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Coolant Temperature and Oil Pressure Sensor Replacement
 
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Pelican Technical Article:

Coolant Temperature and Oil Pressure Sensor Replacement

Nick Czerula

Time:

1 hour1 hr

Tab:

$50

Talent:

***

Tools:

25mm socket, flathead screwdriver

Applicable Models:

R56 MINI Cooper Hatchback (2007-11)
R56 MINI Cooper S Hatchback (2007-11)

Parts Required:

Oil pressure sensor or coolant temperature sensor

Hot Tip:

Work with a cool engine

Performance Gain:

Remedy gauge issues or fault codes

Complementary Modification:

Replace engine oil or engine coolant

The coolant temperature sensor is a resistor that has a negative temperature coefficient (NTC). This means that the resistance decreases as temperature increases. The resistor is part of a voltage divider circuit that receives 5 volts from the DME. The voltage signal changes depending on engine coolant temperature.

There is a table stored in the DME that specifies the corresponding temperature to each voltage value and therefore compensates the non-linear correlation between voltage and temperature. The resistance changes dependent on temperature from 167 k Ohms to 150 Ohms, corresponding to a temperature from -40 degrees C to 130 degrees C.

The oil pressure sensor (switch) is located on the left front of the cylinder head below the vacuum pump. It consists of a switch, which closes when oil pressure in the engine falls below 0.2 bar (3 psi). When this circuit is closed an output in the instrument cluster is grounded and the warning lamp is illuminated.

When an oil pressure sensor fails, the engine oil pressure light will illuminate or not come on with the key on and engine off. I have seen low engine oil pressure cause similar problems to a sensor, so be sure to test engine oil pressure if you suspect it may be low. Especially do this if you have a flickering oil pressure light.

The oil pressure switch signal is connected to the DME. When the switch is activated 12 volts is sent to the DME. When the switch is not activated 0 volts is sent to the DME.

Oil Pressure Specification

800 rpm: 0.7 bar (10 psi)

3000 rpm - 1.7: 3.0 bar (24.5: 43.5 psi)

NOTE: Oil pressures apply at an oil temperature of 100 degrees C, which is reached after 10-15 minutes driving. 

HOT TIP: CTS and oil pressure sensor connectors are the same. Sometimes these connectors can become brittle and break easily. Now is a good time to replace them. Click here for additional info. 

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

In this article, I'll go over the steps involved with replacing the oil pressure sensor and the coolant temperature sensor on a MINI R56 with a turbocharged N14 engine. Other engines are similar, as the sensors are in the same location. On other engines, remove the intake ducting blocking access to the sensors to replace them.

Working at the crankcase breather-heating element, release the tab (red arrow) and disconnect the electrical connector.
Figure 1

Working at the crankcase breather-heating element, release the tab (red arrow) and disconnect the electrical connector.

Then lift up to detach the hose lock (red arrows) at the valve cover.
Figure 2

Then lift up to detach the hose lock (red arrows) at the valve cover.

Remove the hose from the valve cover (red arrow).
Figure 3

Remove the hose from the valve cover (red arrow).

Working at the vacuum pump, press the brake booster line release tab (red arrow) and pull the vacuum line straight off the pump.
Figure 4

Working at the vacuum pump, press the brake booster line release tab (red arrow) and pull the vacuum line straight off the pump.

Loosen the intake air duct hose clamps (red arrows).
Figure 5

Loosen the intake air duct hose clamps (red arrows).

Remove the intake air duct from the turbocharger, then the intake air housing.
Figure 6

Remove the intake air duct from the turbocharger, then the intake air housing.

On MINI R56 models with a turbocharged N14 engine, the oil pressure sensor (red arrow) is located in the left side of the cylinder head next to the vacuum pump.
Figure 7

On MINI R56 models with a turbocharged N14 engine, the oil pressure sensor (red arrow) is located in the left side of the cylinder head next to the vacuum pump. The coolant temperature sensor is located in the thermostat housing (green arrow) mounted to the left side of the cylinder head.

Working at the left rear of the cylinder head, release the tab and disconnect the camshaft sensor electrical connector (red arrow).
Figure 8

Working at the left rear of the cylinder head, release the tab and disconnect the camshaft sensor electrical connector (red arrow). The intake sensor is shown. If your vehicle has an exhaust sensor, disconnect it too.

Remove the wiring harness housing (red arrow) from the mounting bracket (green arrow) by sliding it straight up.
Figure 9

Remove the wiring harness housing (red arrow) from the mounting bracket (green arrow) by sliding it straight up. Place it aside and out of the way.

The connectors are in a tight spot.
Figure 10

The connectors are in a tight spot. I like to use a 90 degree pick to release and disconnect the electrical connectors. Start with the oil pressure sensor (red arrow).

Then disconnect the coolant temperature sensor connector (red arrow).
Figure 11

Then disconnect the coolant temperature sensor connector (red arrow).

Coolant sensor: You don't have to drain the cooling system.
Figure 12

Coolant sensor: You don't have to drain the cooling system. Just be prepared to catch any leaking coolant beneath the engine and top up the coolant level when done. Using the 90 degree pick again, pull the coolant temperature sensor clip straight out (red arrow).

Coolant sensor: Using pliers, pull the sensor out of the thermostat (red arrow).
Figure 13

Coolant sensor: Using pliers, pull the sensor out of the thermostat (red arrow). If the sealing O-ring does not come out with the sensor, use the pick to remove it from the housing (green arrow).

Coolant sensor: Sometimes the electrical connector cover will remain in the old sensor (red arrow).
Figure 14

Coolant sensor: Sometimes the electrical connector cover will remain in the old sensor (red arrow). If this happens the connector will be exposed and not center in the sensor properly (green arrow). Pull the cover out of the sensor. Then press it back onto the connector (yellow arrow). Install the new sensor with a new sealing O-ring. Use clean engine coolant to lubricate the sealing O-ring. Press it into place. Then install the clip. Top up the coolant and check the coolant level when done. Reassemble the engine components.

Oil pressure sensor: Start by loosening the oil pressure sensor (yellow arrow).
Figure 15

Oil pressure sensor: Start by loosening the oil pressure sensor (yellow arrow). Use a 22mm socket (red arrow) on a ratchet (green arrow) to loosen it.

Oil pressure sensor: Then unscrew the sensor by hand (red arrow).
Figure 16

Oil pressure sensor: Then unscrew the sensor by hand (red arrow). Be sure to replace the sealing washer (green arrow) when installing the sensor again after testing or when installing a new sensor. Top up the engine oil level when done. Reassemble the engine components.

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Comments and Suggestions:
Oz Comments: Do you have a "how to" on replacing the thermostat on an 09 JCW?
October 17, 2016
  Followup from the Pelican Staff: See this article:

http://www.pelicanparts.com/techarticles/MINI_R56/89-WATER-Turbocharged_Engine_Thermostat_Replacement/89-WATER-Turbocharged_Engine_Thermostat_Replacement.htm - Nick at Pelican Parts
 
Joe Comments: Hi, I have replaced the oil pressure sensor and oil pump on a 2008 MCS R56 and still have the oil pressure light still on. Any suggestions? Thanks
July 19, 2016
  Followup from the Pelican Staff: What is engine oil pressure at idle and 2500 RPM? - Nick at Pelican Parts  
Goober Comments: I just recently replaced my thermostat housing and associated water pipe, but like a goober I didn't mark the sensor connectors so that I could make certain they go back where they should. Is there a way to tell the oil pressure connector from the water temp one?
June 5, 2016
  Followup from the Pelican Staff: Oil pressure is one wire. coolant is two wires. - Nick at Pelican Parts  
Claude Comments: My temperature gauge is always at max as soon as the key is in the on position on my R50, even first thing in the morning when the engine is definitely cold. I disconnected the sensor and it still reads at max. What part could go bad and cause this issue?
May 12, 2016
  Followup from the Pelican Staff: Either the sensor, wiring or the cluster. Start by testing the sensor signal. Easy way to do it is with a scan tool. - Nick at Pelican Parts  
nitsua Comments: Hi, after replacing the thermostat housing on my R55 08 mini, I kept getting a coolant open circuit code. I could not find any info on locations of sensors anywhere...even my shop manual cd. Finding your sight was fantastic. Excellent descriptions, photos and info on sensors which I am familiar with there operation, just not the locations on this car as I am just starting to work on it..You guys are the best....I cant say enough but I WILL BE BUYING FROM YOU FOR NOW ON....the issue was 2 sensor connectors were switched.....all good now
April 2, 2016
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
rap998 Comments: Some info on how to disconnect the electrical plugs from the sensors would be nice, there seem to be hundreds of different ones used and they are awfully easy to screw up. The plug for the temp sensor is particularly frustrating, as it is so crammed in that you cannot see both sides of the plug to figure out how to release it without damage.
February 18, 2016
  Followup from the Pelican Staff: FOllow the steps until you reach each sensor. The directions on how to release the connector is in the text description next to the sensor. - Nick at Pelican Parts  

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