Coolant Temperature Sensor

Procedure to replace the coolant temperature sensor on a 2009 Aston Martin DB9 6.0L V12, including coolant partial drain, sensor access, removal, installation, and system refill with air purge.

Warnings

Tools required

Parts

• Coolant temperature sensor × 1 — Use OEM Aston Martin specification
• Coolant temperature sensor O-ring or seal × 1 — Usually included with sensor

Fluids

• OAT 50/50 coolant — 2 qt

Preparation

1. Ensure engine is completely cold to the touch (minimum 2 hours after last operation).
2. Park vehicle on level surface and engage parking brake.
3. Disconnect negative battery terminal to prevent fault codes during sensor disconnection.
4. Remove engine cover by pulling upward on the retaining points (press-fit attachment).
5. Place drain pan beneath radiator drain location.

Procedure

1. 1

   Partially drain cooling system
   Locate the cooling system drain point at the bottom of the radiator (petcock or lower hose connection — verify exact location against Aston Martin service documentation for this chassis). Drain coolant until the level drops below the coolant temperature sensor location (expect 1-2 gallons to drain). If no petcock is fitted, drain via the lower radiator hose into a suitable pan. Monitor the coolant stream and close the petcock once the level is sufficiently below the sensor mounting point. This minimizes coolant loss while providing safe sensor removal access. Note: Locate the cooling system drain point at the bottom of the radiator or the lower radiator hose connection. If a drain petcock is present, open it by turning counterclockwise; otherwise partially drain by carefully loosening the lower radiator hose. Drain coolant until the level drops below the coolant temperature sensor location (typically 1-2 gallons will drain). Note: Locate the cooling system drain point at the bottom of the radiator (petcock if equipped, otherwise the lower radiator hose connection). If a petcock is present, open it by turning counterclockwise; otherwise partially drain by loosening the lower hose. Drain coolant until the level drops below the coolant temperature sensor location (verify actual drain volume against OEM documentation). Monitor the coolant stream and close/reseal the drain once the level is sufficiently below the sensor mounting point. This minimizes coolant loss while providing safe sensor removal access.
   Torque spec

   Drain Petcock9 Nm (7 lb-ft)
2. 2

   Locate coolant temperature sensor
   The coolant temperature sensor is typically mounted on the right cylinder bank (passenger side) engine block or thermostat housing. On the 6.0L V12, it is typically located on a coolant passage near the right bank — verify against OEM documentation whether it mounts to the thermostat housing, coolant crossover pipe, or cylinder head passage. Use a work light to identify a two-wire connector attached to a brass or plastic sensor body threaded into the coolant passage. The sensor will have a hexagonal or wrench-flat section for removal. Note: On the 6.0L V12, the sensor location varies — verify against Aston Martin service documentation, as it may be on the thermostat housing, a coolant crossover/outlet pipe, or a cylinder head coolant passage near the right bank. Note: On the 6.0L V12, it is typically located on the right bank near a main coolant passage (thermostat housing, coolant crossover, or cylinder head)—verify the exact location against OEM documentation for this vehicle.
   ℹ️If sensor location differs from description, trace the engine coolant temperature sensor wiring harness from the ECU connector bundle. The sensor will be along a main coolant passage with direct coolant flow exposure.
3. 3

   Disconnect sensor electrical connector
   Press the locking tab on the sensor electrical connector and carefully pull the connector straight off the sensor. Wiggle gently if resistance is felt, but do not force. Inspect the connector terminals for corrosion or damage. If connector is corroded, clean terminals with electrical contact cleaner before proceeding.
4. 4

   Remove coolant temperature sensor
   Using an appropriate wrench or deep socket, carefully unthread the coolant temperature sensor from its mounting location. Turn counterclockwise to remove. Expect residual coolant to drain from the sensor bore once removed (have shop towels ready). Remove the sensor completely and inspect the threads and sealing surface for debris or damage.
5. 5

   Inspect sensor bore and prepare new sensor
   Clean the sensor mounting threads in the engine block or housing using a clean lint-free shop towel. Remove any old sealant, corrosion, or debris. Inspect threads for damage. Verify the new coolant temperature sensor includes a new O-ring or sealing washer. If a separate seal is provided, install it onto the new sensor according to the manufacturer's instructions. Do not reuse the old seal.
6. 6

   Install new coolant temperature sensor
   Thread the new coolant temperature sensor into the mounting bore by hand, turning clockwise. Ensure the sensor threads engage smoothly without cross-threading. Hand-tighten the sensor until it seats against the sealing surface. Then tighten to the proper torque specification using a torque wrench. Torque the sensor to the Aston Martin OEM specification — do not rely on a generic value, as coolant temperature sensors vary widely and overtightening can crack the body or damage threads. If the OEM figure is unavailable, consult factory documentation before final tightening. Note: Torque the sensor to the OEM-specified value for the 2009 DB9 6.0L V12 (verify against Aston Martin service documentation before final tightening); do not apply an unverified generic torque to an aluminum coolant passage. Note: Torque the sensor to the OEM specification for this vehicle (not confirmed here—do not guess). If OEM torque is unavailable, hand-seat the sensor and apply only enough additional turn to compress the seal without over-torquing the aluminum threads.
   ⚠Over-tightening the sensor can crack the sensor body or damage the threads in the aluminum block. Use a torque wrench and do not exceed specified torque.
7. 7

   Reconnect sensor electrical connector
   Push the electrical connector firmly onto the new sensor until the locking tab clicks into place. Gently tug on the connector to verify it is securely latched. Ensure the wiring is routed clear of hot exhaust components and moving parts.
8. 8

   Close drain petcock and refill coolant
   Close the radiator drain point securely (hand-tighten the petcock, or reconnect and clamp the lower hose if no petcock is fitted). Do not overtighten. Slowly refill the cooling system with the Aston Martin specified 50/50 coolant (verify required chemistry against OEM documentation) through the expansion tank or radiator filler neck. Fill until coolant reaches the cold fill line on the expansion tank. Add coolant slowly to allow air to escape from the system. Note: Slowly refill the cooling system with the Aston Martin OEM-specified coolant (correct type and 50/50 dilution) through the expansion tank or radiator filler neck, having enough volume on hand to replace the 1-2 gallons drained. Note: Slowly refill the cooling system with the OEM-specified Aston Martin coolant (verify exact specification and concentration against factory documentation) through the expansion tank or radiator filler neck.
9. 9

   Bleed air from cooling system
   If the vehicle is equipped with a cooling system bleed screw (located at the highest point of the system per OEM documentation), use it for bleeding; otherwise follow the Aston Martin fill-and-bleed procedure using the expansion tank. Loosen the bleed screw 1-2 turns while continuing to add coolant to the expansion tank. When a steady stream of coolant (not air bubbles) flows from the bleed screw, close it to the specified torque. Top off the expansion tank to the cold fill line. Start the engine and allow it to warm to operating temperature with the expansion tank cap loosely installed. Monitor coolant level and add as needed while the engine purges remaining air. Once the thermostat opens and coolant circulates fully, the level will stabilize. Note: If the system is equipped with a bleed screw, locate it at the highest point of the cooling system (commonly near the thermostat housing)—verify presence and location against OEM documentation, as some systems self-bleed through the expansion tank.
   ⚠Monitor engine temperature gauge during the bleeding process. If temperature rises above normal operating range, shut off the engine immediately and allow to cool. This may indicate insufficient coolant or trapped air.
   Torque spec

   Bleed Screw9 Nm (7 lb-ft)
10. 10

    Final system check and secure expansion tank cap
    With the engine at operating temperature, check for leaks around the new coolant temperature sensor and all cooling system connections. Shut off the engine and allow it to cool for 10-15 minutes. Recheck the coolant level in the expansion tank and top off to the hot fill line if needed. Securely install the expansion tank cap. Reconnect the negative battery terminal. Reinstall the engine cover by aligning the press-fit mounting points and pressing down firmly until seated.

Reassembly

1. Torque all fasteners to specifications using a calibrated torque wrench.
2. Ensure all electrical connectors are fully seated with locking tabs engaged.
3. Verify coolant level is at the appropriate cold or hot fill line after final cool-down.
4. Double-check that no tools or shop towels were left in the engine bay.

Verification

• Start the engine and verify that the coolant temperature gauge reads normally and climbs smoothly to operating temperature.
• Use a diagnostic scan tool to verify the engine coolant temperature sensor is reporting realistic values to the ECU (typically 180-220°F at full operating temperature).
• Check for any coolant leaks around the sensor installation point with the engine at operating temperature.
• Verify no warning lights or fault codes related to coolant temperature are present in the instrument cluster.
• After a short test drive, recheck coolant level in the expansion tank when cold and top off if necessary.

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

Chasing one of these codes and not sure which part is guilty? Ask a master mechanic about YOUR car →

More procedures for this vehicle