Ford Thunderbird/Cougar 1983-1997 Repair Guide

Cooling System



When additional coolant is required to maintain the proper level, always add a 50/50 mixture of antifreeze/coolant and water.


See Figures 1 and 2

Exercise extreme care when removing the cap from a hot radiator. Wait a few minutes until the engine has time to cool somewhat, then wrap a thick towel around the radiator cap and slowly turn it counterclockwise to the first stop. Step back and allow the pressure to release from the cooling system. Then, when the steam has stopped venting, press down on the cap, turn it one more stop counterclockwise and remove the cap.

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Fig. Fig. 1: Cutaway view of a typical cooling system flow

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Fig. Fig. 2: Cooling systems should be pressure tested for leaks periodically

The coolant level in the radiator should be checked on a monthly basis, preferably when the engine is cold. On a cold engine, the coolant level should be maintained at one inch below the filler neck on vertical flow radiators, and 2 1 / 2 in. (63.5mm) below the filler neck at the COLD FILL mark on crossflow radiators. On the Coolant Recovery System, the level is maintained at the COLD LEVEL mark in the translucent plastic expansion bottle. Top up as necessary with a mixture of 50% water and 50% ethylene glycol antifreeze, to ensure proper rust, freezing and boiling protection. If you have to add coolant more often than once a month or if you have to add more than one quart at a time, check the cooling system for leads. Also check for water in the crankcase oil, indicating a blown cylinder head gasket.


See Figures 3, 4 and 5

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.

Completely draining and refilling the cooling system every two years at least will remove accumulated rust, scale and other deposits.

Use a good quality antifreeze with water pump lubricants, rust inhibitors and other corrosion inhibitors along with acid neutralizers. Use a permanent type coolant that meets specification ESE-M97B44A or the equivalent.

  1. Remove the radiator cap to relieve the pressure.

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Fig. Fig. 3: Remove the radiator cap

  1. Drain the existing antifreeze and coolant. Open the radiator and engine drain petcocks (models equipped), or disconnect the bottom radiator hose, at the radiator outlet. Set the heater temperature controls to the full HOT position.

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Fig. Fig. 4: Slowly turn the petcock at the bottom of the radiator to release the water/coolant mixture

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

  1. Close the petcock or reconnect the lower hose and fill the system with water.
  3. Add a can of quality radiator flush. If applicable, be sure the flush is safe to use in engines having aluminum components.
  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 the capacity specification chart). Add a 50/50 mix of quality antifreeze (ethylene glycol) and water to provide the desired protection.

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Fig. Fig. 5: While the engine is running, top off the coolant level

  1. After adding the appropriate amount of coolant and water, start the engine. Add more fluid to top off while the engine is running.


Most permanent antifreeze/coolant have a colored dye added which makes the solution an excellent leak detector. When servicing the cooling system, check for leakage at:

All hoses and hose connections
Radiator seams, radiator core, and radiator draincock
All engine block and cylinder head freeze (core) plugs, and drain plugs
Edges of all cooling system gaskets (head gaskets, thermostat gasket)
Transmission fluid cooler
Heating system components, water pump
Check the engine oil dipstick for signs of coolant in the engine oil
Check the coolant in the radiator for signs of oil in the coolant

Investigate and correct any indication of coolant leakage.

Check the Radiator Cap

See Figure 6

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Fig. Fig. 6: Be sure the rubber gasket on the radiator cap has a tight seal

While you are checking the coolant level, check the radiator cap for a worn or cracked gasket. If the cap doesn't seal properly, fluid will be lost and the engine will overheat.

A worn cap should be replaced with a new one.

Clean Radiator of Debris

See Figure 7

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Fig. Fig. 7: Periodically remove all debris from the radiator fins

Periodically clean any debris such as 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. Don't wiggle the fins back and forth too much. Straighten them once and try not to move them again.


A 50/50 mix of coolant concentrate and water will usually provide protection to -35°F (-37°C). Freeze protection may be checked by using a cooling system hydrometer. Inexpensive hydrometers (floating ball types) may be obtained from a local department store (automotive section) or an auto supply store. Follow the directions packaged with the coolant hydrometer when checking protection.