Nissan Sentra/Pulsar/NX 1982-1996 Repair Guide

Cooling System



The cooling fluid or antifreeze, should be changed every 30,000 miles (48,309 km) or 24 months. When replacing the fluid, use a mixture of 50% water and 50% ethylene glycol or other compatible antifreeze.


See Figure 1

Check the coolant level every 3,000 miles (4,831 km) or once a month. In hot weather operation, it may be a good idea to check the level once a week. Check for loose connections and signs of deterioration of the coolant hoses. Maintain the coolant level 3 / 4 -1 1 / 4 in. (19-32mm) below the level of the filler neck when the engine is cold. If the engine is equipped with a coolant recovery bottle, check the coolant level in the bottle when the engine is cold; the level should be up to the MAX mark. If the bottle is empty, check the level in the radiator and refill as necessary, then fill the bottle up to the MAX level.

Never remove the radiator cap when the vehicle is hot or overheated. Wait until it has cooled. Place a thick cloth over the radiator cap to shield yourself from the heat and turn the radiator cap, SLIGHTLY, until the sound of escaping pressure can be heard. DO NOT turn any more; allow the pressure to release gradually. When no more pressure can be heard escaping, remove the cap with the heavy cloth, CAUTIOUSLY!

Never add cold water to an overheated engine while the engine is not running.

After filling the radiator, run the engine until it reaches normal operating temperature, to make sure that the thermostat has opened and all the air is bled from the system.


See Figures 1, 2, 3, 4 and 5

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Fig. Fig. 1: Always heed the warning on a radiator cap

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Fig. Fig. 2: Removing the inlet hose from the connector pipe

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Fig. Fig. 3: After filling the radiator, also fill the coolant reservoir

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Fig. Fig. 4: Using the 3-way valve to bleed the cooling system

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Fig. Fig. 5: Cooling system relief valve location-GA16I engine; others similar

To drain the cooling system, allow the engine to cool down BEFORE ATTEMPTING TO REMOVE THE RADIATOR CAP . Then turn the cap until it hisses. Wait until all pressure is off the cap before removing it completely.

To avoid burns and scalding, always handle a warm radiator cap with a heavy rag.

  1. At the dash, set the heater TEMP control lever to the fully HOT position.
  3. With the radiator cap removed, drain the radiator by loosening the petcock at the bottom of the radiator.

On the Sentra models, remove the heater inlet hose from the connector pipe at the left rear of the cylinder block to drain completely. After draining, reconnect the hose to the pipe.

  1. Close the petcock, then refill the system with a 50/50 mix of ethylene glycol or other compatible antifreeze; fill the system to 3 / 4 -1 1 / 4 in. (19-32mm) from the bottom of the filler neck. Reinstall the radiator cap.

If equipped with a fluid reservoir tank, fill it up to the MAX level.

  1. Operate the engine at 2,000 rpm for a few minutes and check the system for signs of leaks.

If the cooling system is not bled, air can be trapped in the cylinder head and cause engine damage when the engine heats up. Always bleed the cooling system after draining. The air has to escape from the highest point in the cooling system.

If you have replaced or repaired any cooling system component, the system must be bled. Insert a 3mm pin into the 3-way valve, located at the firewall, and push it in as far as it will go for early model vehicles. While pushing in on the pin, fill the radiator up to the filler opening. Replace the radiator cap and fill the reservoir. Loosen the plug in the upper part of the cylinder head for later model vehicles. If no plug or valve can be accessed, remove a cooling sender switch at the uppermost part of the cooling system. Fill the engine with coolant until it spills out of the removed sender. Install the sender and torque to 15 ft. lbs. (25 Nm).


To flush the system you must first, drain the cooling system but do not close the petcock valve on the bottom of the radiator. You can insert a garden hose, in the filler neck, turn the water pressure on moderately then start the engine. After about 10 minutes or less the water coming out of the bottom of the radiator should be clear. Shut off the engine and water supply, allow the radiator to drain then refill and bleed the system as necessary.

DO NOT allow the engine to overheat. The supply of water going in the top must be equal in amount to the water draining from the bottom, this way the radiator will always be full when the engine us running.

Usually flushing the radiator using water is all that is necessary to maintain the proper condition in the cooling system.

Radiator flush is the only cleaning agent that can be used to clean the internal portion of the radiator. Radiator flush can be purchased at virtually any auto supply store. Follow the directions on the label.