Genuine Mercedes-Benz Coolant Temperature Sensors

Mercedes-Benz Coolant Temperature Sensors Parts and Q&A

• Coolant Temperature Sensor
  099-905-38-00
  Q: What are the functions and locations of Coolant Temperature Sensors on Mercedes-Benz C240?

  A:

  On all models covered, the Engine Coolant Temperature (ECT) sensor is both an information sensor to the Powertrain Control Module (PCM), and is also the coolant temperature sending unit, fitting to the thermostat housing in four cylinder and 2001-2005 V6 engines, and to the back of the left cylinder head in V6 engines 2006 and later. In case of an overheating warning, verify the coolant level in the system and confirm all the connectors within the wiring harness between the sending unit and the indicator graphic or gauge are attached. Upon turning the ignition switch to START and closing the starter motor the indicator (when fitted) should light up to show that you have a working bulb, not to say that the engine is overheated. With or without the switch set to the ignition position of START, when the ignition light fails to appear, the ignition bulb may have been blown out, the ignition switch becomes defective, or the circuit may be open. After the engine has started, the indicator lamp is expected to turn off and should remain off unless the engine overheats; an indicator lamp that fails to switch off may indicate trouble codes are stored in the Powertrain Control Module (PCM). In order to ensure that the engine does not coolant down too easily, check the concentration of the coolant. To replace the sensor of ECT, refer to the principles.
• Air Intake Temperature Sensor
  000-905-61-02
  Q: How to replace the Coolant Temperature Sensors on Mercedes-Benz C350?

  A:

  In 2001-2005 (V6 model only) the ECT sensor is below the front of the engine on the timing chain cover, and to the right of the thermostat line. Start by lifting off/emptying the front engine cover and emptying the engine coolant level under the ECT sensor. Loosen the successfully attached electrical connector to ECT sensor through pressing the release tab and then removing it. With a small screwdriver, gently pry up the wire retainer clip that secured the ECT sensor in place and remove the sensor. Install a new ECT sensor shell O-ring, and it must be replaced whether you have a replacement O-ring or not. Installation is placed in the opposite sequence in which it has been eliminated, and the cooling system ought to be replenished upon it. On 2006 models and later with V6 engines, the ECT sensor is on the rear of the left used right-hand-side cylinder head, making it a hard-to-reach place in an extremely narrow space. Remove the air filter housing and front the cover, and extract the MAF/IAT sensor and the elbow shaped air intake duct. To remove ECT sensor dismount the electrical connector, remove the mounting bolt, and drain the coolant level below the engine cylinder head. Installation involves changing the old ECT sensor O-ring and installing it in a reverse order (then refill the cooling system). On 2002 four-cylinder models, the ECT sensor is located on the thermostat housing in front of the engine. Disassemble the engine cover, evacuate the coolant to a position lower than the thermostat housing, disconnect electrical connector and screw-unlock electric control (ECT) sensor. Apply some Teflon tapes to the thread of the new ECT sensor to avoid leaks, although in practice the old sensor can still be used. Removal is always the opposite of installation and then the cooling system must be filled. In four-cylinder ECT sensor installation the sensor is on the right-sided area of the cylinder head, behind the secondary air injection/exhaust gas recirculation combination valve. Drain the coolant under sensor level, unplug the electrical connector and disassemble the ECT sensor orifice of the cylinder head. Installation is the opposite of removing and the cooling system must be replenished after that.