🔧 Regal - Thermostat Replacement

The thermostat controls engine temperature by regulating coolant flow. If it’s stuck open you’ll get slow warm-up and poor heat; if it’s stuck closed you can overheat quickly. On your Regal, the thermostat is part of a housing assembly and you’ll drain/refill coolant as part of the job.

Difficulty Level: Intermediate | Estimated Time: 1.5-3 hours

Assumption: 2.0L turbo uses a thermostat/housing assembly with an O-ring seal.

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⚠️ Safety & Precautions

• ⚠️ Never open the coolant cap hot; let the engine cool fully.
• ⚠️ Support the car with jack stands; never rely on a jack alone.
• ⚠️ Coolant is toxic; keep away from kids/pets and clean spills fast.
• ⚠️ Avoid spilling coolant on the serpentine belt; it can slip.
• Disconnecting the battery is not required, but keep tools away from the alternator positive terminal.

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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 2 gallons)
• Funnel with long neck
• Trim clip removal tool
• Flathead screwdriver
• 7mm socket
• 8mm socket
• 10mm socket
• 13mm socket
• 3/8" drive ratchet
• 3/8" drive extension (6")
• Torque wrench (inch-pound)
• Hose clamp pliers
• Picks or hook tool set
• Shop towels

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Thermostat housing assembly - Qty: 1
• Thermostat housing O-ring/seal - Qty: 1
• Dex-Cool coolant (50/50 premix) - Qty: 2-3 gallons
• Replacement hose clamps - Qty: 1-3

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📋 Before You Begin

• Park on level ground, set the parking brake, and chock the rear wheels.
• Let the engine cool completely (radiator hoses should feel cool).
• Set the HVAC to the hottest setting later during bleeding (this opens the heater circuit).
• Raise the front of the car with a floor jack and support it with jack stands.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Relieve pressure and prep for draining

• Put on safety glasses and nitrile gloves.
• Slowly loosen the coolant surge tank cap by hand to relieve any leftover pressure, then remove it.
• Place a drain pan (at least 2 gallons) under the radiator area.

Step 2: Drain the coolant

• Remove the lower splash shield fasteners using a 7mm socket and trim clip removal tool.
• Open the radiator drain (petcock) using a flathead screwdriver, and let coolant drain into the pan.
• Tip: Aim the stream with cardboard.

Step 3: Remove the air intake ducting (access)

• Loosen intake clamps using a 7mm socket or flathead screwdriver.
• Unclip/remove the intake duct and set it aside.
• If needed, remove the engine cover by pulling straight up by hand.

Step 4: Locate the thermostat housing

• The thermostat housing sits at the front/side of the engine where the upper radiator hose connects.
• Follow the large radiator hose from the radiator back to the engine to find the housing.

Step 5: Disconnect hoses and electrical connector

• Use hose clamp pliers to compress the clamp(s), then slide them back on the hose.
• Twist the hose gently to break it loose, then pull it off the housing.
• If the housing has a sensor/heater connector, unplug it by hand (push the tab, then pull).
• Tip: Don’t pry on plastic nipples.

Step 6: Remove the thermostat housing

• Remove the housing bolts using a 10mm socket, 3/8" ratchet, and 6" extension.
• Pull the housing straight off. Expect more coolant to spill—keep the drain pan underneath.

Step 7: Clean the sealing surface

• Remove the old O-ring with a pick or hook tool set.
• Wipe the mating surface clean with shop towels. Do not gouge the aluminum surface.

Step 8: Install the new thermostat housing

• Install the new O-ring/seal onto the new housing (lightly wet it with clean coolant).
• Set the housing in place and hand-start all bolts to avoid cross-threading.
• Tighten housing bolts evenly using a torque wrench (inch-pound): Torque to 89 in-lbs (10 Nm).
• Tip: Snug in a crisscross pattern.

Step 9: Reconnect hoses and connector

• Reinstall hoses fully seated, then position clamps back in their original spots using hose clamp pliers.
• Reconnect any electrical connector until it clicks.

Step 10: Reinstall intake and splash shield

• Reinstall the intake duct and tighten clamps using a 7mm socket.
• Reinstall the lower splash shield using a 7mm socket and trim clip removal tool.
• Lower the car from the jack stands using the floor jack.

Step 11: Refill and bleed the cooling system

• Using a funnel with long neck, refill the surge tank with Dex-Cool coolant (50/50 premix) to the “FULL COLD” line.
• Start the engine and set HVAC to MAX HEAT with the fan on low.
• Let the engine idle and watch the coolant level; add coolant as the level drops.
• When the engine reaches normal temperature, confirm you have steady heat inside the cabin.
• Shut the engine off, let it cool, then recheck and top off to “FULL COLD.”

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✅ After Repair

• Check for leaks around the thermostat housing and hose connections with the engine running.
• Test drive 10–15 minutes, then recheck coolant level after a full cool-down.
• Verify the temperature gauge is stable and the heater works normally.
• If you get an overheating warning or no cabin heat, stop and re-bleed the system.

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💰 DIY vs Shop Cost

Shop Cost: $450-$900 (parts + labor)

DIY Cost: $60-$220 (parts only)

You Save: $230-$840 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 1.5-3 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.