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NormalModel 3Model Y#Cooling#Maintenance0-100 USD

Coolant bleeding: removing air after repair

≈ 3 min read
Drivetrain · RWD, AWD, AWD Performance
Updated · July 26, 2026
Contents

Quick FAQ

Why doesn't coolant circulate after cooling-system repair?
The cause is an air pocket (airlock). After any opening of the loop, the fluid sits still when you start the procedure in Service Mode, and the computer temperature climbs to 80–90 °C until the air is pushed out.
When is a vacuum coolant refill mandatory?
When the HV battery is removed and reinstalled, always: per the original Tesla manual, after that the system may only be refilled with a vacuum created (a vacuum rig on the expansion tank). Without vacuum, bleeding is acceptable only for a top-up or a minor repair, for example when the radiator was removed for cleaning.
How do I bleed air from the cooling system on a Tesla Model 3/Y?
For a minor repair: get the nose of the car up (jack or ramp) so the air rises, and run Coolant Air Purge via Service Mode; watch the temperature, shut down at 80 °C, let it cool and repeat. Usually several cycles and a top-up are needed. After battery removal this is not allowed, vacuum refill only: Coolant Fill/Drain, filling, vacuum, Coolant Air Purge and topping up to the norm.
After which jobs is coolant bleeding required?
After any work that opened the cooling loop: replacing the heat pump or its components (octovalve, supermanifold), replacing the A/C compressor, cleaning or replacing the radiator and A/C condenser, replacing the drive unit (especially LDU), and any HV-battery work where the pack coolant was drained. For battery work, vacuum refill only.
How many bleed cycles are needed?
One cycle rarely solves it, so usually several are needed: start the procedure, wait for 80 °C, shut down, let it cool, repeat. Between cycles and at the end you must top the coolant back to the proper level.
Can I bleed coolant without Service Mode?
There's no factory procedure outside Service Mode on Tesla Model 3/Y: the system is designed to run the bleed routine specifically from Service Mode. Without it, a normal refill through the expansion tank will hit the airlock and fail.

Description

After coolant system repair the coolant doesn't circulate: the fluid sits still when the procedure is started in Service Mode. The computer temperature climbs to 80-90°C. The cause is an air pocket.

Solution: two scenarios

The main rule (per the original Tesla manual): after removing and installing the HV battery the system may only be refilled with a vacuum created. Without vacuum, bleeding is acceptable only for a top-up or a minor repair, for example when the radiator was removed for cleaning.

Scenario 1: minor repair / top-up (no vacuum)

  1. The nose of the car must be raised (jack or ramp) so the air goes up and out.
  2. Run the air bleed procedure (Coolant Air Purge) via Service Mode.
  3. Watch the temperature, stop at 80°C, let it cool, repeat.
  4. Several bleeding cycles may be required.
  5. Top up coolant after the procedure.

Scenario 2: after HV battery removal, vacuum refill only

The procedure per the Tesla manual:

  1. In Service Mode start the Coolant Fill/Drain mode (in Toolbox it is the procedure PROC_VCFRONT_X_THERMAL-FILL-DRAIN). The drive rails must be off, otherwise the procedure will stop.
  2. Remove the coolant reservoir cap and fill the system: on cars with a heat pump, to the MAX line; on cars without a heat pump (superbottle), roughly 6 mm above MAX.
  3. Create a vacuum with the vacuum rig on the bottle: the vacuum pulls the coolant into the empty loops and leaves no air pockets.
  4. Run Coolant Air Purge: in Service Mode, Thermal → Coolant System → Coolant Purge Start (in Service Mode Plus, via Drive Unit / Drive Inverter Replacement → Coolant Air Purge; in Toolbox, TEST_VCFRONT_X_THERMAL-COOLANT-AIR-PURGE).
  5. The procedure runs for about 10 minutes, and the pumps vary their speed between 3,500–6,500 RPM (visible on the PT Thermal tab). While it is running, keep the level between NOM and MAX, topping up as the fluid moves into the loops.
  6. If the speed hovers around 7,000 RPM, air remains, so repeat the procedure.
  7. After it finishes, top up to the norm: with a heat pump, to MAX; without one, ~6 mm above MAX. Close the reservoir cap.

The vacuum rig: gauge (cmHg/bar), ball valve and hose fitting

The rig screwed onto the coolant bottle in place of the cap

Vacuum pulls coolant into the system from the canister through the hose

Community experience TESLA Belarus

From the TESLA owner's group BELARUS chat, analysis of 400 000 messages.

Who reported the issue: Ruslan

Who found the fix: Pasha n1claus, Denis

Discussion in Telegram: #129269

When bleeding is most often needed

Coolant bleeding with air removal is usually required after any work where the system was opened:

  • Replacing the heat pump or its components (octovalve, supermanifold). On Model Y the heat pump with the octovalve has been fitted since launch (2020), on Model 3 since the 2021 model-year refresh (2021 heat pump issues).
  • Replacing the A/C compressor or refrigerant lines (Model 3/Y AC compressor failure).
  • Cleaning / replacing the radiator and A/C condenser: coolant usually spills during disassembly (radiator and condenser cleaning).
  • Replacing the drive unit, especially the LDU (Large Drive Unit), which shares the cooling loop with the battery (LDU problems S/X).
  • Any HV-battery work where the pack coolant was drained: here vacuum refill ONLY (scenario 2).

In all these cases a standard refill via Service Mode will hit the airlock unless the procedure above is performed.

Reviewed for accuracy by tsk.by · 26 July 2026
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