GM Cadillac 1967-1989 Repair Guide

Cooling System



Coolant mixture in Cadillac is 50-50 ethylene glycol and water for year round use. Use a good quality antifreeze with water pump lubricants, rust inhibitors and other corrosion inhibitors along with acid neutralizers.


See Figures 1, 2, 3 and 4

It is best to check the coolant level when the engine and radiator are cool. Cadillac models covered in this guide are equipped with coolant recovery tanks connected by hoses to the radiator and mounted on the inner fender skirt. If the coolant level is at or near the FULL COLD (engine cold) or the FULL HOT (engine hot) lines on the tank, the level is satisfactory.

Never add coolant to a hot engine unless it is running; if it is not running, you risk cracking the engine block. The coolant recovery tank is the only accurate place to check the coolant level; however, coolant can be added to either the tank or directly to the radiator.

If you find the coolant level low, add a 50/50 mixture of ethylene glycol-based antifreeze and clean water. Do not add straight water unless you are out on the road and in emergency circumstances; if this is the case, drain the radiator and replenish the cooling system with an ethylene glycol mix at the next opportunity. Modern ethylene glycol antifreezes are special blends of anti-corrosive additives and lubricants that help keep the cooling system clean and help lubricate water pump bearings, which is why they are recommended by the manufacturers.

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Fig. Fig. 1: Common coolant flow path

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Fig. Fig. 2: Engine coolant reservoir

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Fig. Fig. 3: Removing the engine coolant reservoir cap

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Fig. Fig. 4: Adding engine coolant to reservoir


See Figures 5 and 6

The cooling system in your car accumulates some internal rust and corrosion in its normal operation. A simple method of keeping the system clean is known as flushing the system. It is performed by circulating a can of radiator flush through the system, and then draining and refilling the system with the normal coolant. Radiator flush is marketed by several different manufacturers, and is available in cans at auto departments parts stores, and many hardware stores. This operation should be performed every 30,000 miles or once a year.

To flush the cooling system:
  1. Drain the existing anti-freeze and coolant. Open the radiator and engine drain petcocks (located near the bottom of the radiator and engine block, respectively), or disconnect the bottom radiator hose at the radiator outlet.

Before opening the radiator petcock, spray it with some penetrating oil. Be aware that if the engine has been run, the coolant emptied will be HOT. DO NOT attempt to drain the cooling system until the temperature drops to a safe level.

  1. Close the petcock or re-connect the lower hose and fill the system with water-hot water if the system has just been run.

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. Add a can of quality radiator flush to the radiator or recovery tank, following any special instructions on the can.
  3. Idle the engine as long as specified on the can of flush, or until the upper radiator hose gets hot.
  5. Drain the system again. There should be quite a bit of scale and rust in the drained water.
  7. Repeat this process until the drained water is mostly clear.
  9. Close all petcocks and connect all hoses.
  11. Flush the coolant recovery reservoir with water and leave empty.
  13. Determine the capacity of your car's cooling system (see Capacities specifications in this guide). Add a 50/50 mix of ethylene glycol antifreeze and water to provide the desired protection.
  15. Run the engine to operating temperature, then stop the engine and check for leaks. Check the coolant level and top up if necessary.
  17. Check the protection level of your antifreeze mix with an antifreeze tester (a small, inexpensive syringe-type device available at any auto parts store). The tester has five or six small colored balls inside, each of which signify a certain temperature rating. Insert the tester in the recovery tank and suck just enough coolant into the syringe to float as many individual balls as you can (without sucking in too much coolant and floating all the balls at once). A table supplied with the tester will explain how many floating balls equal protection down to a certain temperature. For example, three floating balls might mean the coolant will protect your engine down to 5°F (-15°C).

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Fig. Fig. 5: Common radiator petcock

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Fig. Fig. 6: Washer fluid reservoir location - DO NOT BUT ENGINE COOLANT IN THIS RESERVOIR


See Figure 7

Anytime you check the coolant level, check the radiator cap as well. A worn or cracked gasket can mean improper sealing, which can cause lost coolant, lost pressure, and engine overheating (the cooling system is pressurized and the radiator cap has a pressure rating above the pressure of the system).

A worn cap should be replaced with a new one. Make sure the new cap has the proper pressure rating for your car's system; this is usually marked on the standard factory cap. You may want to go a few pounds per-square-inch over this rating, but never buy a cap having a rating less than the pressure of your car's system.

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Fig. Fig. 7: Check the cap for wear or cracks


See Figure 8

The efficiency of the radiator can be seriously impaired by blockage of the radiator fins. Leaves, insects, road dirt, paper-all are common obstacles to fresh air entering your radiator and doing its job.

Large pieces of debris, leaves and large insects can be removed from the fans by hand. The smaller pieces can be washed out with water pressure from a garden hose. This is often a neglected area of auto maintenance, so do a thorough job.

Bent radiator fins can be straightened carefully with a pair of needle-nose pliers. The fins are soft, so don't wiggle them, move them ONCE.

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Fig. Fig. 8: Keep the radiator fins clear of dirt and bugs for maximum cooling