GM Prizm/Nova 1985-1993 Repair Guide

Cooling System



See Figure 1

The correct coolant for the Nova and Prizm is any permanent, high quality ethylene glycol antifreeze mixed in a 50/50 concentration with water. This mixture gives the best combination of anti-freeze and anti-boil characteristics within the engine. Do not run the system filled with straight antifreeze or straight water; temperature extremes could damage the engine. For example, undiluted antifreeze will freeze at -8°F while a 50/50 mixture of antifreeze and tapwater freezes at -34°F.

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Fig. Fig. 1: The freezing protection rating can be checked with an antifreeze tester


See Figure 2

Always allow the car to sit and cool for an hour or so (longer is better) before removing the radiator cap. To avoid injury when working on a warm engine, cover the radiator cap with a thick cloth and turn it slowly counterclockwise until the pressure begins to escape.Never remove the radiator cap until the expansion tank cap is removed. After the pressure is completely removed, remove the cap. Never remove the cap until the pressure is gone.

It's best to check the coolant level when the engine is cold. The radiator coolant level should be between the LOW and the FULL lines on the expansion tank when the engine is cold. If low, check for leakage and add coolant up to the FULL line but do not overfill it. There must be room in the jug for normal expansion of hot fluids.

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Fig. Fig. 2: Check the coolant level in the expansion tank


The engine coolant should be changed every 30,000 miles or three years, whichever comes first. Replacing the coolant is necessary to remove the scale, rust and chemical by-products which build up in the system. This is a potentially messy job so have a large drain pan or bucket available along with a healthy supply of rags. Be prepared to deal with fluid spills immediately. See the previous list of Do's and Don'ts for other hints.

  1. Draining the cooling system is always done with the engine cold. Attempting to drain hot coolant is very foolish; you can be badly scalded.
  3. Remove the radiator cap.
  5. Position the drain pan under the drain cock on the bottom of the radiator. Additionally, the Nova/Prizm engines have a drain cock on the side of the engine block, near the oil filter. This should be opened to aid in draining the cooling system completely. If for some reason the radiator drain cock can't be used, you can loosen and remove the lower radiator hose at its joint to the radiator.
  7. If the lower hose is to be used as the drain, loosen the clamp on the hose and slide it back so it's out of the way. Gently break the grip of the hose on its fitting by twisting or prying with a suitable tool. Do not exert too much force or you will damage the radiator fitting. As the hose loosens, you can expect a gush of fluid to come out - be ready.Remove the hose end from the radiator and direct the hose into the drain pan. You now have fluid running from both the hose and the radiator.

Housepets and small animals are attracted to the odor and taste of engine coolant (antifreeze). It is a highly poisonous mixture of chemicals; special care must be taken to protect open containers and spillage.

  1. When the system stops draining, close both draincocks.
  3. In a bucket or similar large container, mix a 50/50 solution of antifreeze and water. Using a funnel, fill the radiator with this solution. Allow time for the fluid to run through the hoses and into the engine.
  5. Fill the radiator to just below the neck. With the radiator cap off, start the engine and let it idle; this will circulate the coolant and begin to eliminate air in the system. Top up the radiator as the level drops.
  7. When the level is reasonably stable, shut the engine off, and replace the radiator cap. Fill the expansion tank to a level halfway between the LOW and FULL lines and cap the expansion tank.
  9. Drive the car for 10 or 15 minutes; the temperature gauge should be fully within the normal operating range. It is helpful to set the heater to its hottest setting while driving - this circulates the coolant throughout the entire system and helps eliminate air bubbles.
  11. After the engine has cooled (2-3 hours), check the level in the radiator and the expansion tank, topping up as necessary.


Proceed with draining the system as outlined above. When the system has drained, reconnect any hoses close the radiator draincock. Move the temperature control for the heater to its hottest position; this allows the heater core to be flushed as well. Using a garden hose or bucket, fill the radiator and allow the water to run out the engine drain cock. Continue until the water runs clear. Be sure to clean the expansion tank as well.

If the system is badly contaminated with rust or scale,you can use a commercial flushing solution to clean it out. Follow the manufacturer's instructions. Some causes of rust are air in the system, failure to change the coolant regularly, use of excessively hard or soft water, and/or failure to use the correct mix of antifreeze and water.

After the system has been flushed, continue with the refill procedures outlined above. Check the condition of the radiator cap and its gasket, replacing the cap if anything looks improper.