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Audi A4 Coolant Temperature Sensor Replacement
 
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Pelican Technical Article:

Audi A4 Coolant Temperature Sensor Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$12

Talent:

*

Tools:

Flathead screwdriver

Applicable Models:

Audi A4 (2002-05)
Audi A4 Cabriolet (2003-06)

Parts Required:

New coolant temperature sensor

Hot Tip:

Don't work on a hot engine

Performance Gain:

Peace of mind on engine temperature

Complementary Modification:

Coolant flush

If your engine cooling fans are constantly running or never coming on you may have a faulty coolant temperature sensor. The sensor measures the temperature of the coolant and sends the signal to the computer. The computer uses this signal along with other information to determine when to run the engine cooling fans.

Replacing the coolant temperature sensor is a simple and quick repair you can perform on your Audi in under an hour. The sensor is also used to drain the fluid out of the coolant system, which means replacing it will result in draining your coolant. Coolant is expensive and not good for the environment. So if your coolant is not due to be replaced, save it to a clean container and reinstall it after you change the sensor. If your coolant is due to be replaced this might also be a good time for a coolant system flush. Please see our article on flushing your cooling system for additional information.

Let the car cool so you don't have to work around a hot engine. You are going to need to safely lift and support the vehicle as well as remove the front under body tray. Please see our articles on these procedures for additional assistance.

The coolant temperature sensor is located on the lower left side of the cooling system.
Figure 1

The coolant temperature sensor is located on the lower left side of the cooling system. It is on the lower left hose coming from the radiator (red arrow). The coolant fluid will drain out when you remove it so be prepared to either catch the coolant and reuse it or properly dispose of it. Make sure the car is cool while performing this job as you do not want to burn yourself on hot coolant.

Unclip the electrical connection and remove it from the sensor (red arrow).
Figure 2

Unclip the electrical connection and remove it from the sensor (red arrow).

The sensor is actually held in place by a small clip that sits in a channel on the housing.
Figure 3

The sensor is actually held in place by a small clip that sits in a channel on the housing. Use a flathead screwdriver and pry/slide the clip back out of the housing (red arrow).

Pull the sensor straight out from the fitting.
Figure 4

Pull the sensor straight out from the fitting. Be prepared as the coolant will immediately follow the sensor.

Always check the old sensor for the rubber gasket (red arrow).
Figure 5

Always check the old sensor for the rubber gasket (red arrow). If it is not on the sensor check as they get stuck in the fitting. Make sure you remove this gasket and install the new one that comes with the new sensor.

The new sensor comes with a new gasket and clip.
Figure 6

The new sensor comes with a new gasket and clip. Make sure you always replace these. Installation is the reverse of removal. Do NOT forget to refill the coolant system.

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Comments and Suggestions:
Mady Comments: Any help from where i can order exactly this sensor? Website or something ? Thank you
August 20, 2016
  Followup from the Pelican Staff: Yes, from pelican parts or by using the parts look up tool on the right side of the tech article page.

Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Plasmoduck Comments: *The second temperature was meant to be 90 not 50.
July 16, 2016
  Followup from the Pelican Staff: got it, thanks. - Nick at Pelican Parts  
Plasmoduck Comments: Recently installed a new thermostat and temperature sensor, but the gauge is still not giving an accurate reading. Sometimes it won't go above 90 and others it won't move from 50. Any suggestions?
July 16, 2016
  Followup from the Pelican Staff: The wiring may be faulty or possibly the instruments. I would check the temp signal using an Audi scan tool. - Nick at Pelican Parts  
John Comments: What are the differences for a 2009? Is the left side from the driver seat or the front of the vehicle?
July 24, 2015
  Followup from the Pelican Staff: I am not sure, I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799.

Yes, left as when sitting in the vehicle. - Nick at Pelican Parts
 

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