GM Cadillac Deville_Fleetwood_ELD_Seville 1990-1998

Cooling System



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Fig. Cutaway view of a typical cooling system flow

When adding or changing the fluid in the system, be sure to maintain a 50 / 50 mixture of high quality ethylene glycol antifreeze and water in the cooling system. Use only antifreeze that is safe for use with an aluminum radiator.

Some GM Vehicles came equipped with a new silicate free anti freeze. This is called DEX-COOL®. There will be a label under the hood, in the area of the coolant bottle advising of this. DEX-COOL®was developed to last for 150,000 miles (240,000 km) or 5 years, whichever occurs first. Make sure only GM Goodwrench DEX-COOL® or equivalent is used when coolant is added or changed.

DO not use a solution stronger than 70% antifreeze. Pure antifreeze will freeze at -22°C (-8°F).


Check the coolant level in the recovery bottle or surge tank. The fluid level may be checked by observing the fluid level marks of the recovery tank. With the engine cold, the level should be at the FULL COLD or between the HOT and ADD level. When the engine is at normal operating temperatures, the coolant level should be at the HOT level. Only add coolant to bring the system to the proper level.

Should it he necessary to remove the radiator cap, make sure that the system has had time to cool, reducing the internal pressure.


The cooling system should be drained, thoroughly flushed, and refilled at least every 30,000 miles (48,000km) or 24 months. These operations should be done with the engine cold.

Most Cadillac engines today use GM Goodwrench DEX-COOL® or HAVOLINE® DEX-COOL® coolant. Check the maintenance charts for service intervals.

  1. Remove the radiator and recovery tank caps. Run the engine until the upper radiator hose gets hot. This means that the thermostat is open and the coolant is flowing through the system.
  3. Turn the engine OFF and place a large container under the radiator. Open the drain valve at the bottom of the radiator. Open the block drain plugs to speed up the draining process, if so equipped.
  5. Close the drain valves and add water until the system is full. Run the engine until hot. Repeat the draining and filling process several times, until the liquid is nearly colorless.
  7. After the last draining, fill the system with a 50 / 50 mixture of ethylene glycol and water. Run the engine until the system is hot and add coolant, if necessary. Replace the caps and check for any leak.

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Fig. The radiator drain is located on the left side of the radiator, under the lower radiator hose. It is difficult to reach, but easy to turn

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Fig. You may find it easier to drop the splash shield to give you more room to get access to the drain. Small pliers may be needed to turn the drain open

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Fig. The radiator cap gives you the warning about opening a hotcooling system. It also shows the pressure the system holds

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Fig. Removing the radiator cap to check the coolant level in the radiator

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Fig. Add coolant into the radiator

The Northstar uses a coolant solution and GM coolant supplement (sealant) designed for use in aluminum engines. These engines use DEX-COOL® and GM coolant supplement (sealant) P/N 3634621 (or equivalent) specifically designed for use in aluminum engines. Failure to use the engine coolant supplement (sealant) and the approved coolant antifreeze could result in major engine damage. When refilling the engine cooling system, add three pellets of engine coolant supplement sealant, GM Part No. 3634621 or equivalent and coolant antifreeze meeting GM specification 1825-M.