2015 Isuzu NQR: Coolant Capacity & Type

The 2015 Isuzu NQR holds approximately 13.2 quarts (12.5 liters) of coolant.

Quick Answer

• Total Cooling System Capacity: 13.2 quarts (12.5 liters)
• OEM Coolant Specification: Isuzu Genuine LLC (Long Life Coolant), Red/Pink, Phosphate-enhanced OAT (P-OAT). Part Number: 2-9011Q-809-0
• Mix Ratio: 50/50 with distilled water (pre-mixed is recommended)

Capacity by Engine Option

The 2015 Isuzu NQR came equipped with a single engine option, the 5.2L 4HK1-TC turbocharged diesel engine.

Flush Interval

Following the correct flush interval is critical for the longevity of your NQR's cooling system, especially the water pump and EGR cooler.

• Normal Duty: Replace every 120,000 miles or 8 years, whichever comes first.
• Severe Duty: Replace every 60,000 miles or 4 years. Severe duty includes frequent short trips, heavy loads, extensive idling (as with PTO use), and operating in dusty or extreme temperature environments.

How to Refill & Bleed

Properly refilling and bleeding the air from the cooling system is crucial to prevent overheating and component damage. While a vacuum-fill tool is highly recommended for a complete, bubble-free fill, you can perform the procedure manually.

1. Mix Coolant: If using concentrate, mix it 50/50 with distilled water before pouring. Do not use tap water, as its mineral content can cause scaling and corrosion.
2. Slow Fill: With the engine cold, slowly pour the mixed coolant into the expansion tank (deaeration tank) until it reaches the "FULL" line.
3. Bleed Air: The 4HK1-TC engine has an air-bleed screw located on the thermostat housing. Loosen this screw as you fill to allow trapped air to escape. Tighten it once a steady stream of coolant flows out.
4. Run Engine: Start the engine with the heater on its highest setting. This circulates coolant through the heater core.
5. Top Off: As the engine warms up and the thermostat opens, the coolant level will drop. Continue to top off the expansion tank, keeping the level at the "FULL" mark.
6. Replace Cap & Check: Once the engine reaches operating temperature and the level stabilizes, replace the expansion tank cap. Let the truck cool down completely and re-check the level, topping off as necessary.

Common Cooling System Issues

The Isuzu N-Series trucks are known for their robust cooling systems, but some issues can arise, particularly as they age:

• EGR Cooler Failure: The Exhaust Gas Recirculation (EGR) cooler is a common failure point. A leaking EGR cooler can cause rapid coolant loss, white smoke from the exhaust, and potential engine damage if coolant enters the cylinders.
• Water Pump Leaks: The water pump may develop leaks from its weep hole or gasket over time. Look for coolant drips or pink/red crusty residue on the front of the engine block.
• Radiator Leaks: Leaks can develop in the plastic end tanks or the aluminum core of the radiator due to age, vibration, or impact damage.
• Thermostat Issues: A stuck thermostat (either open or closed) can cause the engine to overheat or fail to reach proper operating temperature, affecting performance and emissions.

Using the correct Isuzu-spec coolant and maintaining proper service intervals are the best ways to prevent these common problems.

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