GM Corvette 1963-1982 Repair Guide

Cooling System


See Figures 1 and 2

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Fig. Fig. 1: Cooling systems should be pressure tested for leaks periodically

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Fig. Fig. 2: Cutaway view of a typical cooling system flow

Do not perform any coolant system services on a hot engine.

At least once every 2 years, 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 wont protect against freezing.

The pressure cap should be looked at 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.


See Figure 3

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Fig. Fig. 3: Be sure the rubber gasket on the radiator cap has a tight seal

While you are checking the coolant level, also check the condition of the radiator cap gasket and the seal inside of the cap (if your vehicle uses a coolant recovery system). The radiator cap is designed to seal the cooling system under normal operating conditions which allows the system to build-up a certain amount of pressure (this pressure rating is stamped or printed on the cap). The pressure in the system raises the boiling point of the coolant to help prevent overheating. If the radiator cap does not seal, the boiling point of the coolant is lowered and overheating will occur. If the cap must be replaced, purchase the new cap according to the type of system you have (with or without a coolant recovery tank) and the pressure rating which is specified for your vehicle.


See Figure 4

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Fig. Fig. 4: Periodically remove all debris from the radiator fins

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. Dont wiggle the fins back and forth too much. Straighten them once and try not to move them again.


See Figure 5

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Fig. Fig. 5: Remove the radiator drain plug (or open the petcock, if equipped), then drain the coolant into a container

Completely draining and refilling the cooling system every two years at least will remove accumulated rust, scale and other deposits. Coolant in late model cars is a 50-50 mixture of ethylene glycol and water for year round use. Use a good quality antifreeze with water pump lubricant, rust inhibitors and other corrosion inhibitors along with acid neutralizers.

  1. Drain the existing antifreeze and coolant. Open the radiator and engine drain petcocks, or disconnect the bottom radiator hose, at the radiator outlet.

Before opening the radiator petcock, spray it with some penetrating lubricant.

  1. Close the petcock or re-connect the lower hose and fill the system with water.
  3. Add a can of quality radiator flush.
  5. Idle the engine until the upper radiator hose gets hot.
  7. Drain the system again.
  9. Repeat this process until the drained water is clear and free of scale.
  11. Close all petcocks and connect all the hoses.
  13. If equipped with a coolant recovery system, flush the reservoir with water and leave empty.
  15. Determine the capacity of your cooling system (see capacities specifications). Add a 50/50 mix of quality antifreeze (ethylene glycol) and water to provide the desired protection.
  17. Run the engine to operating temperature.
  19. Stop the engine and check the coolant level.
  21. Check the level of protection with an anti-freeze tester, replace the cap and check for leaks.