Pressure test of the low-voltage cooling system on a 2024 Cybertruck Cyberbeast to identify external leaks. This procedure covers the accessible coolant circuit only — it does NOT involve the HV battery thermal loop, octovalve, or heat pump assemblies.

Warnings

Tools required

Parts

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

Fluids

• Tesla Battery/Motor Coolant (G-48) — top-up only if level drops during test — 1 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 low-voltage battery (Cybertruck uses a 48V LV architecture — verify the correct disconnect procedure for the 48V system before touching any connector).
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 cooling system to cool fully — confirm reservoir is cool to the touch before removing any cap.
7. Open the frunk and locate the accessible coolant expansion reservoir for the powertrain/auxiliary loop. Confirm it is NOT the HV battery thermal loop reservoir before proceeding.
8. Place absorbent pads beneath the reservoir to catch incidental drips.
9. Inspect visible coolant hoses, quick-connects, radiator end tanks, and the front cooling module for obvious staining, dye residue, or weeping prior to pressurizing.

Procedure

1. 1

   Verify which coolant loop you are testing
   The Cybertruck has multiple thermal loops. Visually trace the reservoir lines from the cap downward. Confirm the reservoir is part of the accessible powertrain/auxiliary loop and is NOT routed into the HV battery, octovalve, or heat pump manifold. If routing is unclear, stop and reference Tesla service documentation. Do not pressurize the HV battery loop under any circumstances.
   ⚠️Pressurizing the HV battery thermal loop can damage cells and is outside the scope of this procedure.
2. 2

   Check and record baseline coolant level
   Note the current coolant level in the expansion reservoir relative to the MIN/MAX markings. Photograph if possible. This baseline allows you to detect if fluid drops during the pressure hold.
3. 3

   Remove the expansion tank cap
   With the system fully cold, slowly rotate the cap to vent any residual pressure, then remove. Inspect the cap seal and pressure relief valve for cracking, swelling, or contamination. Set the cap aside on a clean surface.
   ⚠Even a 'cold' system can hold residual pressure if recently driven. Vent slowly.
4. 4

   Pressure test the cap separately
   Install the cap onto the pressure tester's cap adapter. Pump up to the cap's rated pressure (printed on the cap or per OEM specification). The cap should hold its rated pressure without bleeding off, and should release cleanly above its rated value. Replace the cap if it fails to hold or fails to relieve at spec.
5. 5

   Install pressure tester onto reservoir
   Select the correct adapter for the Cybertruck reservoir neck. Thread/seat the adapter snugly per the tester manufacturer's instructions — do not cross-thread. Connect the pressure pump to the adapter.
   ⚠A poor adapter seal will mimic a system leak. Verify the adapter itself holds pressure on a known-good fitting if results are inconsistent.
6. 6

   Pressurize the system to specification
   Slowly pump the tester up to the system's rated cap pressure — do not exceed it. Watch the gauge as you pump; if pressure will not build at all, you have a major leak (open hose, failed quick-connect, or cracked tank).
   ⚠Stop immediately if you hear hissing from inside the cabin HVAC area or under the battery — this could indicate a leak into a sensitive area. Depressurize and investigate.
7. 7

   Hold and observe for 15 minutes
   Allow the system to sit pressurized. A healthy system should hold within roughly 10% of test pressure over 15 minutes. While holding, inspect: front cooling module and radiator seams, all visible quick-connect collars, hose-to-pump junctions on accessible (non-HV) coolant pumps, the reservoir itself (especially around the seam and level sensor), and the underside of the front subframe area for drips.
8. 8

   Localize any leak
   If pressure drops, use a flashlight and inspection mirror to find the source. For slow leaks, UV dye added to the reservoir prior to testing will reveal weep points under UV light. Do NOT trace lines into the HV battery thermal pack — if the leak source disappears into HV-loop plumbing, stop and refer to a Tesla-certified technician.
   ⚠️If a leak appears to originate from the HV battery, octovalve, superbottle, or heat pump assembly, STOP. This is outside the scope of this procedure.
9. 9

   Release pressure safely
   Use the tester's bleed valve to slowly release system pressure. Do not crack the adapter loose under pressure. Once the gauge reads zero, remove the adapter from the reservoir.
10. 10

    Reinstall the cap and top off if needed
    If coolant level dropped during testing, top off with Tesla-spec G-48 battery/motor coolant to the correct cold-fill mark. Reinstall the expansion tank cap (or a new cap if the original failed step 4) and seat fully until it clicks/locks per its design.
    ⚠Do not substitute non-G-48 coolant. Mixing chemistries can cause sludge and corrosion in aluminum components.

Reassembly

1. Confirm the expansion tank cap is fully seated and locked.
2. Remove absorbent pads and clean any spilled coolant from surrounding components — coolant residue on stainless will streak.
3. Reinstall any access covers removed for inspection. Torque to OEM specification — refer to Tesla Service Manual for any covers or brackets disturbed.
4. Reconnect the 48V low-voltage battery following the correct Cybertruck reconnection sequence.
5. Close the frunk.

Verification

• With the LV system reconnected, power the vehicle on (do not necessarily need to drive). Check the touchscreen for any thermal system, coolant level, or pump-related alerts.
• Allow the vehicle to run through a normal thermal cycle (if safe to do so) and recheck the reservoir level after the system has cooled — level should be stable at the cold-fill mark.
• Recheck visually for any new weep points after the first heat cycle, as some leaks only appear under thermal expansion.
• Note: Tesla now recommends battery/motor coolant inspection at 4 years / 50,000 miles. Log this pressure test date so the next inspection interval can be tracked.
• If the system failed to hold pressure and the source could not be safely identified outside HV components, do not return the vehicle to service — refer to a Tesla-certified technician.

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