Autopapyrus · Nissan Largo (C23)
https://autopapyrus.com/guides/nissan/largo/cooling-system-bleeding-and-removing-air-from-the-heater-circuit/
https://autopapyrus.com/guides/nissan/largo/cooling-system-bleeding-and-removing-air-from-the-heater-circuit/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.
Nissan Largo (C23): Cooling System Bleeding and Removing Air from the Heater Circuit
An air pocket in the heater circuit shows up like this: the heater blows cold air with the engine warm, you hear gurgling inside the cabin, and the temperature gauge jumps around. It usually appears after replacing the coolant, radiator, hoses or water pump, or after topping off a low system. Air is removed with the engine warmed up, the front of the vehicle raised, and the heater set to maximum. The exact locations of the bleed points for your configuration (gasoline or diesel) are not documented in open sources, so a general procedure is given below.
Parts
2| № | Part |
|---|---|
| 01 | Antifreeze (coolant)for topping off; same type and color as what is in the system |
| 02 | Distilled waterif using concentrate |
Tools
5- funnel
- drain container
- gloves
- wrench or screwdriver for hose clamps
- jack stands or a jack if needed
Step by step
11 steps- Park the vehicle on level ground, shut off the engine and wait until it has cooled completely. Do not open the radiator cap or the expansion tank cap on a hot engine: the system is under pressure, and you could be burned by steam and hot coolant.
- If possible, raise the front of the vehicle on jack stands or drive the front wheels onto ramps. The radiator filler neck and the top of the system should be the highest point of the circuit. Place the stands under the structural body points, not under the lower control arms or plastic parts. Never work under a vehicle supported only by a jack.
- Remove the radiator cap (on models without a cap on the radiator, remove the expansion tank cap) and add coolant up to the filler neck. Fill the tank to the MAX mark.
- Inspect the engine bay: there may be bleed screws or fittings on the hoses and the thermostat housing. If there are any, loosen them a couple of turns (step 5).
- Set the cabin heater to maximum temperature, the fan to its lowest speed, and the airflow to the footwell. Start the engine with the radiator filler neck open and hold the revs at about 2000-2500 rpm until it warms up enough for the thermostat to open. You can tell by the hot upper radiator hose and by the level dropping in the filler neck.
- Watch the level in the filler neck. Bubbles will come out, the level will drop, and you will need to keep topping it off. As soon as a steady stream of coolant without foam comes out of the loosened screw, close it.
- Periodically raise the revs to 3000 rpm for 10-15 seconds and then release. This helps air escape from the engine block and the heater core. If the heater core's upper and lower hoses are accessible, you can carefully squeeze them by hand to push out the bubbles.
- When the heater is blowing hot, bubbles have stopped coming from the filler neck, and the radiator fan has cycled on at least once, top off to the proper level and close the radiator cap. Shut off the engine.
- Let the engine cool, then check the level in the expansion tank again. It should be between MIN and MAX. If the level has dropped, top it off.
- After 1-2 days of driving (after 2-3 heat-up and cool-down cycles), check the level once more, since residual air may escape along with the coolant. No torque is needed for the threaded fittings here: close the bleed screws hand-tight without force so you don't strip the threads.
- If the heater still doesn't warm up while the engine is hot and the upper hose is hot, check both hoses going to the heater core. If both are hot but the heater is cold, the cause may be the heater blend door or the heater valve rather than air. If one hose is hot and the other is cold, the heater core is clogged or still has an air pocket. In that case, flush the heater core or repeat the bleeding with the front of the vehicle raised higher.
Common mistakes and warnings
- Never open the radiator cap or unscrew the bleed screws on a hot engine: you could suffer a severe burn
- Coolant is toxic
- Do not leave it in open containers, and store it out of reach of children and pets
- If the coolant level keeps dropping with no visible leaks, or oil streaks appear in the coolant (or white smoke comes from the exhaust), the head gasket may be damaged
- In that case, it is best to go to a repair shop right away