Mechanic Wiki: How to Perform Coolant Bleed on Hyundai Ioniq 5 EV with LAUNCH X431

Learn how to bleed coolant on a Hyundai Ioniq 5 EV using a LAUNCH X431. Step-by-step guide with troubleshooting tips for proper battery thermal management.

Published: June 27, 2026

Quick Answer

To perform a coolant bleed on a Hyundai Ioniq 5 EV using a LAUNCH X431, you must enable the electric water pump via the diagnostic tool’s “Special Function” menu. The process involves filling the reservoir to the MAX line, running the electronic bleed cycle (10–15 minutes), monitoring the coolant level as air is purged, and topping off as needed. This procedure is mandatory after any coolant system service because trapped air can cause overheating and battery thermal management failures.

When to Perform a Coolant Bleed on an Ioniq 5

Performing a coolant bleed on the Ioniq 5 isn’t a routine maintenance item—it’s a targeted service step. You’ll need to run this procedure in the following scenarios:

After Coolant Replacement: Whenever you drain and refill the high-voltage battery coolant loop, air inevitably enters the system. The bleed cycle forces those pockets out.
After Component Repair: If you’ve replaced the electric water pump, heater, chiller, or any high-voltage cooling hoses, bleeding is essential.
Low Coolant Warning: If the low coolant warning illuminates after a top-off, it often means an air lock is preventing proper circulation. The X431 will help break that lock.
Overheating or Reduced Performance: Symptoms such as rapid battery temperature rise during fast charging or noticeably slower DC charging speeds can indicate trapped air. The coolant bleed procedure restores proper thermal management.

In my experience, many Ioniq 5 owners skip this step after a DIY coolant change and then wonder why their battery temperature spikes. The tool makes all the difference.

Tools and Prerequisites

Before you dive in, gather the right equipment and set up the vehicle properly.

Item	Specification/Requirement
Diagnostic Tool	LAUNCH X431 (any model with Hyundai EV software and “Special Function” access)
Coolant	OEM-approved EV coolant (Hyundai part number 07100-00410 or equivalent)
Safety Gear	Insulated gloves (HV safety rated), safety glasses
Vehicle State	Park, ignition in READY mode (green car icon), parking brake engaged
12V Battery	Must be fully charged; use a battery maintainer if below 12.4V

Critical note: The Ioniq 5’s cooling pump is electric and only runs when commanded by the diagnostic tool. Without the LAUNCH X431 (or a similarly capable scanner), you cannot properly bleed the system. As we covered in our guide on [link to related guide on EV cooling system basics], traditional gravity bleeding won’t work here.

Step-by-Step Coolant Bleed Procedure

Step 1: Prepare the Vehicle and Connect the Tool

Set the Ioniq 5 to READY mode by pressing the brake pedal and tapping the start button. Confirm the green car icon is lit on the dashboard.
Locate the OBD-II port under the driver’s side dashboard. Connect the LAUNCH X431 cable or Bluetooth adapter.
Launch the diagnostic software: select Hyundai > IONIQ 5 (NE) . Then run System Scan to identify all control modules. This takes about 30 seconds.

Step 2: Open the Expansion Tank and Check Coolant

While the tool scans, open the hood and find the coolant expansion tank (translucent plastic, located near the front of the engine bay on the driver’s side). Verify the coolant level is at or near the MAX line. If it’s low, top it off now—you don’t want to run the pump dry.

Step 3: Access the Coolant Air Bleeding Function

On the X431, navigate to Special Function or Service & Maintenance from the main menu.
Scroll down to Coolant Air Bleeding or Water Pump Activation. In some software versions, you’ll find it under Battery Management System (BMS) > Special Function.
Select the function. The tool will display an on-screen warning: “Ensure coolant level is at MAX.” Confirm.

If your X431 doesn’t show this exact label, check for “Water Pump Actuation Test” under the BMS menu. It will work the same way—just run it for 10–15 minutes.

Step 4: Initiate the Air Bleed Cycle

Press Start or Execute. The X431 sends a command to run the electric coolant pump continuously.
The tool displays a countdown timer—typically 600 seconds (10 minutes) .
Observe the expansion tank. You’ll see coolant begin to circulate back into the tank. This is the pump pushing fluid through the system.
Listen for air. You’ll likely hear gurgling or bubbling sounds as air pockets escape. That’s normal.

Step 5: Monitor and Refill During the Cycle

As air is purged, the coolant level in the reservoir will drop. Keep an eye on it.
Refill gradually to the MAX line using your approved EV coolant. Do not overfill—the system needs headspace for expansion.
Continue monitoring until the 10-minute cycle completes. The pump will automatically stop when the timer reaches zero.

Step 6: Post-Bleed Check and Final Steps

Check for flow. After the cycle ends, look for a steady stream of coolant returning into the expansion tank. A trickle or no movement means air is still trapped.
If flow is weak, run the cycle a second time. Sometimes a single pass isn’t enough, especially after a full coolant drain.
Top off to the MAX line one final time.
Road test. Drive the Ioniq 5 for 10–15 minutes, monitoring the battery temperature gauge on the instrument cluster. Recheck the coolant level the next morning (cold check) and add if necessary.

I’ve found that a second cycle nearly always eliminates persistent gurgling sounds. Don’t rush this part.

Troubleshooting Common Issues

Issue 1: Pump Does Not Run / Tool Error

Cause: The wrong control module was selected, or the 12V battery voltage is too low. The electric pump needs at least 12.4V to operate.
Fix: Ensure the vehicle is in READY mode (green car icon). Connect a 12V battery charger if the voltage is low. If using a generic LAUNCH X431, update the software to the latest IONIQ 5 definition (2024/2025 release). The “Water Pump Actuation Test” under BMS is a reliable fallback.

Issue 2: Coolant Level Drops Rapidly During Bleed

Cause: A large air pocket is being purged, or there’s a system leak.
Fix: Stop the cycle immediately. Check all hose clamps and the water pump area for drips. If no leak is visible, refill to MAX and restart. If the level drops again without a leak, inspect the cabin heater core (often hidden behind the dashboard). In rare cases, a heater core leak dumps coolant inside the vehicle.

Issue 3: Gurgling Sound After Bleed

Cause: The cycle duration wasn’t long enough to purge all trapped air.
Fix: Run the coolant air bleeding function a second time. Afterward, turn the HVAC to HI and fan speed to max for 5 minutes. This pushes remaining air through the heater core and out of the system.

Important Safety Precautions

High Voltage: The Ioniq 5 operates on an 800V battery architecture. The cooling loop contains high-voltage components (heater, chiller). Do not perform this service without proper HV safety training. When in doubt, consult a certified EV technician.
Hot Coolant: If the vehicle was driven recently, the coolant can exceed 150°F (65°C). Allow the system to cool for at least one hour before opening the reservoir. Burns are a real risk.
Coolant Type Matters: Use only OEM-approved EV coolant (Hyundai 07100-00410 or equivalent). Mixing generic coolant with the special fluid can damage the battery’s thermal insulation and void your warranty. For more details, check out our article on [link to related guide on EV coolant types and compatibility].
12V Battery Care: The electric pump draws significant current. If your 12V battery is weak, charge it before starting the procedure. A low battery can interrupt the cycle mid-way.

FAQ

How long does the LAUNCH X431 coolant bleed process take?

The tool runs a 10-minute automatic cycle. Including prep, refilling, and a second cycle if needed, the entire procedure takes about 20–30 minutes.

Can I bleed the Ioniq 5 coolant without a LAUNCH X431?

No. Unlike traditional cars, the Ioniq 5 has an electric water pump that requires a diagnostic command to run continuously. A scan tool with “Special Function” capability is mandatory. The LAUNCH X431 is one of the most commonly used tools for this job.

Will driving the car help remove air pockets?

Partially. Driving can shift small pockets, but without forcing the pump to run at a constant speed (as the X431 does), large air pockets may remain stagnant. Always use the tool first, then drive as a final verification step.

Do I need to lift the vehicle to bleed the system?

No. The Ioniq 5’s electronic bleed procedure is designed to be done with the vehicle on level ground in READY mode. Lifting is not required—the coolant reservoir and OBD-II port are both easily accessible from ground level.

What if my LAUNCH X431 doesn’t have the “Coolant Bleed” option?

Update your software to the latest 2024/2025 version. If the option remains missing, use the Water Pump Actuation Test under the Battery Management System (BMS) menu. Run it for 10–15 minutes, monitoring the expansion tank for flow. This works identically to the dedicated bleed function.

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/