Coolant bleeding — removing air after repair

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.

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.

Links

• Cooling System Refill and Bleed (Tesla Service Manual): https://service.tesla.com/docs/ModelS/ServiceManual/Palladium/en-us/GUID-A474F6DC-B48D-4184-8B5F-A4A4FB8ED1FA.html
• Cooling System Bleed (Model 3 Service Manual): https://service.tesla.com/docs/Model3/ServiceManual/2024/en-us/GUID-16455A85-902B-4E9A-84FE-F6EF7BC0D0FB.html