🔧 Gladiator - Thermostat Replacement

On your Gladiator, the thermostat is built into a thermostat housing assembly on the front of the engine. Replacing it fixes issues like overheating, slow warm-up, weak cabin heat, or coolant-temp related warning lights by restoring proper coolant flow control.

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

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⚠️ Safety & Precautions

• ⚠️ Let the engine cool completely before opening the cooling system.
• ⚠️ Never remove the coolant cap when hot; scalding coolant can spray out.
• ⚠️ Support the truck with jack stands if lifted; never rely on a floor jack.
• ⚠️ Keep coolant off paint, belts, and the driveway; it’s toxic to people and pets.
• ⚠️ Battery disconnect is not required, but keep tools away from the alternator power stud.

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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 liters)
• Funnel (spill-proof coolant funnel)
• Shop towels
• Ratchet (3/8" drive)
• 3/8" drive extension (6")
• 10mm socket
• Flathead screwdriver
• Hose clamp pliers
• Plastic trim clip tool
• Torque wrench (inch-pound)

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Thermostat housing assembly (includes thermostat and seal) - Qty: 1
• Engine coolant (OAT, 50/50 premix) - Qty: 2–3 gallons
• Distilled water - Qty: 1 gallon

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📋 Before You Begin

• 🅿️ Park on level ground, set the parking brake, and chock the rear wheels.
• 🧊 Make sure the engine is fully cool (top radiator hose should feel cool).
• 🧼 Put a drain pan under the front of the engine/radiator area.
• 🔥 Plan to set HVAC to full heat during bleeding (this helps push trapped air out).

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Make room to access the thermostat housing

• Remove the engine cover (if equipped) by pulling straight up by hand.
• Loosen the intake tube clamp(s) using a flathead screwdriver.
• Release any intake clips with a plastic trim clip tool, then move the intake tube/snorkel out of the way.

Step 2: Relieve pressure and drain coolant below the thermostat level

• Slowly loosen the coolant reservoir cap by hand to release any residual pressure, then remove it.
• Position a drain pan (at least 10 liters) under the radiator/lower hose area.
• Drain enough coolant so the level is below the thermostat housing (usually about 1–2 gallons). Use your vehicle’s drain point if accessible; otherwise, you can carefully slip the lower radiator hose off just enough to drain.
• Tip: Drain less first to avoid a huge mess.

Step 3: Remove the upper radiator hose from the thermostat housing

• Use hose clamp pliers to slide the clamp back away from the thermostat housing neck.
• Twist the hose gently to break it free, then pull it off.
• Aim the hose end into the drain pan (at least 10 liters) to catch any remaining coolant.

Step 4: Remove the thermostat housing assembly

• Place shop towels under the housing area to catch drips.
• Remove the thermostat housing mounting bolts using a 10mm socket, ratchet (3/8" drive), and 3/8" drive extension (6").
• Lift the thermostat housing assembly off the engine and keep the mating surface clean.

Step 5: Install the new thermostat housing assembly

• Wipe the engine mating surface clean using shop towels. Do not scratch the aluminum surface.
• Set the new thermostat housing assembly in place, making sure the seal stays seated.
• Start all bolts by hand, then snug them evenly using a 10mm socket.
• Final tighten with a torque wrench (inch-pound): Torque to 105 in-lb (12 Nm).

Step 6: Reconnect hoses and reinstall the intake parts

• Reinstall the upper radiator hose fully onto the thermostat housing neck.
• Use hose clamp pliers to return the clamp to its original position.
• Reinstall the intake tube/snorkel and tighten the clamp(s) using a flathead screwdriver.
• Reinstall the engine cover (if equipped) by pressing it down into place.

Step 7: Refill coolant and purge air

• Install a funnel (spill-proof coolant funnel) and fill with engine coolant (OAT, 50/50 premix) to the correct level.
• Start the engine and let it idle. Set HVAC to maximum heat and medium fan.
• As it warms up, watch the coolant level and add as needed through the funnel (spill-proof coolant funnel).
• When the radiator hose gets hot and you have steady heat from the vents, shut the engine off and let it cool fully.
• After cool-down, top off the reservoir to the proper mark and install the cap.
• Tip: A short drive helps purge tiny air pockets.

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✅ After Repair

• 🔍 With the engine running, check for leaks at the thermostat housing and hose connection.
• 🌡️ Test drive 10–15 minutes and confirm the temperature gauge stays normal.
• 🧊 After the next full cool-down, recheck coolant level and top off if needed.
• 🧾 If a warning light appears, scan codes and address any cooling-system faults.

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💰 DIY vs Shop Cost

Shop Cost: ₹10,000–₹22,000 (parts + labor)

DIY Cost: ₹3,000–₹9,000 (parts only)

You Save: ₹7,000–₹13,000 by doing it yourself!

Shop labor rates vary but typically run ₹800–₹2,000/hour. This repair takes a shop approximately 1.5–3.0 hours.

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🎯 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.