🔧 Altima - Thermostat Replacement

Replacing the thermostat on your Altima means draining some coolant, removing the thermostat housing, installing a new thermostat and seal, then refilling and bleeding the cooling system. The thermostat controls coolant flow through the engine, and a stuck thermostat can cause overheating, poor cabin heat, or slow warm-up.

Difficulty Level: Intermediate | Estimated Time: 2-3 hours

---

⚠️ Safety & Precautions

• ⚠️ Work only on a completely cold engine. Hot coolant can spray out and cause severe burns.
• ⚠️ Coolant is poisonous to people and pets. Catch it in a drain pan and wipe spills right away.
• ⚠️ Disconnecting the battery is recommended because you will be working near the engine cooling fans and wiring.
• ⚠️ Never open the radiator cap or coolant reservoir cap when the engine is hot.
• ⚠️ Support the vehicle with jack stands if raising the front. Never rely on a floor jack alone.

---

🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 12mm socket
• Ratchet wrench 3/8-inch drive
• Socket extension 6-inch 3/8-inch drive
• Flat-blade screwdriver 6-inch
• Pliers 8-inch
• Torque wrench 3/8-inch drive inch-pound range
• Coolant drain pan 2-gallon minimum
• Spill-free coolant funnel kit (specialty)
• Plastic scraper
• Shop towels
• Floor jack 2-ton minimum
• Jack stands 2-ton minimum
• Wheel chocks
• Nitrile gloves
• Safety glasses

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Engine thermostat - Qty: 1
• Thermostat housing seal/gasket - Qty: 1
• Nissan-compatible long-life coolant, blue premix 50/50 - Qty: 1-2 gallons
• Distilled water - Qty: 1 gallon

---

📋 Before You Begin

• 🅿️ Park your Altima on level ground, shift to Park, and set the parking brake.
• 🧊 Let the engine cool for several hours before opening the cooling system.
• 🛞 Place wheel chocks behind the rear wheels before raising the front.
• 🔋 Disconnect the negative battery cable with a 10mm socket. This reduces the chance of the cooling fans turning on unexpectedly.
• 📘 A thermostat is a temperature-controlled valve. It stays closed when the engine is cold and opens as the engine warms up.
• 🧰 A spill-free funnel locks onto the radiator or reservoir opening and helps remove trapped air from the cooling system.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Raise and Secure the Front

• Use wheel chocks behind the rear wheels.
• Use a floor jack 2-ton minimum at the front center jacking point to raise the front of your Altima.
• Place jack stands 2-ton minimum under the front support points and gently lower the car onto them.
• Put on safety glasses and nitrile gloves.
• Shake vehicle lightly to confirm stability.

Step 2: Disconnect the Battery

• Open the hood and locate the battery.
• Use a 10mm socket to loosen the negative battery terminal clamp.
• Move the negative cable away from the battery post so it cannot touch accidentally.

Step 3: Remove the Lower Engine Splash Shield

• Position the coolant drain pan 2-gallon minimum under the front of the engine area.
• Use a 10mm socket and ratchet wrench 3/8-inch drive to remove the lower splash shield fasteners.
• Use a flat-blade screwdriver 6-inch to gently release any plastic clips.
• Set the splash shield and fasteners aside in order.

Step 4: Drain the Coolant

• Make sure the engine is cold.
• Slowly loosen the coolant reservoir cap by hand to release any remaining pressure.
• Place the coolant drain pan 2-gallon minimum under the radiator drain area.
• Use pliers 8-inch or your hand to open the radiator drain cock if accessible.
• If the drain cock is difficult to reach, use pliers 8-inch to loosen the lower radiator hose clamp and carefully slide the hose back enough to drain coolant.
• Allow the coolant to drain until flow slows to a drip.
• Do not spill coolant on belts.

Step 5: Locate the Thermostat Housing

• Follow the lower radiator hose to where it connects to the engine.
• The metal or plastic cover at that connection is the thermostat housing.
• Use shop towels around the area to catch leftover coolant.

Step 6: Remove the Lower Radiator Hose from the Housing

• Use pliers 8-inch to compress the spring clamp on the lower radiator hose.
• Slide the clamp back along the hose.
• Twist the hose gently by hand to break it loose.
• If stuck, use a flat-blade screwdriver 6-inch carefully between the hose and neck to loosen the seal without cutting the hose.
• Pull the hose off the thermostat housing and aim it into the coolant drain pan 2-gallon minimum.

Step 7: Remove the Thermostat Housing

• Use a 12mm socket, socket extension 6-inch 3/8-inch drive, and ratchet wrench 3/8-inch drive to remove the thermostat housing bolts.
• Pull the housing straight away from the engine.
• Note the thermostat position before removing it. The new thermostat must face the same way.
• Remove the old thermostat and seal by hand.

Step 8: Clean the Sealing Surface

• Use a plastic scraper to clean the thermostat housing and engine mating surfaces.
• Use shop towels to wipe away old gasket material and coolant residue.
• Do not gouge the aluminum surface.
• Clean surfaces prevent leaks.

Step 9: Install the New Thermostat

• Install the engine thermostat in the same orientation as the old one.
• Install the thermostat housing seal/gasket onto the thermostat or housing as designed.
• If the thermostat has a small jiggle valve or bleed pin, position it upward when possible.
• A jiggle valve is a tiny loose pin that lets trapped air escape while filling coolant.

Step 10: Reinstall the Thermostat Housing

• Place the housing squarely against the engine by hand.
• Start all bolts by hand first to avoid cross-threading.
• Use a 12mm socket, socket extension 6-inch 3/8-inch drive, and ratchet wrench 3/8-inch drive to snug the bolts evenly.
• Use a torque wrench 3/8-inch drive inch-pound range to tighten the housing bolts evenly to Torque to 9.8 Nm (87 in-lbs).
• Do not overtighten small bolts.

Step 11: Reconnect the Lower Radiator Hose

• Push the lower radiator hose fully onto the thermostat housing neck by hand.
• Use pliers 8-inch to compress the spring clamp.
• Slide the clamp back into its original position behind the hose bead.
• Make sure the hose is not twisted or kinked.

Step 12: Close the Drain and Reinstall the Splash Shield

• Close the radiator drain cock by hand or with pliers 8-inch if used.
• If the lower hose was used for draining, confirm the hose and clamp are secure.
• Use a 10mm socket and ratchet wrench 3/8-inch drive to reinstall the lower splash shield.
• Snug the splash shield fasteners. Do not overtighten plastic fasteners.

Step 13: Refill the Cooling System

• Install the spill-free coolant funnel kit (specialty) on the coolant fill neck or reservoir opening.
• Fill with Nissan-compatible long-life coolant, blue premix 50/50.
• If using concentrate instead of premix, mix it 50/50 with distilled water before adding it.
• Fill slowly to reduce trapped air.

Step 14: Reconnect the Battery

• Reconnect the negative battery cable to the battery post.
• Use a 10mm socket to tighten the negative terminal clamp until secure.
• Do not overtighten the battery terminal.

Step 15: Bleed Air from the Cooling System

• Keep the spill-free coolant funnel kit (specialty) installed and partly filled.
• Start the engine and let it idle.
• Set the heater to maximum temperature and the blower to low.
• Watch for air bubbles coming up through the funnel.
• As the engine warms up, the thermostat will open and coolant level may drop. Add more coolant as needed.
• Use safety glasses and keep hands away from fans and belts.
• When bubbles stop and the heater blows warm air, install the cap using the funnel kit stopper.
• Air pockets can cause overheating.

Step 16: Check for Leaks

• Use a flashlight if available to inspect around the thermostat housing and lower radiator hose.
• Use shop towels to dry the area, then look for fresh coolant.
• If coolant leaks from the housing, shut the engine off and let it cool before correcting it.

Step 17: Lower the Vehicle

• Use the floor jack 2-ton minimum to raise your Altima slightly off the jack stands.
• Remove the jack stands 2-ton minimum.
• Lower the vehicle slowly with the floor jack 2-ton minimum.
• Remove the wheel chocks.

---

✅ After Repair

• ✅ Let the engine reach normal operating temperature and confirm the temperature gauge stays steady.
• ✅ Confirm the heater blows warm air at idle.
• ✅ After the first full heat-up and cool-down, recheck coolant level and top off with the correct coolant if needed.
• ✅ Check under your Altima for drips after the first drive.
• ✅ Dispose of used coolant at a recycling center or auto parts store. Do not pour it on the ground or into drains.

---

💰 DIY vs Shop Cost

Shop Cost: $250-$450 (parts + labor)

DIY Cost: $35-$90 (parts only)

You Save: $160-$360 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-2.5 hours.

---

🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.