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How to Bleed Kia Soul EV Coolant with LAUNCH X431 | Step-by-Step Guide

• September 04, 2026
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Learn how to properly bleed the Kia Soul EV coolant system using a LAUNCH X431 scanner. Step-by-step instructions for motor/inverter loop, troubleshooting tips, and FAQs.

Published: June 29, 2026

Quick Answer: Bleeding the Kia Soul EV Coolant System

Performing a coolant bleed on a Kia Soul EV requires a scan tool like the LAUNCH X431 to activate the electric water pump and vent air from the inverter and motor circuits. The process involves filling the reservoir, running the pump via the X431, watching for bubbles, and topping off the fluid. The entire procedure ensures no air pockets remain, preventing overheating, reduced cabin heat, and potential damage to the high-voltage battery or motor.

Why the Kia Soul EV Needs a Special Coolant Bleed

If you’ve ever bled a conventional gas engine, you know the drill: fill the radiator, run the engine, squeeze hoses, and wait for bubbles. That method won’t work on a Kia Soul EV. This electric vehicle uses two separate cooling loops, and one of them simply cannot purge air without electronic help.

The Two Separate Cooling Circuits

  • Battery Cooling Loop: Circulates coolant through the high-voltage traction battery pack. This loop can often self-bleed during normal driving, but it still benefits from a scan tool check after a replacement.
  • Motor/Inverter Loop (The Critical One): Cools the electric drive motor and the inverter that converts DC battery power to AC motor power. This circuit has a small electric water pump that only runs when the car is in "Ready" mode. During a standard gravity fill, air gets trapped at the highest point — usually inside the heater core. The result? Cold air blasting from your vents in winter.

Common Symptoms of Air in the System

  • Heater blows lukewarm or cold air (air pocket blocks coolant flow through the cabin heater core).
  • Reduced motor power or a "Check Electric Vehicle System" warning on the dash.
  • Gurgling sounds from under the dashboard or the front motor compartment.
  • Erratic coolant temperature readings on the instrument cluster.

Ignoring trapped air can lead to inverter overheating, which may trigger a costly repair. That’s why the manufacturers specifically require an active bleed using a bi-directional diagnostic tool.

What You Need: The LAUNCH X431 and Tool Preparation

You can’t just open a bleeder screw and hope for the best. To bleed the motor/inverter loop, you must command the electric water pump to run continuously. The LAUNCH X431 gives you that bi-directional control.

  • Required Tool: Any LAUNCH X431 series model (Pro, V, PAD VII, or higher) with the Kia software package and a compatible OBD2 connection. All current X431 models support this function.
  • Other Supplies: Pre-mixed Kia/Hyundai EV coolant (usually blue or pink, silicate-based), a clean funnel with a long neck, a catch pan, and nitrile gloves. Do not use standard green coolant — it will damage the seals.
  • Software Check: Before you start, update your LAUNCH X431 with the latest Kia/Hyundai software. Connect to Wi-Fi, go to the Update tab, and install the newest package. The "Coolant Air Bleeding" function lives under the Special Functions menu. If it isn’t there after updating, your specific model year may require a J2534 pass-through connection; contact LAUNCH support to verify.

Step-by-Step Bleeding Procedure

Follow this exact sequence. Skipping a step can leave air trapped, and the inverter may overheat before you realize there’s a problem.

1. Preparation: Safety and Initial Fill

  • Ensure the car is OFF and the key fob is out of range. High-voltage components are present, but the 12V auxiliary system powers the scan tool and pump.
  • Open the coolant reservoir for the motor/inverter loop. In most Soul EV models (2014–2025), this is the smaller of the two tanks, often labeled "MOTOR" or "INVERTER."
  • Fill the reservoir to the MAX line (or slightly above) with pre-mixed Kia/Hyundai EV coolant. Do not use concentrated coolant — it must be pre-diluted.

2. Connect LAUNCH X431 and Enter Special Functions

  • Plug the X431 into the OBD2 diagnostic port located under the driver’s side dashboard.
  • Turn the ignition ON by pressing the start button once. Do not press the brake pedal — you should see the dashboard lights illuminate without the "Ready" indicator.
  • Navigate through the LAUNCH X431 menu: Kia → Soul EV → select your model year (e.g., 2020+) → Special Function → Coolant Air Bleeding.

3. Activating the Electric Water Pump

  • Select the option labeled "Motor/Inverter Pump Bleed" (some versions may say "Water Pump Activation" or "Coolant Bleeding").
  • The X431 will ask you to confirm. Tap Yes to start the pump.
  • Do not start the car. The pump will run for a preset duration — typically 3 to 5 minutes.
  • Watch the return line: A small clear hose or a plastic tube returns coolant from the motor circuit back into the reservoir. You should see a steady stream of fluid flow. Watch for bubbles in that return line. Air pockets will appear as bursts of tiny bubbles.

4. Monitoring and Capping the Top Off

  • As the pump runs, the coolant level in the reservoir will drop because fluid is being pushed into the system. Keep the reservoir topped off above the "MIN" line at all times. Letting it run dry will reintroduce air.
  • If the pump stops due to the timer, and you still see bubbles, cycle the function again. Repeat until the return flow is a solid, bubble-free stream.
  • Once the flow is clear, let the pump finish its cycle, then cap the reservoir tightly.

5. Final Check and Test Drive

  • Start the car in "Ready" mode by pressing the brake and hitting the start button.
  • Turn the cabin heat to HI (high) and set the fan to LOW (1 or 2 bars).
  • Drive gently for about 5 minutes. The heater should blow hot air within the first minute. If it stays cold, air is still present — repeat the X431 bleed procedure.
  • Stop the car, let it cool for 15 minutes, then re-check the coolant level. Add fluid to the MAX line if needed.

Common Issues and Troubleshooting

Even with the LAUNCH X431, you might encounter problems. Here’s what to check.

  • Pump Does Not Run:
    • Cause: Low 12V auxiliary battery voltage. The electric water pump won’t activate if the 12V system is weak.
    • Fix: Connect a 12V battery charger or jump starter to the auxiliary battery terminals (located under the hood, usually near the fuse box). Then repeat the X431 bleed command.
  • Air Persists After 3 Cycles:
    • Cause: A leak in the system, a stuck thermostat, or a faulty water pump.
    • Fix: Inspect all hose clamps for coolant seepage. If no leaks are visible, the water pump may have a mechanical fault — this is rare but possible on high-mileage vehicles.
  • Error Code for Overheating During Procedure:
    • Cause: The inverter detected no coolant flow for an extended period.
    • Fix: Turn the ignition OFF immediately. Let the car cool for 15 minutes. Recheck the coolant level. Retry the X431 bleed function with the reservoir fully topped off.

For a deeper dive into scan tool capabilities, check out our guide on how to use LAUNCH X431 for EV diagnostics.

FAQ: Kia Soul EV Coolant Bleed

Can I bleed the coolant without a scan tool?

No, not reliably. The Kia Soul EV’s electric water pump for the motor/inverter requires a bi-directional command to run continuously. A gravity bleed or pinching hoses won’t create enough flow to dislodge air pockets. Attempting to bleed without a tool like the LAUNCH X431 almost always results in cold cabin heat and potential inverter damage.

Do I need to bleed both cooling loops?

Usually, only the motor/inverter loop needs active bleeding. The battery cooling loop often self-bleeds during normal driving as the battery heats up and coolant expands. However, if you replaced the battery coolant, you should use the X431 to run the battery pump function for a few minutes to confirm flow.

What type of coolant does a Kia Soul EV use?

Use only pre-mixed Kia/Hyundai approved EV coolant. For most Soul EV models, this is a silicate-based blue or pink fluid specifically formulated for electric vehicles. Never use standard green coolant — it contains additives that can corrode the aluminum inverter cooling passages. Check your owner’s manual for the exact specification.

My LAUNCH X431 doesn't have the "Coolant Bleed" function. What do I do?

Update the X431 software first. Connect to the internet, open the Update tab, locate the Kia software package, and install the latest version. If the function still doesn’t appear, your specific model year may not support this function through the standard menu. In that case, try using the J2534 pass-through mode with the factory Kia software, or contact LAUNCH support for guidance.

How long does the entire process take?

Plan for 30 to 45 minutes. This includes filling the reservoir, running 2–3 pump cycles (each lasting about 5 minutes), monitoring the return line for bubbles, and performing the final test drive. If you hit a snag like a weak 12V battery, add another 15 minutes for charging.

After the Service: Verifying Success

  • Heater Test: Turn the cabin heat to HI and the fan to LOW. You should feel hot air within 30 seconds. If it stays warm but not hot, the system may still have a small air pocket — consider one more bleed cycle.
  • No "Check EV System" Light: The dashboard should remain clear of any warning lamps. If a warning appears, re-scan with the X431 and clear any stored codes.
  • Stable Coolant Level: After the first full heat cycle and a cooldown period, the reservoir level should sit at the MAX line. Check it again after 24 hours and 100 miles of driving. If it drops significantly, inspect for a leak.

For more maintenance tips on electric vehicles, read our article on common Kia EV service procedures.

About the Author: Erwin Salarda is an Automotive Service Equipment Technician based in the Philippines, specializing in computerized automotive diagnostic equipment such as OBD scanners and wheel alignment systems. Since 2012, he has been actively providing technical support, equipment installation, troubleshooting, after-sales service, and hands-on training for automotive service equipment used by workshops and automotive professionals.

He has received specialized training from international suppliers and manufacturers, including Launch X431 in Shenzhen, China, Lawrence Engineering Company in Guangzhou, China, and 3Excel Wheel Alignment Company in Shenzhen, China. Through these trainings, he developed advanced expertise in automotive diagnostics, calibration, wheel alignment systems, and computerized automotive service technologies.

Erwin Salarda provides professional after-sales support and technical training for automotive diagnostic and wheel alignment equipment, helping clients maximize the performance and proper use of their tools and systems. His experience covers equipment setup, software updates, calibration procedures, troubleshooting, and operational guidance for automotive workshops and service centers.

With more than a decade of experience in the automotive equipment industry, Erwin Salarda continues to support automotive businesses by delivering reliable technical expertise and practical training solutions.

For inquiries and equipment purchases, please visit https://carlifterph.com/

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