🔧 Altima - Thermostat Replacement

The thermostat controls engine temperature by opening and closing coolant flow to the radiator. If it sticks closed, your Altima can overheat; if it sticks open, it may run too cool and heat poorly. You’ll drain some coolant, swap the thermostat at the engine’s coolant inlet, then refill and bleed air out.

Difficulty Level: Intermediate | Estimated Time: 2-4 hours

---

⚠️ Safety & Precautions

• ⚠️ Never open the radiator cap hot; let the engine cool fully.
• ⚠️ Coolant is toxic; keep it away from kids/pets and dispose properly.
• ⚠️ Use jack stands; never work under a car supported only by a jack.
• ⚠️ Your Altima is a hybrid: stay away from orange high-voltage cables/connectors and do not unplug any HV components.
• ⚠️ Keep hands/tools clear of belts/fans; the cooling fan can turn on unexpectedly.

---

🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• Wheel chocks
• Floor jack (rated 3-ton minimum)
• Jack stands (rated 3-ton minimum)
• Drain pan (at least 10-quart)
• Funnel
• Shop towels
• 10mm socket
• 12mm socket
• 3/8" ratchet
• 3/8" extension (6")
• Torque wrench (inch-pound, 30–250 in-lb range)
• Hose clamp pliers
• Pick tool
• Trim clip removal tool
• Plastic scraper

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Engine thermostat - Qty: 1
• Thermostat seal / O-ring - Qty: 1
• Engine coolant (Nissan Long Life / equivalent, premixed 50/50) - Qty: 2-3 gallons
• Hose clamp (lower radiator hose, optional if original is weak) - Qty: 1

---

📋 Before You Begin

• Park on level ground, set the parking brake, and place wheel chocks behind the rear tires.
• Let the engine cool completely (upper radiator hose should feel cool).
• Plan to capture coolant in a drain pan and keep it sealed.
• Tip: Take a photo of hose routing first.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Raise the front and remove the lower splash shield

• Use a floor jack (rated 3-ton minimum) to lift the front at the proper jacking point, then support with jack stands (rated 3-ton minimum).
• Use a trim clip removal tool and 10mm socket to remove the lower engine splash shield/undercover fasteners.

Step 2: Drain the coolant

• Place a drain pan (at least 10-quart) under the radiator drain.
• Slowly remove the radiator cap (only if completely cool).
• Open the radiator drain and let coolant drain into the pan.
• If flow is slow, use hose clamp pliers to loosen the lower radiator hose clamp slightly to help it drain (keep the hose seated until you’re ready for Step 3).

Step 3: Access the thermostat housing (coolant inlet)

• Follow the lower radiator hose to where it connects to the engine—this connection is the thermostat housing area.
• Use hose clamp pliers to slide the clamp back, then twist the hose gently to break it free.
• If the hose is stuck, use a pick tool carefully around the edge to loosen it without tearing the hose.

Step 4: Remove the thermostat housing

• Use a 12mm socket, 3/8" ratchet, and 3/8" extension (6") to remove the thermostat housing bolts.
• Pull the housing off slowly; more coolant will spill, so keep the drain pan underneath.
• Note the thermostat orientation before removal.

Step 5: Install the new thermostat and seal

• Remove the old thermostat and seal.
• Clean both mating surfaces using a plastic scraper and shop towels. (Mating surface = the flat surfaces that seal together.)
• Install the new thermostat with the new seal/O-ring. If your thermostat has a small “jiggle valve”/bleed pin, position it at the top (12 o’clock) unless your new part specifies otherwise.

Step 6: Reinstall the housing and hose

• Reinstall the thermostat housing bolts by hand first to avoid cross-threading.
• Use a torque wrench (inch-pound, 30–250 in-lb range) to tighten housing bolts evenly: Torque to 12 N·m (106 in-lb).
• Reinstall the lower radiator hose and position the clamp using hose clamp pliers.

Step 7: Reinstall the splash shield

• Use a 10mm socket and trim clip removal tool to reinstall the under-cover and clips/bolts.
• Lower the car using the floor jack (rated 3-ton minimum).

Step 8: Refill and bleed air from the cooling system

• Refill the radiator slowly using a funnel with engine coolant (premixed 50/50).
• Fill the coolant reservoir to the “MAX” line.
• Start the car and set the heater to HOT with the fan on medium/high. (This helps open the heater core so air can escape.)
• Let the engine reach operating temperature; watch for the upper radiator hose to get hot (thermostat opened).
• Shut the car off, let it cool, then recheck the radiator and reservoir and top off as needed.
• Tip: Squeeze hoses to burp trapped air.

---

✅ After Repair

• Check for leaks around the thermostat housing and lower radiator hose with the engine running.
• Verify cabin heat works normally and the temperature gauge stays steady.
• After your first short drive, let it cool and recheck coolant level again (radiator and reservoir).
• Clean any spilled coolant and keep the drained coolant in a sealed container for proper disposal.

---

💰 DIY vs Shop Cost

Shop Cost: $350-$700 (parts + labor)

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

You Save: $290-$520 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 2-3 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.