DRAIN AND REFILL

The engine coolant should be drained and the system flushed periodically. (Please refer to the recommended maintenance interval charts in this section.) New coolant mixed with the proper amount of clean water should be used, since antifreeze eventually becomes corrosive. While draining and refilling may only be required every 30 months/30,000 miles (48,309 km), the coolant should be inspected at 15 months/15,000 miles (24,155 km) and replaced if it shows signs of rust or corrosion. Good coolant appears in its original color, while coolant that is permitting corrosion will appear cloudy and darker than its original color.

Complete draining and refilling of the cooling system will remove accumulated rust, scale and other deposits. To make the job easier, park your car close to a faucet or other source of water and run a garden hose to the radiator.

1. With the engine cold, remove the radiator cap and air bleeder plug. (Air bleeder plugs are only installed on the RX-7.)

   CAUTION
   When draining 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.

2. Drain the existing antifreeze/coolant into a suitable drain pan by opening the radiator and engine drain petcocks, or by disconnecting the bottom radiator hose at the radiator outlet. Before opening the radiator petcock, spray it with some penetrating lubricant, if necessary.

   NOTE: On 1979–85 RX-7s, coolant is drained by removing the drain plug in the intermediate engine housing and by disconnecting the lower radiator hose. On 1986–89 RX-7s, coolant is drained by removing the intermediate housing drain plug and opening the radiator drain cock.

3. Detach the hose at the base of the expansion tank (coolant recovery reservoir), and drain the old coolant into a suitable drain pan. Rinse the inside of this tank with clean water, if necessary, and reattach the hose.

   NOTE: In order to drain the expansion tank, it may be helpful to temporarily remove it from the vehicle.

   Fig. 3: On RX-7 models, remove the drain plug from the intermediate engine housing

   Fig. 4: After flushing the system and closing the drain plug(s), properly refill the system using a proper mixture of antifreeze/coolant and water

4. Set the heater control to the MAXIMUM heat position.
5. Flush the cooling system with clean water. (Directions for flushing and cleaning the system follow.)
6. Close the drain cocks or reinstall the drain plugs.

   Fig. 5: Drain and refill the coolant in the expansion tank

   Fig. 6: Use an antifreeze tester, such as this syringe type, to test the level of protection

7. Fill the cooling system with the proper amount and mixture of ethylene glycol or other aluminum-compatible coolant and water. Be sure to also add a fresh coolant mixture to the expansion tank. (The expansion tank and windshield washer fluid reservoir may be part of a dual reservoir; if so, be careful not to mix these two different types of fluid.)

   CAUTION
   Do not use alcohol or methanol-based coolants!

8. Run the engine at idle with the radiator cap removed to allow all the air to bleed out of the system. Add coolant as necessary to attain the proper level.
9. Install the radiator cap and the air bleeder plug (if equipped).
10. Check the level of protection with an antifreeze tester.
11. Start the engine and inspect for leaks.