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INSTALL INSTRUCTIONS: 5th Gen 4Runner (2010-2023) Transmission or Power Steering Cooler

⚠️ Read these instructions in full before starting the installation.Take your time and follow each step carefully for the best results.


BEFORE YOU BEGIN

✅ Park the vehicle on a flat, level surface.

✅ Disconnect the vehicle battery before starting the installation.

✅ Confirm all kit components are present (see packing slip)

✅ Verify you have additional Toyota WS Transmission Fluid or Power Steering Fluid (if installing as a steering cooler).


IMPORTANT REMINDERS

⚠️ Ensure the engine, transmission, and steering systems are cool before working.

⚠️ Properly support the vehicle if lifting it for access.

⚠️ Always wear proper PPE—safety glasses and gloves are required.

⚠️ Periodically inspect all hoses and clamps after installation, especially on long trips or during heavy use.


TOOLS & SUPPLIES NEEDED

  • Basic hand tools (sockets, wrenches)

  • Ratchet with extensions

  • Flathead screwdriver

  • Pliers

  • Hose cutter or sharp utility knife

  • Toyota WS Transmission Fluid or Power Steering Fluid

  • Drain pan

  • Funnel

  • Zip ties (optional for hose management)

  • Clean rags


STEP-BY-STEP INSTALLATION INSTRUCTIONS

STEP 1: Remove the Plastic Front Bumper Cover

  • Park the vehicle on a flat, level surface.

  • Disconnect the vehicle battery (positive and negative terminals).

  • Remove the 10mm bolts and plastic clips:

    • At the top of the grille

    • At the bottom of the bumper

    • Inside the fender liners

  • If you have a steel bumper, only remove the plastic cover.

  • Gently release the bumper clips and pull the plastic bumper cover away from the vehicle.

  • Set the bumper cover aside on a soft surface to avoid damage.


STEP 2: Confirm Fan Orientation

  • Connect 12v power to the fan and observe airflow direction.

  • The fan must push air from the front of the vehicle through the cooler toward the rear.

  • Some coolers may arrive with the fan blades flipped and polarity reversed. Confirm and adjust as needed.


How to Check:

  1. Connect 12v power to the blue wire and ground to the black wire.

  2. If the fan pushes air toward the front of the vehicle, reverse the polarity by connecting 12v power to black and ground to blue.


If Polarity Needs Reversing:

  1. Remove the four screws holding the fan assembly to the cooler.

  2. Remove the fan blade from the motor shaft.

  3. Flip the fan blade and reinstall it onto the motor shaft.

  4. Reattach the fan to the cooler with the four screws.

  5. For most installations, use the third hole from the top on the bracket to bolt through the topmost hole on the cooler.

  6. Align the Mishimoto cooler with the bracket, secure using the supplied screws, and tighten snugly (do not overtighten).

  7. Confirm proper alignment before proceeding.


STEP 3: Mount the Cooler Assembly

  • Remove the plastic cover above the hood latch mechanism.

  • Remove the two 12mm bolts holding the horn.

  • Position the cooler assembly onto the radiator support.

  • Use the supplied longer M8 bolts and aluminum spacers to mount both the horn and cooler assembly to the radiator support.

  • Install the lower M6 bolt and check for clearances.

  • Tighten bolts snugly but do not overtighten.


Clearance Notes:

  • Ensure there is proper clearance between body-mounted components (radiator support, cooler assembly) and frame-mounted components (metal bumper, winch mount).

  • Depending on your setup:

    • Move the cooler up or down on the bracket.

    • Mount the cooler behind the bracket if needed for additional clearance.


Before reinstalling the hood latch cover:

  • Trim to fit cleanly around the cooler and bracket.

  • Ensure the cover does not interfere with the cooler, bracket, or hoses.


STEP 4: Wire the Cooler Fan

  • Wire the fan using one of the following options:

    1. Directly to a switch panel (user-controlled)

    2. Through a standalone fan wiring harness

    3. With Mishimoto’s temperature-controlled harness

  • Refer to Mishimoto’s instructions for wiring and temperature sensor setup.


CHOOSE YOUR INSTALLATION PATH

✅ If installing as a Transmission Cooler → Proceed to Steps 4A–6A

✅ If installing as a Power Steering Cooler → Proceed to Steps 4B–6B


TRANSMISSION COOLER INSTALLATION

STEP 4A: Hose Routing and Installation

⚠️ Important Notes:

  • Do not bypass the OEM radiator. It preheats transmission fluid when cold and acts as a fluid reserve.

  • Bypassing the OEM radiator may result in improper fluid temperature regulation, especially in colder climates.

Routing & Installation

  1. Remove the short OEM rubber hose (approx. 8") from the bottom driver side of the radiator.

  2. Route a new hose from the bottom driver side radiator fitting, through the holes in the radiator support, to the lower fitting on the Mishimoto cooler.

    • Measure and cut hose to length (smooth bends, no kinks).

    • Pre-install hose clamps before connecting.

    • Connect both ends and tighten clamps securely.

  3. Use the remaining hose to connect the upper fitting on the Mishimoto cooler to the OEM hardline where the other end of the soft line was connected.

    • Measure, cut, pre-install clamps, and connect securely.

  4. Secure hoses with zip ties, keeping them clear of hot surfaces (headers, exhaust) and moving parts (fans, pulleys).

  5. Install the rubber trim lock around sharp edges on the holes in the radiator support to protect hoses.

  6. Confirm all hose routing and clamp tightness.


STEP 5A: Refill & Cycle the Transmission System

Follow Toyota service manual procedures for checking and setting the transmission fluid level. Improper fluid level can lead to transmission damage or failure.


Toyota Service Manual Fluid Level Procedure:

  1. Warm Up the Transmission

    • Start the engine and idle until transmission fluid reaches 104°F to 113°F (40°C to 45°C).

    • Use an OBD-II scanner (or ScanGauge II) to monitor fluid temperature.

  2. Cycle Through All Gears

    • With the brake pedal pressed, shift through all positions (P, R, N, D).

    • Pause in each position, then return to Park (P).

  3. Raise the Vehicle

    • Ensure the vehicle is level.

    • Raise and secure it on jack stands or a lift.

  4. Remove the Overflow/Check Plug (Engine Running)

    • Locate the transmission overflow/check plug on the pan.

    • Remove it with the engine running and transmission at the correct temperature.

  5. Assess Fluid Level

    • If fluid drips, the level is correct.

    • If no fluid comes out, add Toyota WS transmission fluid through the fill plug until it drips.

    • If a steady stream pours out, let it drain until it slows to a drip.

  6. Reinstall the Overflow/Check Plug

    • Tighten the plug once fluid drips steadily at the correct temperature.

  7. Lower the Vehicle & Perform Final Check

    • Lower the vehicle and perform a short test drive.

    • Recheck fluid levels and inspect for leaks.

⚠️ IMPORTANT: If you are not comfortable performing this procedure, contact a professional shop for installation and fluid level setting. Improper fluid level or installation can result in transmission failure.


POWER STEERING COOLER INSTALLATION


STEP 4B: Hose Routing and Installation


STEP 1: Remove the Factory Power Steering Cooler Hardline

  • Remove the factory thick hardline power steering cooler that is mounted in front of the radiator.

  • This line is often in the way of winch or high-clearance bumper installs, which is another reason to upgrade to this Mishimoto cooler system.


STEP 2: Choose Your Hose Routing Option

You have two routing options depending on your setup:


Option 1: Connect Directly to the Hardlines

  1. Route a hose from the driver side hardline (near the front bumper mount) to the bottom fitting on the Mishimoto cooler.

  2. Route another hose from the passenger side hardline to the top fitting on the Mishimoto cooler.

  3. Measure and cut both hoses to length (smooth bends).

  4. Pre-install hose clamps before connecting.

  5. Connect hoses to fittings and tighten clamps securely.

  6. Install the rubber trim lock around sharp edges in the radiator support.

  7. Secure hoses with zip ties away from hot surfaces and moving parts.


Option 2: Eliminate the Factory Hardlines

Additional hose may be required.

  1. Route a hose from the return fitting on the steering rack to the bottom fitting on the Mishimoto cooler.

  2. Route another hose from the top fitting on the Mishimoto cooler to the smaller return fitting on the power steering fluid reservoir.

  3. Measure and cut both hoses to length.

  4. Pre-install hose clamps before connecting.

  5. Connect hoses to fittings and tighten clamps securely.

  6. Install the rubber trim lock around sharp edges in the radiator support.

  7. Secure hoses with zip ties away from hot surfaces and moving parts.


STEP 5B: Refill & Cycle the Power Steering System

  1. Top off power steering fluid.

  2. Turn the steering wheel lock to lock at least 20 times, or more if you completely bypassed all the factory hardlines (Option 2).

    • This helps remove air from the system.

  3. If possible, lift the front wheels off the ground to make cycling the steering easier.

  4. Start the vehicle and continue cycling the steering lock to lock to fully bleed the system.

  5. Recheck fluid level and top off as needed.


FINAL STEPS (APPLY TO BOTH INSTALLATIONS)


STEP 6: Reinstall the Front Bumper

  • Check for leaks one last time before reinstalling bumper.

  • Carefully guide the bumper back into place, ensuring hoses are not pinched or kinked.

  • Reattach all plastic clips, 10mm bolts, and any othe components removed earlier.

  • Verify bumper alignment and fitment.


STEP 7: Test Drive & Final Inspection

  • Start the engine and let it idle.

  • Cycle through all transmission gears (if transmission cooler) or turn the steering wheel lock to lock (if steering cooler).

  • Perform a short test drive to bring systems to operating temperature.

  • Recheck fluid levels and inspect for leaks.

  • Confirm hoses are securely routed with no rubbing or interference.


POST-INSTALLATION CHECKLIST

✅ Fluid levels are correct (Toyota WS or PSF depending on system).

✅ No leaks at hose clamps or fittings.

✅ Hoses are routed securely, away from heat and moving parts.

✅ Front bumper is properly reinstalled.

✅ All tools and materials cleaned up and removed.


INSTALLATION COMPLETE

Your Supreme Fabworks Mishimoto Transmission/Steering Cooler Kit installation is complete.This system provides reliable cooling for your transmission or steering system under heavy loads—ideal for towing, overlanding, and rock crawling.

➡️ Mishimoto Lifetime Warranty applies to the transmission cooler. Don’t forget to register your product with Mishimoto.

PRO TIPS

  • Inspect hoses and clamps periodically—especially after the first 100 miles.

  • Carry extra Toyota WS or Power Steering Fluid in your overland toolkit.

  • Consider adding a temperature gauge to monitor transmission or steering temps.

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