Pressure test the low-voltage cooling system on a 2024 Model Y Performance to identify leaks in coolant hoses, fittings, or the expansion tank. This is a non-invasive diagnostic — do not open or disturb the HV battery thermal loop, octovalve, or heat pump assemblies.

Warnings

Tools required

Parts

• Replacement expansion tank cap (if existing cap fails pressure hold) × 1 — OEM Tesla coolant reservoir cap

Fluids

• Tesla Battery/Motor Coolant (G-48) — top-up only if level drops — 1 qt

Preparation

1. Park on level ground, place in P, engage parking brake.
2. Exit ALL doors with key fob away from the vehicle. Wait at least 2 minutes for HV systems to fully de-energize, even on this non-HV job.
3. Disconnect the 12V low-voltage battery (located behind/under the rear seat or in the front trunk area depending on 2024 build — verify location before cutting power). Follow Tesla's documented LV disconnect sequence.
4. DO NOT touch, cut, or pierce ANY orange cable — these are high-voltage and lethal.
5. If at any point you encounter an orange cable, an HV component, or are unsure if a system is de-energized: STOP and consult a Tesla-certified technician.
6. Allow the vehicle to cool fully (minimum 2 hours after driving or any preconditioning cycle). The cooling system is shared with the HV battery loop and may remain warm even when ambient cabin is cool.
7. Open the frunk and locate the coolant expansion/reservoir tank. Confirm coolant level is between MIN and MAX before testing.
8. Place absorbent shop towels under the reservoir to catch any seepage during cap removal.

Procedure

1. 1

   Visual inspection of the cooling system
   With the frunk open, visually inspect all visible coolant hoses, clamps, the expansion tank, and the area around the radiator pack for staining, weeping, or dried coolant residue (G-48 leaves a pinkish/clear residue). Use a flashlight and mirror. Do NOT remove any covers that expose orange HV cabling.
2. 2

   Verify cool, depressurized system
   Confirm the system is cool to the touch. Slowly rotate the expansion tank cap a quarter turn to release any residual pressure before fully removing. Listen for a hiss; if the system holds pressure even when cold, that itself is abnormal — note it.
   ⚠Even on a 'cold' Tesla, the HV battery thermal loop can hold residual pressure if a recent charge or preconditioning cycle occurred.
3. 3

   Remove the expansion tank cap
   Fully remove the OEM coolant reservoir cap. Inspect the cap seal and pressure-relief spring for cracks, deformation, or coolant crust. Set the cap aside on a clean towel — you will pressure-test it separately.
4. 4

   Install the pressure tester adapter
   Select the adapter from your universal kit that matches the Tesla expansion tank neck. Thread or lock the adapter onto the reservoir hand-tight, ensuring the seal is fully seated. Do not use tools to over-tighten — the reservoir is plastic.
   ⚠Cross-threading or over-torquing the adapter will crack the plastic neck of the reservoir. This is a non-serviceable assembly on Model Y.
5. 5

   Connect the pressure pump and pressurize
   Connect the hand pump to the adapter. Slowly pump pressure up to the rated value printed on the OEM cap (do not exceed). Pump in small increments and observe the gauge between strokes.
   ⚠️Do not exceed the cap's rated pressure. Over-pressurization can damage the octovalve, heat pump, or HV battery cold plate seals — repairs that are dealer-only.
6. 6

   Hold and observe
   Hold the system at test pressure for a minimum of 10–15 minutes. Watch the gauge. A healthy system should hold steady with minimal drop. A slow drop indicates a leak; a rapid drop indicates a significant failure point.
7. 7

   Locate the leak (if pressure drops)
   While the system is pressurized, inspect all accessible hose connections, the reservoir body, the radiator inlet/outlet, and visible coolant lines for active weeping. Use a flashlight and mirror. DO NOT probe or disturb any line that runs to or from the octovalve, heat pump, or HV battery — note the location of the leak and stop.
   ⚠️If the leak originates at the octovalve, superbottle, heat pump, or any line entering the HV battery pack — STOP. This requires Tesla-certified service.
8. 8

   Release pressure
   Slowly release pressure using the tester's bleed valve. Do NOT simply unscrew the adapter under pressure. Once the gauge reads zero, remove the adapter from the reservoir.
9. 9

   Pressure-test the cap separately
   Using the cap adapter from the test kit, pressurize the OEM reservoir cap to its rated value. The cap should hold pressure and release at its rated relief point. Replace the cap if it fails to hold or fails to relieve correctly.
10. 10

    Document findings
    Record the starting pressure, ending pressure, hold time, and any observed leak locations. If no leak found and pressure held, the low-voltage portion of the cooling system is sound. If a leak is found in a non-HV-adjacent location, plan the appropriate repair. If HV-adjacent, refer to a Tesla service center.

Reassembly

1. Reinstall the OEM (or new) expansion tank cap hand-tight until it clicks/seats fully.
2. Verify coolant level is at the proper cold-fill mark; top up only with Tesla Battery/Motor Coolant (G-48) if needed. Do NOT mix coolant types — Tesla's G-48 is specific.
3. Wipe down the reservoir and surrounding area to remove any spilled coolant (G-48 is conductive when wet and can damage electrical connectors).
4. Reconnect the 12V low-voltage battery following Tesla's documented sequence.
5. Close the frunk. Allow the vehicle to wake fully and verify no coolant or thermal warnings appear on the center display.

Verification

• Power up the vehicle and check the touchscreen Service menu for any active coolant, thermal, or battery temperature alerts.
• Allow the HV battery thermal management system to cycle (a short drive or a charging session will trigger it). After cycling, recheck the coolant reservoir level — it should remain stable.
• Re-inspect the reservoir and previously suspect areas after 24 hours for any new weeping or staining.
• Log this pressure test against Tesla's recommended 4-year / 50,000-mile coolant system inspection interval — note the date and odometer reading for the next service.
• If any leak was identified at an HV-adjacent component (octovalve, heat pump, superbottle, battery cold plate lines), the vehicle must go to a Tesla service center — these are not DIY-serviceable.

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