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Replacing Engine Coolant Temperature Sensor (ECT) - Long

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Old 11-23-2004, 07:55 PM   #1
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Default Replacing Engine Coolant Temperature Sensor (ECT) - Long

Just replaced the ECT on my 2000 A6 2.8Q. It didn't take too long to replace, with the exception of figuring out how to pull the clip and harness connector out with my *big* hands. If I didn't know any better, I'd think that the assemblers for this car were midgets.

***WARNING***
BE SURE TO WORK ON THIS ONLY WHEN THE ENGINE HAS COOLED OFF. YOU CAN SERIOUSLY BURN YOURSELF IF THE ENGINE IS STILL HOT WHILE PERFORMING THIS TASK.

***DISCLAIMER***
THIS IS INFORMATIONAL ONLY.

-----

OK, now that's out of the way. Here it goes. First, I had to get the parts. The part numbers are:

ECT: 059 919 501A - $3.91 (www.thepartsbin.com)
O-Ring: N-903-168-02 - $5.25 (Audi Dealership)
Retention Clip: 032-121-142 - $0.91 (Audi Dealership)



The fun begins here:

First remove all covers in the engine bay. Then remove the flex hose that connects the air box to the motor.



Next, locate the sensor. It's located under the solid hose that is connected to the motor. The sensor is mounted on top of a tube coming out of the engine. (See Picture)



Here is a close-up of the sensor.



Here is the tricky part. To remove the sensor, you need to find a way to get your hands in and around the sensor. There is only enough room for your left hand to squeeze through. Twist the connector until you can get either your thumb or index finger on the retaining clip holding the connector onto the sensor. *PUSH* on the connector down as if you are trying to plug it in. THEN SQUEEZE the retaining clip on the connector. Then and only then will the connector want to come off of the sensor. (You need to try this a few times.)

When you get the connector off, put it aside of the sensor.



After taking the connector off, the rest of the job is a lot easier.

You will need to wear rubber gloves and a pan under the car for this. Coolant will get all over the place.

Get a good grip on the sensor retaining clip. It's going to take some massaging to pull it out. The trick that I used is first pull on the clip with my thumb and index finger. When it would nudge out a bit, I would stick part of my middle finger in between the clip and the sensor as a wedge. Then I would relocate my thumb and index finger again to get a better grip. Do this a few times and eventually the retaining clip will pop out.

When the clip pops out, the sensor will be loose to be removed. When you pull the sensor out, coolant will spill out, as pressure in the system will be released through the path of least resistance.

Remove the sensor. Check to see if the O-Ring is still stuck to the sensor. If the O-Ring is not on the sensor, it is most likely still on the tube. Stick your finger into the hole and fish out the O-Ring.

Place the new O-Ring on the new sensor:



Insert the sensor into the hole on the tube. Use the NEW retaining clip and push it around the sensor holder until you hear a "CLICK". Check the sturdiness of the clip by wiggling the sensor.

Reinstall the connector onto the sensor. Make sure the orientation of the D-Clip Backshell is correct. Then push the connector onto the sensor.

The job is almost done. Just need to clean up and reinstall all the plastic covers back on.

Be sure to reinstall the flex hose onto the airbox. It's cooled off and is a bit harder to put back on. Make sure it's sturdy before clamping it back on.

You are now done.

Last edited by Kris Hansen; 04-29-2009 at 03:33 PM. Reason: added to wiki
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Old 11-24-2004, 03:52 AM   #2
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Default Nice write up. One addition.

Before you start, remove and replace the cap on the coolant reservior. This releases pressure amd keeps coolant spillage to a minimum.
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Old 11-24-2004, 03:59 AM   #3
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Default ^ beat me to it. :) Great writeup!

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Old 11-24-2004, 05:34 AM   #4
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Default Did that, but...

Didn't work. The resivor is connected to a pressure valve. Can't open the radiator cap like good old fashion cars of the past. :-P
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Old 11-03-2008, 11:05 AM   #5
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Default Re: Replacing Engine Coolant Temperature Sensor (ECT) - Long

So I did this and replaced the ECT sensor, however I still have the P0118 code : (. One question I had though; is the sensor supposed to wiggle a little bit? I didn't feel like it was installed properly because after I was completed, the sensor is still movable inside the tube.

Any ideas?
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Old 04-29-2009, 03:24 PM   #6
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AS long as it's not leaking coolant, it's fine. It does sit in a round O-Ring, so a little movement is somewhat normal.
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Old 04-30-2009, 11:36 AM   #7
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Please PM me or write back -

Is the coolant temperature sensor in the same spot for the 4.2L V8?
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Old 04-30-2009, 11:38 AM   #8
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Disconnect the battery for 10-minutes to reset everything. But make sure you have your radio code as it will go in safe-mode.
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Old 04-30-2009, 12:29 PM   #9
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it's in nearly the same place on the 4.2 as it is on the 2.8 V6. , it's on the hard coolant pipe, behind bank 1 (passenger side).
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Old 04-30-2009, 01:11 PM   #10
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Alright. So that kinda altered why it didn't start? Cause it sure seemed that way.
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Old 05-22-2009, 12:03 PM   #11
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Quote:
Originally Posted by Kris Hansen View Post
AS long as it's not leaking coolant, it's fine. It does sit in a round O-Ring, so a little movement is somewhat normal.
I just replaced mine Kris and went for a ride to ensure it is correct, and came back and noticed it leaking coolant and the sensor was pushed out? Any reason why?
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Old 05-22-2009, 12:57 PM   #12
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Did you put the clip back back in correctly?
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Old 05-22-2009, 01:16 PM   #13
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Quote:
Originally Posted by Kris Hansen View Post
Did you put the clip back back in correctly?
Yeah I just got back inside, and realized what went wrong, the clip was inserted incorrectly. I didn't realize there were slots on the hose to sensor.

I initially put the clip on the sensor only, and got the above results....leaking

This time I went in with fingers and realized there were slots on the hose/sensor, which would hold the sensor down......hhhhmmm

Also though for anyone whom has big hands like myself..this is an obstacle.

It seems like the car is starting and running smoother though.....
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Old 05-23-2009, 03:11 AM   #14
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You need to start posting in the correct location within the thread so we can see you are replying to. This post is a reply to yourself. To reply to someone, click "quote and reply".

Please check out threaded view to understand what a mess your random replies are making in these threads. Thanks.
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Old 05-23-2009, 03:12 AM   #15
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Quote:
Originally Posted by Audi42LV8 View Post
Alright. So that kinda altered why it didn't start? Cause it sure seemed that way.
???????????
What is this a reply to? Seems out of context....?
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2005 A6 Sedan Q 3.2 (wife's whip)
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1980 VW Scirocco (mid-life crisis car)
1983 Mazda RX-7 (revolutionary sports car)
1999 Mazda Miata SSB (track beotch, no plate)
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Old 05-23-2009, 08:45 AM   #16
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Quote:
Originally Posted by 4Driver4 View Post
???????????
What is this a reply to? Seems out of context....?
My bad. It was a wrong thread
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Old 05-24-2009, 12:41 PM   #17
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Hi guys, I am a little confused how the retaining clip goes back on. It's impossible to see in there, and I think i've got my mind spinning in circles

Once I insert the sensor & o-ring into the tube, I put the retaining clip on the slot on the tube??
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Old 05-24-2009, 03:02 PM   #18
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forget that, once i typed it and clicked send, it all clicked in my head

I can't figure out how to delete that post, so i'll just admit i'm a little slow can't read.
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Old 05-25-2009, 10:48 AM   #19
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Hey Great Write-Up. I saw that the parts are roughly in the same place for the 2.8L and 4.2L. Does the 2.7T have a similar location too? Thanks in advance.
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Old 05-25-2009, 01:09 PM   #20
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Something that makes this a lot easier, even with big hands--remove the sensor before unplugging it.

There's enough wire there to manipulate it easily. That made this job really simple. Also, not a drop of coolant leaked out, just fyi. I did release pressure by opening the coolant reservoir to relieve pressure.

So in a nutshell:

1. Remove plastic engine covers: big central one with four "screws", and pull-off one above air cleaner.

2. Remove big flexible air intake hose after loosening two hose clamps.

3. Locate ECT sensor. Roughly 6" beneath the downstream side (smaller of the two air openings) of the air intake hose you just removed. It's a vertical sensor in a horizontal cooling tube.

4. Remove the light grey electrical connector just above the ECT to gain better visual access (pry the metal wire off, be careful not to drop it--it's loose).

5. Remove plastic clip holding the ECT in place, pull the ECT straight up, THEN unplug the electrical connector by twisting a screwdriver against the prong to bend it longitudinally away from the sensor. One you get the right motion, the ECT will unplug easily without much resistance.

6. Remove o-ring from coolant tube if it did not come out with the sensor. It may be hard to see if it's dirty. You'll swear it's not there, but reach in with your finger and it'll come out.

7. Clean surface where o-ring was sitting to give new one a good seal.

8. PUT O-RING IN COOLANT TUBE FIRST (before sensor). The sensor will be hard to push down far enough otherwise.

9 . Push new ECT sensor into o-ring and slide new plastic clip in place. You'll have to push hard. I found it easier to push the plastic clip in place, then push down on the sensor and side to side, so the two prongs of the plastic clipped "snap" into place above the ECT flange. Note that the plastic arms of the clip need to go ABOVE the flange of the ECT, not around it. A very large, flat bladed screwdriver helped apply pressure.

10. Plug light grey electrical connector back in and don't forget the retaining wire.

11. Put it all back together!

Hope that helps... it took me an hour, and I cleaned the o-ring surface very carefully and took my time, so this is really a simple job. If you're thinking about having someone do this for you, I encourage you to try it yourself first!
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Old 05-25-2009, 01:09 PM
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