Pressure test the cooling system on a 2012 Tesla Roadster to identify leaks in the powertrain/PEM cooling loop. The Roadster uses a conventional low-voltage cooling circuit with a coolant expansion tank, accessible without disturbing HV components.

Warnings

Tools required

Parts

• Replacement expansion tank cap (only if cap fails its pressure test) × 1 — OEM-specification Roadster coolant reservoir cap

Fluids

• Tesla Battery/Motor Coolant (G-48) — top-up only if level is low after test — 1 qt

Preparation

1. Park on level ground, place in P (or in gear with manual-equipped early Roadsters), 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 before working in any area near HV components. On the Roadster, the 12V battery is located in the front compartment — refer to the owner's manual for exact location.
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 sit for at least 1 hour after any driving so coolant temperature and pressure normalize.
7. Open the rear clamshell / engine cover per the manufacturer-specified procedure to access the coolant expansion tank.
8. Visually inspect the coolant level in the expansion tank — it should be between MIN and MAX. Top up with Tesla Battery/Motor Coolant (G-48) only if low.
9. Lay clean rags around the expansion tank to catch any residual coolant when removing the cap.

Procedure

1. 1

   Visual inspection of cooling system
   Before pressure testing, visually inspect all accessible coolant hoses, clamps, the expansion tank, radiator (front of vehicle), and the PEM/motor coolant fittings for signs of leaks, staining, crusty residue, or weeping. Note any suspect areas to re-check during the pressure test.
   ⚠Do not move or tug on orange HV cabling while inspecting near the rear PEM and motor area.
2. 2

   Confirm system is cool
   Carefully touch the upper coolant hose and the expansion tank — they must be at ambient temperature. If warm, wait longer. Slowly rotate the expansion tank cap to its first detent to vent any residual pressure before fully removing.
   ⚠️Hot coolant under pressure can spray and cause serious burns. When in doubt, wait longer.
3. 3

   Remove the expansion tank cap
   Once depressurized, fully remove the coolant expansion tank cap. Set it on a clean rag — you will pressure-test the cap separately.
4. 4

   Install the pressure tester adapter
   Select the pressure tester adapter that matches the Roadster's expansion tank filler neck. Thread or seat it onto the filler neck per the tester manufacturer's instructions, ensuring the gasket is fully seated and square. Do not cross-thread.
5. 5

   Connect pressure tester pump
   Connect the hand pump to the adapter. Confirm the gauge reads zero before pressurizing.
6. 6

   Pressurize the system
   Slowly pump the tester up to the system's rated cap pressure — do not exceed the pressure stamped on the OEM cap. Stop pumping as soon as the rated pressure is reached.
   ⚠Exceeding rated pressure can rupture hoses or the plastic expansion tank. Roadster cooling components are not easily sourced.
7. 7

   Hold and observe pressure
   Hold the pressure for a minimum of 15 minutes. Watch the gauge: a healthy system should hold pressure with little to no drop. A steady decline indicates a leak. While holding pressure, walk around the vehicle and inspect: front radiator, all hose connections, the expansion tank seams, the coolant pump area, and the PEM/motor coolant fittings (without contacting orange cabling).
8. 8

   Locate any leaks
   If pressure drops, look for visible coolant weeping, dripping, or a wet/glossy area. Common Roadster leak points include hose clamps at the front radiator, the expansion tank itself, and connections at the rear powertrain cooling loop. Document all findings before depressurizing.
9. 9

   Release pressure and remove tester
   Use the tester's relief valve to slowly bleed pressure to zero. Confirm the gauge reads zero, then remove the adapter from the filler neck. Wipe the neck and surrounding area with a clean rag.
10. 10

    Pressure test the cap separately
    Install the cap onto the tester's cap-test adapter. Pump up to the cap's rated pressure. The cap should hold pressure briefly then release at its rated value. A cap that won't hold pressure or releases too early must be replaced with a manufacturer-specified equivalent.

Reassembly

1. Confirm coolant level is at MAX cold line; top up with Tesla Battery/Motor Coolant (G-48) only if needed.
2. Reinstall the expansion tank cap (or new replacement cap) and tighten until it clicks/seats per its design.
3. Wipe down the expansion tank and surrounding area so any future leaks are easy to spot.
4. Close the rear clamshell / engine cover per the manufacturer-specified procedure.
5. Reconnect the 12V low-voltage battery.

Verification

• Start the vehicle and bring the cooling system up to normal operating temperature. Monitor for any coolant temperature warnings on the instrument cluster (VDS).
• After a short drive, allow the vehicle to cool, then re-inspect the expansion tank cap area, all hoses, and the radiator for any new weeping.
• Recheck coolant level after the first heat cycle — if it has dropped, there is still a leak that must be diagnosed.
• Per Tesla's current guidance, battery/motor coolant should be inspected every 4 years or 50,000 miles. Note today's mileage and date so the next inspection can be scheduled.
• If any leak was identified during the test, do not return the vehicle to service until repaired — coolant loss on the Roadster can lead to PEM/motor overheating.

More procedures for this vehicle