Pressure test the low-voltage cooling system on a 2024 Model X Plaid to identify leaks in the powertrain/battery coolant loops without disturbing HV components. This is a diagnostic-only procedure performed at the coolant reservoir.

Warnings

Tools required

Parts

• Coolant reservoir cap (replace if seal damaged) × 1 — OEM Tesla Model X coolant reservoir cap

Fluids

• Tesla Battery/Motor Coolant (G-48) — top-up only if needed — 0.5 qt

Preparation

1. Park on level ground, place in P, engage parking brake.
2. Exit ALL doors with the 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 in the frunk (similar position to Model S). Remove frunk trim/cover as required, then disconnect the negative terminal first.
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 for at least 1 hour if it has been driven. Coolant under pressure when hot can cause severe burns.
7. Confirm the coolant reservoir is filled to the correct cold level before testing — a low reservoir will give a false leak indication.
8. Stage absorbent towels under the reservoir area to catch any spillage.

Procedure

1. 1

   Access the coolant reservoir
   Open the frunk and locate the powertrain coolant reservoir (translucent plastic tank with a pressure cap). Remove any plastic cowl or cover panels needed to fully access the cap. Note that the Model X may share routing with HV battery cooling — only the reservoir and its cap are to be touched.
   ⚠Do not disturb any orange-jacketed cabling or sealed HV service covers while removing trim.
2. 2

   Inspect the cap and reservoir visually
   Wipe the cap and reservoir neck clean. Inspect the cap's rubber seal for cracks, swelling, or deformation. Inspect the reservoir for stress cracks, weeping seams, and dried coolant residue (often greenish-yellow with G-48). Photograph any suspect areas before testing.
3. 3

   Slowly release residual system pressure
   With the system cool, place a shop towel over the cap and slowly rotate it to the first detent to vent any residual pressure. Once venting stops, remove the cap fully and set it aside on a clean surface.
   ⚠Even a 'cool' EV cooling system can hold residual pressure due to thermal cycling from battery management. Open slowly.
4. 4

   Verify coolant level
   Confirm the coolant is at the COLD FULL line on the reservoir. If low, top up with Tesla Battery/Motor Coolant (G-48 specification) only. Do not substitute generic coolants — Tesla's blend is specified for the aluminum and plastic components in the loop.
   ⚠Mixing non-G-48 coolant can cause precipitation and clog the battery cooling galleries, an extremely expensive failure.
5. 5

   Install the pressure tester adapter
   Select the pressure tester adapter that matches the Tesla coolant reservoir cap thread/bayonet style. Thread or lock the adapter onto the reservoir neck by hand — do not use tools that could over-stress the plastic neck. Confirm the adapter seals fully against the reservoir lip.
6. 6

   Connect the pressure pump
   Connect the hand pump to the adapter. Verify the pump's gauge reads zero. Check that the cap's stamped pressure rating is known — most automotive cooling caps are in the 1.1–1.4 bar (16–20 psi) range, but verify on the OEM cap before pumping.
   ⚠Never pressurize beyond the OEM cap's rated value. The Model X reservoir is plastic and can crack if over-pressurized.
7. 7

   Pressurize the system
   Slowly pump the tester until the gauge reaches the cap's rated pressure. Stop pumping. Do not exceed the rating. Hold the system at pressure.
8. 8

   Observe gauge for 15 minutes
   Watch the gauge. A healthy system should hold pressure with negligible drop over 15 minutes. A drop of more than ~10% in 15 minutes indicates a leak. Note: small drops as the system equalizes thermally in the first 60 seconds are normal.
9. 9

   Locate the leak (if pressure drops)
   With the system pressurized, visually inspect accessible hoses, clamps, the reservoir body, and visible coolant fittings in the frunk area for weeping or beading coolant. Use an inspection mirror and flashlight. DO NOT trace coolant lines into the HV battery pack, drive units, or anywhere near orange cables. If the leak is suspected to be at the battery pack, drive unit, octovalve, superbottle, or heat pump — STOP and refer the vehicle to a Tesla-certified technician.
   ⚠️Leaks at the HV battery thermal loop, octovalve, superbottle, or heat pump require Tesla Toolbox and HV-certified service. Do not attempt.
10. 10

    Test the cap separately
    Remove the cap from the vehicle and install it on the tester's cap adapter. Pressurize to the cap's rated value. The cap should hold within its specification; failure to hold indicates a worn seal — replace the cap with an OEM unit.
11. 11

    Release pressure and remove the tester
    Use the tester's relief valve to slowly bleed pressure to zero. Once fully depressurized, unthread the adapter from the reservoir.
    ⚠Never remove the adapter while pressure is still indicated on the gauge.

Reassembly

1. Reinstall the OEM coolant reservoir cap (or a new cap if the original failed its test). Tighten by hand to the cap's detent — do not over-torque the plastic neck.
2. Wipe down any spilled coolant. G-48 coolant is mildly corrosive to paint and should not be left on body panels.
3. Reinstall any frunk trim or cowl panels removed for access.
4. Reconnect the 12V low-voltage battery (positive first, then negative). Torque the terminal hardware to OEM specification — refer to Tesla Service Manual.
5. Close the frunk.

Verification

• Power the vehicle on and allow it to sit in Ready for 5–10 minutes. The thermal management system will cycle pumps and valves; listen for unusual gurgling (air in system) or pump noise.
• Check the touchscreen for any cooling system, battery thermal, or powertrain warnings — none should be present.
• After a short drive (10–15 minutes), park, allow to cool, and re-inspect the reservoir level and the area around the cap for any new weeping.
• If this test was performed as part of Tesla's 4-year / 50,000 mi battery coolant inspection interval, log the date and odometer reading for the next inspection.
• If any leak was found that traces toward the HV battery, drive units, or thermal manifold (octovalve/superbottle/heat pump), the vehicle requires Tesla-certified service before being driven.

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