🔧 RX350 - Water Pump Replacement

The water pump circulates coolant through your engine and radiator. When it leaks or the bearing wears out, you can lose coolant, overheat, and risk engine damage—so replacing it promptly is important.

Difficulty Level: Advanced | Estimated Time: 3-5 hours

Assumption: 3.5L V6 uses the front-engine belt-driven water pump (most common setup).

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⚠️ Safety & Precautions

• ⚠️ Work only on a fully cool engine; hot coolant can cause severe burns.
• ⚠️ Support the RX350 with jack stands before working under it; never rely on a floor jack alone.
• ⚠️ Keep coolant off belts and pulleys; spills can cause belt slip and noise.
• ⚠️ Dispose of coolant properly; it’s toxic to people and animals.
• 🔌 Battery disconnect is not strictly required, but disconnecting the negative terminal helps prevent accidental starts while your hands are near the belt.

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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 3-gallon)
• Spill-free funnel kit
• Trim clip remover
• Flathead screwdriver
• 10mm socket
• 12mm socket
• 14mm socket
• 3/8" ratchet
• 3/8" torque wrench (10–80 ft-lbs range)
• Socket extension set (3" and 6")
• Serpentine belt tool with 14mm socket
• Pliers (hose clamp pliers)
• Plastic gasket scraper
• Shop rags
• Flashlight

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Water pump - Qty: 1
• Water pump gasket / O-ring (as equipped) - Qty: 1
• Toyota/Lexus Super Long Life Coolant (pink, pre-mixed) - Qty: 2 gallons
• Serpentine drive belt - Qty: 1
• Hose clamp (coolant hose, if any are damaged) - Qty: 1-2

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📋 Before You Begin

• Park on level ground, set the parking brake, and place wheel chocks behind the rear wheels.
• Let the engine cool completely (ideally overnight).
• Remove the plastic engine cover (pull upward) to improve access.
• Raise the front of the RX350 using a floor jack and support it with jack stands at the proper lift points.
• Place a drain pan under the radiator area for coolant draining.
• Tip: Take a quick photo of the belt routing.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the lower splash shield

• Use a trim clip remover and 10mm socket to remove the under-engine splash shield fasteners.
• Set the shield and clips/bolts aside in a small pile so nothing gets lost.

Step 2: Drain the engine coolant

• Remove the radiator cap only after the engine is cool (it releases pressure).
• Position the drain pan under the radiator drain cock.
• Open the drain cock by hand or with a flathead screwdriver as needed, and drain the coolant.
• Close the drain cock when finished (snug it—do not over-tighten).
• Tip: Keep pets away from drained coolant.

Step 3: Relieve serpentine belt tension and remove the belt

• Locate the belt tensioner (spring-loaded arm that keeps belt tight).
• Use a serpentine belt tool with 14mm socket to rotate the tensioner and release belt tension.
• Slide the belt off one pulley, then remove it completely.
• Definition: A “tensioner” is a spring-loaded pulley that keeps the belt tight.

Step 4: Remove the water pump pulley

• If the pulley bolts are hard to crack loose, you can briefly reinstall the belt to hold the pulley while loosening.
• Use a 10mm socket and 3/8" ratchet to remove the water pump pulley bolts.
• Remove the pulley and set it aside.

Step 5: Disconnect any hoses or brackets blocking the pump

• Inspect the area for any small coolant hose(s) or wiring brackets attached near the pump.
• Use pliers (hose clamp pliers) to compress spring clamps and slide them back on the hose.
• Carefully twist and pull the hose off (use a flathead screwdriver gently if stuck—don’t gouge the fitting).
• Use a 10mm socket or 12mm socket to remove any small bracket bolts if needed.

Step 6: Remove the water pump

• Place the drain pan under the water pump area (more coolant will spill here).
• Use a 10mm socket (and extension set as needed) to remove the water pump mounting bolts.
• Pull the pump straight off the engine.
• If it’s stuck, tap gently with the palm of your hand—do not pry aggressively on the aluminum surfaces.

Step 7: Clean the sealing surface

• Use a plastic gasket scraper to remove old gasket material or residue from the engine surface.
• Wipe clean with shop rags until the surface is smooth and dry.
• Tip: Don’t use metal scrapers on aluminum.

Step 8: Install the new water pump and gasket/O-ring

• Install the new gasket/O-ring onto the new pump (match the original orientation).
• Position the pump onto the engine, making sure it seats evenly.
• Hand-thread all bolts first to avoid cross-threading.
• Tighten the bolts evenly in a crisscross pattern using a 10mm socket.
• Torque to 10 Nm (89 in-lbs) using a 3/8" torque wrench.

Step 9: Reinstall the water pump pulley

• Install the pulley and start the bolts by hand.
• Use a 10mm socket to tighten evenly.
• Torque to 21 Nm (15 ft-lbs) using a 3/8" torque wrench.

Step 10: Reinstall hoses/brackets and install the new belt

• Reconnect any hose(s) removed and reposition the clamps using pliers (hose clamp pliers).
• Reinstall any brackets using a 10mm socket or 12mm socket.
• Route the new serpentine belt according to the under-hood routing diagram (or your photo).
• Use the serpentine belt tool with 14mm socket to rotate the tensioner and slip the belt onto the last pulley.
• Double-check that the belt ribs sit fully in every grooved pulley.

Step 11: Reinstall the splash shield

• Reinstall the under-engine splash shield using the trim clip remover (to seat clips) and 10mm socket for bolts.

Step 12: Refill and bleed the cooling system

• Lower the RX350 off the jack stands using the floor jack.
• Fill the radiator slowly with Toyota/Lexus Super Long Life Coolant (pink, pre-mixed) using a spill-free funnel kit.
• Start the engine and set the heater to HOT (this helps open coolant flow through the heater core).
• Let the engine idle and watch the coolant level in the funnel; add as needed.
• When the radiator fan cycles and heat blows consistently hot, shut the engine off and let it cool.
• Top off the radiator and the overflow reservoir to the “FULL” mark.
• Definition: “Bleeding” removes trapped air pockets from coolant.

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✅ After Repair

• Start the engine and inspect around the water pump for leaks with a flashlight.
• Verify the belt runs smoothly and quietly (no chirping or wandering).
• Test drive 10–15 minutes, then recheck coolant level after a full cool-down and top off if needed.
• Check the driveway/undertray the next morning for any fresh coolant drips.

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💰 DIY vs Shop Cost

Shop Cost: $700-$1,200 (parts + labor)

DIY Cost: $160-$350 (parts only)

You Save: $540-$850 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 3-5 hours.

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🎯 Ready to get started?

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