a replacement cap is installed, be sure that it conforms to the original specifications.
Tighten the hose clamps and inspect all hoses. Replace hoses that are swollen, cracked or otherwise deteriorated.
Clean the frontal area of the radiator core and the air conditioning condenser, if so equipped.

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Fig. Fig. 10: To replenish the cooling system, remove the recovery reservoir cap ...:

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Fig. Fig. 11: ... then, using a funnel, add coolant until it reaches the full mark on the side of the reservoir ...

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Fig. Fig. 12: ... or, the radiator cap can be removed and the coolant added there


The cooling system in your van accumulates some internal rust and corrosion during normal operation. A simple method of keeping the system clean is known as flushing the system. It is performed by circulating a can of radiator flush through the system, then draining and refilling the system with the recommended coolant and water mixture. Radiator flush is marketed by several different manufacturers, and is available in containers at many automotive departments, parts stores, and hardware stores. This operation should be performed every 30,000 miles (48,000 km) or once every 2 years for vehicles with silicate based coolant; every 150,000 miles (240,000 km) or once every 5 years for vehicles using GM DEX-COOL® coolant.

When draining the coolant, keep in mind that cats and dogs are attracted by ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

  1. Drain the existing antifreeze and coolant. Open the radiator and engine drain petcocks (located near the bottom of the radiator and engine block, respectively), or disconnect the bottom radiator hose at the radiator outlet.
  3. Close the petcock or reconnect the lower hose and fill the system with water - hot water if the engine is at operating temperature.
  5. Add a can of quality radiator flush to the radiator or recovery tank, following the instructions on the can.
  7. Idle the engine as long as specified on the can of flush, or until the upper radiator hose gets hot.
  9. Drain the system again. There should be quite a bit of scale and rust in the drained water.
  11. Refill the system with water and repeat the process (do not add additional radiator flush) until the drained water is mostly clear.
  13. Close all petcocks and connect all hoses.
  15. Flush the coolant recovery reservoir with water and leave empty.
  17. Determine the capacity of your van-s cooling system (see the Capacities specifications in this guide). Add the correct mixture AND TYPE of coolant - refer to the fluid recommendations in this section if you are unsure. Fill the radiator to about 1 / 2 in. (13mm) from the bottom of the filler neck.
  19. Start the vehicle and allow it to reach normal operating temperature. When the thermostat opens, air which was trapped in the engine will be expelled, causing the coolant level to drop. Add the correct type and mixture of coolant and water until the level reaches the bottom of the filler neck, then replace the radiator cap.
  21. Turn the vehicle off and add the same mixture and type of coolant to the recovery tank, but do not exceed the ADD or COLD marks on the side of the tank.
  23. Run the engine to operating temperature, then stop the engine and check for leaks. Check the coolant level and top up if necessary.
  25. Check the protection level of the coolant with an antifreeze tester (a small, inexpensive syringe type device available at auto parts stores). The tester has five or six small colored balls inside, each of which signify a certain temperature rating. Insert the tester in the recovery tank and suck just enough coolant into the syringe to float as many individual balls as you can (without sucking in too much coolant and floating all the balls at once). A chart provided with the tester will equate the number of floating balls with a certain temperature level of protection. For example, three floating balls might mean the coolant will protect your engine down to 5°F (-15°C).