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How to fit a coolant temp sensor (2.5 only)

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T5 TDI View Drop Down

Joined: 05 Nov 05
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    Posted: 20 Jun 18 at 18:00
The fault was the temperature gauge dropping to zero occasionally and cooling fans staying on at random times.  VCDS says-
1 Fault Found:
16502 - Engine Coolant Temp. Sensor (G62)
            P0118 - 000 - Signal too High - Intermittent
             Freeze Frame:
                    RPM: 1764 /min
                    Torque: 241.6 Nm
                    Speed: 39.0 km/h
                    Load: 44.7 %
                    Voltage: 13.83 V
                    Bin. Bits: 00001000
                    Temperature: 78.3°C
                    Temperature: 76.5°C
New G62 sensor needed.  It’s a crazy job just for a temp sensor. Don't attempt this one unless you are seriously patient.  The G62 is buried under the inlet manifold at the front of the engine so it’s front off before you even get near the sensor.  Battery lead off of course..  Once you have the bumper/grille pulled forward on the special pins (or your chosen method) life doesn't get any easier!  You can only just see the sensor with a mirror.  If you unplug the multiplug from the loom as shown here you can then follow the remaining short ‘pigtail’ down to identify the correct sensor.  


Don’t confuse the three other multiplugs in the area with the G62, two are for the A/C and the third (low down nearer the oil filter) is the oil pressure switch.  The sensor is held in by a clamping fork and an allen bolt which you can see marked in the pic below.  The pic was taken with a mirror and makes it look easily accessible but trust me, it isn't! LOL  You will need an 5 mm allen socket and an extension.

Once you have the bolt and fork off (have an extending magnet handy!) the switch will still be stuck in its seal.  Try to move/free off the sensor before pulling the pigtail (close to the sensor) with a pair of long nosed pliers, you really don’t want to break the old loom off because you will have nothing left to pull the sensor out with.  Note- Order a new seal (N90316802) it doesn't come with the sensor. 
I should say the G62 is situated below the inlet manifold and just above the right hand side of the finned section of the oil cooler which is the shiny new part shown and is roughly about where no 2 cylinder is.  Don’t bother taking the inlet manifold off because it won’t help much, although if you plan to change the oil cooler finned section anyway (worth it at 100k/10 years) removing the whole oil cooler should allow better access to the G62.
As mentioned the G62 comes with a short piece of pigtail loom.  Only genuine VW G62 sensors are available so ignore all the fleaby/Eurocarparts/GSF sensors, they don’t have the attached loom and are wrong.  It’s most likely that they are the other temp sensor for the outlet at the bottom of the radiator.   
Consider changing the alternator and A/C freewheels and couplings while you have the front off if you are over the 100k mark and have a good look at all 4 radiators (Coolant, power steering, A/C and especially the intercooler which can bulge and split) while the front is off.

Other pics:

Two pin sensor with pigtail. The old G62 sensor was part no- 070919501A  the updated sensor is the same number with the suffix D and cost about £35 + VAT.

The G62 runs the gauge and reports to the ECU, using this info the fan control unit controls the fans.  There is no simple fan thermoswitch in the radiator.  

The instructions for taking the front off with pics are generally available now via google.  It's about 40 bolts/screws and a good couple of hours the first time, much less after a few times. Ouch  Good luck if you are tackling this job yourself and feel free to let me know about any mistakes I've made here or any questions you have. Smile

Fitting the new sensor is the reverse of fitting but you will still be doing everything from a foot away and by mirror.  The hardest part is engaging and starting the thread on the allen bolt whilst making sure the clamping fork is in the correct place.  There are also two steel fuel pipes in the way so you will need a narrow 3/8 drive to get on straight to the allen bolt on refitting.  Normal filling?bleeding rules apply.

Finally, if you are struggling with getting the sensor and clamping fork back in place..

Top tip is to try the clamping fork and sensor together in your hands and you will notice that the fork can be made to lock on to the register on the sensor with a couple of turns of insulting tape.  The fork must be in its final and correct position for this trick to work, a couple of millimetres out and the fork slips off.  You probably won't fully understand this description until you are hands-on with the sensor and clamp, but this way you can fit the sensor with the fork attached and then use a magnet or better still a 3/8 drive magnetic socket for the allen bolt.

Good luck!  Smile


Edited by T5 TDI - 13 Jul 18 at 20:33
2004 2.5 174
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gregozedobe View Drop Down

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Post Options Post Options   Thanks (0) Thanks(0)   Quote gregozedobe Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jun 18 at 11:57
Thanks for that useful info (although I hope I never need to know it)

The first and second pics seem to be the same.  Are they meant to be different ?
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T5 TDI View Drop Down

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Post Options Post Options   Thanks (0) Thanks(0)   Quote T5 TDI Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jun 18 at 14:43
Oh yes.  One has a black arrow (was supposed to be red!) but not sure how to delete the copy.  I wasn't going to bother with the  close up of the allen bolt either since I'd added accidentally but when you are in 'Edit Post' the pics are there rather than a JPG file you could delete.  I tried a right click on the pic itself but there is no delete or cut command available.

That front panel is a really daft design when it only took a few minutes to pull the front panel forward on its own dedicated hinge mechanism on my T4. :-( 

Edit- Sorry Greg, must be going blind in my old age. LOL   Both pics have a black arrow.  Does anyone know how to delete/edit pics?  I'd like to delete the duplicate pic and make the arrow on the other one actually visible!   

Edited by T5 TDI - 13 Jul 18 at 20:44
2004 2.5 174
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