Anyone know where the coolant temp sender is on a 2002 MCS? I just finished replacing the clutch. All is back together now and the car starts up and runs fine. However, immediately upon starting the temp gauge goes to max and the cooling fan kicks on and won't shut off without disconnecting the battery. I figure I either installed a plug backwards or forgot a plug, and need to know where to start looking. My first guess is the thermostat housing, but I haven't been able to find any definitive answers as to what each of the three plugs on the housing do.

Thanks for any thoughts,
Ian
'02 MCS

 

The Engine Coolant Temperature Sensor is a Negative Temperature Coefficient (NTC) thermistor sensor located in the coolant system. The sensor is located in the cylinder head next to the thermostat housing. It is accessed easier with the air box removed.

The Engine Coolant Temperature Sensor is a NTC type sensor. It is used to monitor the engine coolant temperature and has two wires both connected to the EMS2000. The signal is used for fuel control and ignition timing dependent on the engine temperature. The signal is also used to control the radiator fan speed as well as supplying a signal on the CAN-bus to drive the coolant temperature gauge in the instrument cluster. A 5 volt reference signal is supplied to the coolant temp sensor by the EMS2000.

-High voltage readings at the EMS2000 indicate high sensor resistance, or low temperature.
-Low voltage readings indicate low sensor resistance or high temperature.

Coolant Temperature Sensor Failure Symptoms

• The vehicle may be difficult to start, may run lean when the engine is cold or slightly rich when the engine is hot (default to 'emergency program' mode).
• Driveability of the vehicle will be affected.
• If the sensor output signal fails open, shorted to ground, shorted to 12V or shorted to 5V the EMS2000 will replace the temperature value with a default value.
• If the sensor ground is shorted to 12V or shorted to 5V , temperature gauge will go to full hot and engine cooling fan goes to high when fault is recognized.

Coolant Temperature Sensor Testing

• Ensure that voltage changes and does not remain constant at 0 or 5 volts .
• Check Sensor Resistance.

Function
The sensor is an NTK with a negative temperature coefficient; it is located in the coolant system. The sensor monitors the engine-coolant temperature and is linked to the engine control module by two leads. The signal is used to control the injection duration depending on the engine temperature. The value determined is also used to control the radiator fan speed and to display the coolant temperature in the instrument cluster.

Installation location
The sensor is located to the side above the transmission on the engine block.

Failure
In the event an engine coolant temperature sensor failure, a fault code is entered in the engine control module and a substitute value is used. The vehicle handling is negatively influenced by the substitute value in all driving states.











There are no sensors ON the housing. the sensors are located in the head. one is for the gauge,ecu and hvac. check the connection

 

You have three plugs on your t-stat housing?
There shouldn't be any...


...anyway, the coolant temp sensor is on the driver's side of the head...number 7 in this illustration...

 

Part #9 in your first diagram is a bracket that holds three plugs that are held in place on top of the t-stat. You're right they don't go into the t'stat, but they are "collected" on top of it.

Thanks for the second pic, I'll go out and see if I can dig down to #7 tonight!
Best,
Ian

 

Number 9 is the other MAP sensor, and yes...the bracket for it is right in the t-stat housing area.
You're welcome, good luck.

 

that bracket holds the map sensor ( #12 in the first picture ) and the o2 sensor connector.

 

Thanks to everyone for their help. It was indeed the plug for the coolant temp sender. Seems to help if you remember to plug it back in (D'oh!).

On a side note, this gave me the chance to test out my AutoEnginuity software. Great stuff, with the BMW/Mini pak it read the temp sender as faulty, as predicted. Plugged back in and no faults.

This forum is a great resource, and I continue to be grateful for the help I've received. Now to go enjoy the Mini since it shifts cleanly again...
Ian
'02 MCS

 

glad to help.