🔧 Wrangler - Thermostat Replacement

Your thermostat helps your engine warm up quickly and then stay at the correct temperature. If it’s stuck open or closed, you can get no heat, overheating, or a check engine light. This job is mostly about careful coolant handling and sealing the housing correctly.

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

---

⚠️ Safety & Precautions

• ⚠️ Never open the radiator cap on a hot engine; hot coolant can spray and burn you.
• ⚠️ Support the front safely if you raise it; always use jack stands, not just a jack.
• ⚠️ Coolant is toxic—keep away from kids/pets and clean spills immediately.
• ⚠️ Dispose of used coolant properly (do not pour onto ground/drains).

---

🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Nitrile gloves
• Drain pan (at least 10-quart)
• Funnel
• Floor jack (rated 3-ton minimum)
• Jack stands (rated 3-ton pair minimum)
• Wheel chocks
• 3/8" drive ratchet
• 3/8" drive extension set
• 10mm socket
• Flat-blade screwdriver
• Hose clamp pliers
• Plastic scraper
• Shop towels
• Inch-pound torque wrench (specialty)

---

🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Engine thermostat (195°F / 90°C) - Qty: 1
• Thermostat seal / O-ring (if not included) - Qty: 1
• Engine coolant (HOAT, MS-9769 compatible) 50/50 premix - Qty: 2-3 gallons
• Upper radiator hose clamp (optional, if original is weak) - Qty: 1

---

📋 Before You Begin

• Park on level ground, set the parking brake, and chock the rear wheels.
• Let the engine cool fully (best: sit overnight).
• Set the HVAC to heat later during bleeding (heater core helps purge air).
• If you raise the front, lift with a floor jack and support with jack stands.

---

🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Relieve pressure safely

• Put on safety glasses and nitrile gloves.
• Slowly loosen the radiator cap by hand only when the engine is cold.
• Remove the coolant reservoir cap as well to help draining flow.

Step 2: Drain enough coolant

• Place a drain pan (at least 10-quart) under the radiator drain.
• Open the radiator drain cock using a flat-blade screwdriver (turn gently; it’s plastic).
• Drain about 1–2 gallons (enough so the level drops below the thermostat housing), then close the drain cock snugly by hand.

Step 3: Locate the thermostat housing

• Find the upper radiator hose (top hose). Follow it to the engine—where it meets the engine is the thermostat housing.
• Place shop towels under the housing to catch spills.

Step 4: Remove the upper radiator hose from the housing

• Compress the hose clamp using hose clamp pliers and slide the clamp back on the hose.
• Twist the hose gently to break it free, then pull it off the housing.
• If stuck, twist—don’t pry hard.

Step 5: Remove the thermostat housing

• Remove the housing bolts using a 10mm socket with a 3/8" drive ratchet and extension.
• Lift the housing off slowly—more coolant will spill into the towels/drain pan.

Step 6: Replace the thermostat and seal

• Note the thermostat orientation, then remove it by hand.
• Remove the old seal/O-ring.
• Clean both mating surfaces using a plastic scraper and shop towels. Do not gouge the aluminum.
• Install the new thermostat (same orientation as the original) and install the new seal/O-ring.

Step 7: Reinstall housing and torque bolts

• Set the housing in place and start both bolts by hand to avoid cross-threading.
• Tighten evenly using a 10mm socket.
• Final tighten with an inch-pound torque wrench (specialty) (a torque wrench is a tool that tightens bolts to an exact force so you don’t crack the housing): Torque to 12 Nm (105 in-lb).

Step 8: Reattach hose and clamp

• Slide the hose fully onto the housing.
• Reposition the clamp using hose clamp pliers so it sits over the hose bead.
• Wipe any spilled coolant using shop towels.

Step 9: Refill coolant

• Use a funnel to refill the radiator with HOAT, MS-9769 compatible 50/50 premix.
• Fill the coolant reservoir to the “FULL COLD” line.
• Reinstall the radiator cap.

Step 10: Bleed air from the cooling system

• Start the engine and set the heat to HOT.
• Let it idle until fully warm and you get steady heat from the vents.
• Watch the temperature gauge for normal operation and check for leaks at the housing and hose.
• Shut the engine off and let it cool completely, then top off the reservoir using a funnel if needed.

---

✅ After Repair

• Recheck coolant level the next morning (engine cold) and top off the reservoir if needed.
• Inspect for leaks after your first short drive (around the thermostat housing and upper hose).
• If the gauge runs hot, or you get no cabin heat, stop and recheck for trapped air and coolant level.

---

💰 DIY vs Shop Cost

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

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

You Save: $160-$400 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.

---

🎯 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.