Ford Mustang 1989-1993 Repair Guide

Cooling System


See Figures 1 and 2

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Fig. Fig. 1: ALWAYS heed warning labels found in the engine compartment-this one include suggestions for safe cooling system service

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Fig. Fig. 2: Cut-away view of a typical cooling system flow

Never remove the radiator cap under any conditions while the engine is running! Failure to follow these instructions could result in damage to the cooling system and/or personal injury. To avoid having scalding hot coolant or steam blow out of the radiator, use extreme care when removing the radiator cap from a hot radiator. Wait until the engine has cooled, then wrap a thick cloth around the radiator cap and turn it slowly to the first stop. Step back while the pressure is released from the cooling system. When you are sure the pressure has been released, press down on the radiator cap (with the cloth still in position), turn and remove the cap.


See Figures 3 through 7

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Fig. Fig. 3: Coolant level should be monitored by periodically checking the coolant recovery tank

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Fig. Fig. 4: Small amounts of coolant should be added to the coolant recovery tank ...

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Fig. Fig. 5: ... a funnel helps reduce the mess

Any time you have the hood open, glance at the coolant recovery tank to make sure it is properly filled. Top of the cooling system using the recovery tank and its markings as a guideline. If you top off the system, make a note of it to check again soon. A coolant level that consistently drops is usually a sign of small, hard to detect leak, though in the worst case it could be a sign of an internal engine leak (blown head gasket/cracked block- ... check the engine oil for coolant contamination). In most cases, you will be able to trace the leak to a loose fitting or damaged hose (and you might solve a problem before it leaves you stranded). Evaporating ethylene glycol antifreeze will leave small, white (salt like) deposits, which can be helpful in tracing a leak.

At least annually or every 12,000 miles (19,000 km), all hoses, fittings and cooling system connections should be inspected for damage, wear or leaks. Hose clamps should be checked for tightness, and soft or cracked hoses should be replaced. Damp spots, or accumulations of rust or dye near hoses or fittings indicate possible leakage. These must be corrected before filling the system with fresh coolant. The pressure cap should be examined for signs of deterioration and aging. The fan belt and/or other drive belt(s) should be inspected and adjusted to the proper tension. Refer to the information on drive belts found earlier in this section. Finally, if everything looks good, obtain an antifreeze/coolant testing hydrometer in order to check the freeze and boil-over protection capabilities of the coolant currently in your engine. Old or improperly mixed coolant should be replaced.

When draining coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze, and are 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 coolant into a sealable container. Coolant may be reused unless it is contaminated or several years old.

At least once every 3 years or 36,000 miles (48,000 km), 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 won't protect against freezing.

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Fig. Fig. 6: If possible, pressure check the system at least once a year to help catch problems before something breaks

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Fig. Fig. 7: Use an antifreeze/coolant testing hydrometer to check the condition of the coolant in your engine

If you experience problems with your cooling system, such as overheating or boiling-over, check the simple before expecting the complicated. Make sure the system can fully pressurize (are all the connections tight/is the radiator cap on properly, is the cap seal intact-). Ideally, a pressure tester should be connected to the radiator opening and the system should be pressurized and inspected for leaks. If no obvious problems are found, use a hydrometer antifreeze/coolant tester (available at most automotive supply stores) to check the condition and concentration of the antifreeze in your cooling system. Excessively old coolant or the wrong proportions of water and coolant will hurt the coolant's boiling and freezing points.

Check the Radiator Cap

See Figure 8

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Fig. Fig. 8: 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 top doesn't seal properly, fluid will be lost and the engine will overheat. Worn caps should be replaced with a new one

Clean Radiator of Debris

See Figure 9

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Fig. Fig. 9: 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-nosed 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.


See Figures 10, 11, 12 and 13

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Fig. Fig. 10: The radiator petcock is usually the easiest method of draining the cooling system

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Fig. Fig. 11: The trickle of rust contaminated coolant suggests that this cooling system was neglected

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Fig. Fig. 12: For the most thorough cooling system draining, remove the engine block plug(s)

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Fig. Fig. 13: When the entire system is emptied, refilling must take place through the radiator opening (as opposed to the recovery tank)

A complete drain and refill of the cooling system at least every 30,000 miles (48,000 km) or 3 years will remove the accumulated rust, scale and other deposits. The recommended coolant for most late model cars is a 50/50 mixture of ethylene glycol and water for year-round use. Choose a good quality antifreeze with water pump lubricants, rust inhibitors and other corrosion inhibitors along with acid neutralizers.

  1. Drain the existing antifreeze and coolant. Open the radiator and engine drains (petcocks) or disconnect the bottom radiator hose at the radiator outlet. The engine block drain plugs can also be temporarily removed to drain coolant, but they are often hard to get at and it is not really necessary for this procedure.

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

  1. Close the petcock or reconnect the hose (and install any block drain plugs which may have been removed), then 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 any loose hoses.
  13. If equipped with a coolant recovery system, flush the reservoir with water and leave empty.
  15. Determine the capacity of the coolant system. (See the Capacities Specifications). Add a 50/50 mix of quality antifreeze 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 antifreeze/coolant hydrometer. Install the radiator cap and check for leaks.