Honda Accord/Civic/Prelude 1973-1983 Repair Guide

Cooling System



Use a quality, ethylene-glycol based engine coolant specifically recommended for use with vehicles utilizing aluminum engine parts that are in contact with the coolant. Note that some coolants, although labeled for use in such vehicles, actually may fail to provide effective corrosion protection; if necessary, consult a professional mechanic. It is best to buy a top quality product that is known to work effectively under such conditions. Always add coolant mixed with the proper amount of clean water. Never add either water or coolant alone. Mix the coolant at a 50:50 ratio, unless this will not provide sufficient freeze protection. Consult the chart on the antifreeze container and utilize the proportions recommended for the lowest expected temperatures in your area.


To check the coolant level, simply discern whether the coolant is up to the FULL line on the expansion tank. Add coolant to the expansion tank if the level is low, being sure to mix it with clean water. Never add cold water or coolant to a hot engine as damage to both the cooling system and the engine could result.

The radiator cap should be removed only for the purpose of cleaning or draining the system.

The cooling system is under pressure when Hot. Removing the radiator cap when the engine is warm or overheated will cause coolant to spill or shoot out, possibly causing serious burns. The system should be allowed to cool before attempting removal of the radiator cap or hoses.

If any coolant spills on painted portions of the body, rinse it off immediately.


The radiator coolant should be changed every 24,000 miles (1973-74 models), 30,000 miles (1975-80 models) or 45,000 miles (1981-83 models); thereafter, replace every 24 months or 30,000 miles. When following this procedure, be sure to follow the same precautions as detailed in the Coolant Level section.

  1. Remove the radiator cap.
  3. Slide a fluid catch pan under the radiator. Loosen the drain bolt at the base of the radiator and drain the radiator. If equipped, loosen the drain bolt on the drain cock on the side of the block.

When draining the coolant, keep in mind that cats and dogs are attracted by the 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 coolant in the reservoir tank by unclipping and disconnecting the hose.

In cold weather the thermostat may be closed; it may be necessary to remove the thermostat to completely drain the engine.

  1. Mix a solution of 50% ethylene glycol (designed for use in aluminum engines) and 50% clean water. Use a stronger solution, as specified on the antifreeze container, if the climate in your area demands it. Tighten the drain bolt(s) and refill the radiator all the way to the filler mouth. Reconnect the overflow tank connecting tube.
  3. Loosen the cooling system bleed bolt to purge air from the system. When coolant flows out of the bleed port, close the bolt and refill the radiator with coolant up to the mouth.
  5. To purge any air trapped in other parts of the cooling system, set the heater control to Hot , start the engine, set it to fast idle and allow it to reach normal operating temperatures. DO NOT tighten the radiator cap and leave the heater control in the Hot position. When the engine reaches normal operating temperatures, top off the radiator and keep checking until the level stabilizes; then, refill the coolant reservoir to the Full mark and make sure that the radiator cap is properly tightened.


See Figures 1 and 2

  1. Refer to the Thermostat, Removal & Installation'' procedures in Engine & Engine Overhaul and remove the thermostat from the engine.

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Fig. Fig. 1: Testing coolant condition with a tester

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Fig. Fig. 2: Removing and inspecting the radiator cap. Always check radiator when engine is cold

  1. Using a high pressure water hose, force fresh water into the thermostat housing opening, allowing the water to back-flush into the engine, heater and radiator. Back-flush the system until the water flowing from the radiator hose is clear.
  3. After cleaning, reverse the removal procedures. Refill the cooling system with fresh coolant.