🔧 Thermostat - Replacement

Your QX80’s thermostat controls engine warm-up and operating temperature. If it sticks closed you can overheat quickly; if it sticks open the engine may run cool and the heater can be weak. This job involves draining some coolant, swapping the thermostat in its housing, then refilling and bleeding air out.

Difficulty Level: Intermediate | Estimated Time: 1.5-3.0 hours

Assumption: stock cooling system with OEM-style thermostat housing.

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⚠️ Safety & Precautions

• ⚠️ Never open the radiator cap on a hot engine; let it cool completely.
• ⚠️ Coolant is toxic—keep it off skin/paint and away from kids/pets.
• ⚠️ Support the QX80 with jack stands if you go underneath; never rely on a jack.
• ⚠️ Keep hands/tools clear of the cooling fan; it can run unexpectedly.
• ⚠️ Battery disconnect is not required, but keep keys away from the vehicle while working near the fan.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• Floor jack (rated 3-ton minimum)
• Jack stands (rated 3-ton minimum)
• Wheel chocks
• Drain pan (at least 10-liter)
• Shop towels
• 10mm socket
• 12mm socket
• 3/8" drive ratchet
• 3/8" drive extension (6")
• Torque wrench (5–30 Nm range)
• Hose clamp pliers
• Flat-blade screwdriver
• Funnel
• Spill-free funnel kit (specialty)
• Pick tool (small)

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Engine coolant thermostat - Qty: 1
• Thermostat gasket / O-ring - Qty: 1
• Engine coolant (Nissan/INFINITI Blue SLLC premix) - Qty: 2-3 gallons
• Lower radiator hose clamp (optional, if original is weak) - Qty: 1

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📋 Before You Begin

• Park on level ground, set the parking brake, and chock the rear wheels.
• Let the engine cool fully (ideally overnight).
• Remove the plastic engine cover (pull up at the corners) if equipped.
• Set the HVAC to full HOT later during bleeding so coolant flows through the heater core.
• A torque wrench is a tool that tightens bolts to an exact spec so you don’t crack the housing.
• A spill-free funnel lets you fill and bleed air without burping coolant everywhere.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Raise the front (if needed) and remove the lower splash shield

• Use wheel chocks behind the rear tires.
• Lift the front with a floor jack (rated 3-ton minimum) and support with jack stands (rated 3-ton minimum).
• Remove the front under cover/splash shield using a 10mm socket and flat-blade screwdriver for any clips.
• Reinstall fasteners later to Torque to 10 Nm (7 ft-lbs) (plastic/cover fasteners only—snug, don’t strip).

Step 2: Drain coolant from the radiator

• Place a drain pan (at least 10-liter) under the radiator drain.
• Slowly remove the radiator cap on the radiator neck only if the engine is stone-cold (use nitrile gloves).
• Open the radiator drain cock using a flat-blade screwdriver (if slotted) and let coolant drain.
• Close the drain cock when done and Torque to 2 Nm (18 in-lbs) (lightly snug).
• Tip: Keep the drain pan centered—coolant streams shift.

Step 3: Access the thermostat area

• From the front of the engine bay, remove the intake duct if it blocks access using a flat-blade screwdriver (hose clamps).
• Locate the lower radiator hose where it meets the engine-side coolant inlet/thermostat housing (front-lower area of the engine).
• Use shop towels to protect belts/areas below from coolant drips.

Step 4: Remove the lower radiator hose from the thermostat housing

• Use hose clamp pliers to compress the clamp and slide it back on the hose.
• Twist the hose gently to break it free, then pull it off. Use a pick tool (small) carefully if it’s stuck (don’t gouge the plastic/metal neck).
• Catch remaining coolant with the drain pan.

Step 5: Remove the thermostat housing and thermostat

• Remove the thermostat housing bolts using a 10mm socket (some vehicles may use 12mm socket depending on housing fasteners).
• Separate the housing; expect coolant to spill—use shop towels.
• Remove the thermostat and old gasket/O-ring.
• Clean the mating surfaces with shop towels only; do not scrape aggressively.

Step 6: Install the new thermostat and gasket/O-ring

• Install the new thermostat in the same orientation as the old one.
• If the thermostat has a small “jiggle valve” air bleeder, position it at the top (12 o’clock) unless the part instructions specify otherwise.
• Install the new gasket/O-ring (do not reuse the old one).

Step 7: Reinstall the thermostat housing

• Start all bolts by hand to avoid cross-threading.
• Tighten evenly using a 10mm socket and then a torque wrench (5–30 Nm range).
• Torque to 9.8 Nm (87 in-lbs) for thermostat housing bolts.
• Tip: Even tightening prevents leaks and cracked housings.

Step 8: Reconnect the lower radiator hose

• Push the hose fully onto the housing neck.
• Use hose clamp pliers to move the clamp back into its original position.
• Wipe any coolant off with shop towels.

Step 9: Refill coolant and bleed air

• Install a spill-free funnel kit (specialty) on the radiator fill neck.
• Slowly add Nissan/INFINITI Blue SLLC premix using the funnel until the funnel level stabilizes.
• Start the engine and set HVAC to HOT and fan to medium.
• Let it idle; watch for air bubbles and keep the funnel level topped up.
• When the thermostat opens, the upper hose will get hot and coolant level may drop—add coolant as needed.
• Once bubbles stop and heat is steady, shut the engine off and let it cool completely, then remove the funnel and install the radiator cap.

Step 10: Reinstall splash shield and final top-off

• Reinstall the lower splash shield using a 10mm socket and flat-blade screwdriver.
• Fill the coolant reservoir to the MAX line using the funnel.
• After a full cool-down, recheck reservoir level and top off if needed.

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✅ After Repair

• Start the engine and confirm normal operating temperature on the gauge.
• Check for leaks around the thermostat housing and lower radiator hose with a flashlight.
• Verify the heater blows hot at idle (a common sign the system is bled properly).
• Over the next 2-3 drives, recheck the coolant reservoir level when cold and top off if it drops.
• Dispose of old coolant properly (do not pour on the ground).

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💰 DIY vs Shop Cost

Shop Cost: $350-$750 (parts + labor)

DIY Cost: $60-$180 (parts only)

You Save: $290-$570 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-3.0 hours.

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🎯 Ready to get started?

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