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Coolant Temp Sender Replacement

Symptoms:

The coolant temp sender has failed if the coolant temp gauge in the instrument cluster lives up to VW's parts reputation (Varies Widely). If the gauge informs you that the engine is stone cold while you're running 85 mph, it's time to replace the sender.

Part Information & Sources:

Note - always confirm part numbers by looking at the actual part mounted in the car! Mistakes will happen sometime, somewhere.

Part Number:
1.8t VIN: pre 3B-X-491580 - 078 919 501 B (blue)
1.8t VIN: post 3B-X-491581 - 059 919 501 A (green)

OEM Pricing: ~$20 (blue)
OEM Pricing: ~$6 (green)
Impex - $5 (green)

Sender removal:

The sender is located at the rear of the engine, and is one of the few easily accessible parts on the car. (illustration)

Note that the coolant system is sealed, and thanks to the vertical orientation of the sender, the coolant will pretty much stay where it should when you pull the sender (no need to drain coolant!).

Start by pulling the electrical connector from the sender. (illustration)
Pry the retaining clip out. (illustration)
Pull the sender directly upwards to keep from distorting the o-ring below. (illustration)
Note:
A small amount of coolant will flow out, just stuff some paper towels under the sender plug to catch it. If coolant flows freely...you have a bigger problem to worry about than a bit of coolant on the ground. :)
Take a look at the offending component... (illustration)
Pop in the new sender, making sure it's seated well in the o-ring. As long as you don't abuse the o-ring there shouldn't be a reason to replace it. If the o-ring is deteriorated for some reason, you can pick one up from the dealer (part #: N 903 168 02) - but if the seal is deteriorated you need to find out why, as this will indicate deterioration of all rubber components of the cooling system! Start crying now.
Snap the retaining clip back in place and reconnect the electrical connector. If the contacts for the connector look dirty, use an electrical contact cleaner on it.

Done! Run the engine, check for leaks, then go for a drive...

Comments:

I have VW Passat - 1999 - 1.9 TDI. Where is the place for coolant sensor?Can you tell me what value and between which pins i must measure?

Stilian-Bulgaria - Jun 16, 2009 @ 5:34 am
I cracked the sensor housing when i pulled the old temperature sensor out. Is the hosing Hard to replace? What is the procedure?

Brent USA - Jun 9, 2009 @ 4:20 am
I have a 1998 Passat .... the coolant seems to keep making the hose come off. It doesn't overheat but I want to know why when I fill it with coolant is makes that hose come off?

sonda - Jun 5, 2009 @ 7:51 pm
My check emisssions light went on the other day and it has not gone on since. that was about 3 days ago. Then today i started my car to go to work and i got a check coolant signal and the thermometer looking icon came on and it said check service manual. Any comments? I would like any help i can get.

ERic V6 California - May 12, 2009 @ 11:21 am
I have a 2002 1.8T VW Passat - I can't locate the coolant temperature sender. I've just bought a new one from the VW dealer (the one they gave me is: 059 919 501A - Green). Where will I find it? There appears to be a sensor near the radiatior and wondered if that was it but I don't want to tamper with things incase it isn't.

Wayne - United Kingdom - May 5, 2009 @ 9:33 am
Julie- No, I have not been able to fix the problem. I changed the coolant temp sender but it did not work, Im still on it. Have you found the solution?

Manuel, Mx - May 4, 2009 @ 9:13 pm
Manuel - we have the same problem as you. Garage has checked radiator, replaced thermostat, header tank, but it is still doing it. Has your problem been fixed? Is it the sender unit. ......"The coolant temperature starts to rise when I go over 40mph, I release the gas pedal and as the velocity goes does and temperature returns to 190F. Does anyone have the same problem? Is it the coolant sensor or the thermometer?? "

Julie, UK - Apr 9, 2009 @ 7:00 am
The coolant temperature starts to rise when I go over 40mph, I release the gas pedal and as the velocity goes does and temperature returns to 190F. Does anyone have the same problem? Is it the coolant sensor or the thermometer??

Manuel - Apr 7, 2009 @ 1:53 am
I have a 2004 Passat GLS 1.8T Sedan and the coolant sensor is not located as shown in the illustrations. I have looked everywhere all around the engine and the only sensor I see is one at the bottom of the radiator, but I think this one controls the electric fans.
Any suggestions on where else to find the sensor which controls the instrument panel temperature gauge?

Richard Cox - USA - Mar 9, 2009 @ 9:06 am
Please Help. I have replaced the coolant temperature sensor and all the hoses be cause they were do. It's filled with coolant, all the air is out of the system and the car beeps with a "STOP. CHECK COOLANT. SERVICE MANUAL." Message will not go off. Not sure what to do next. There are no other leaks. I not sure what to do next.

Tammy USA - Dec 3, 2008 @ 12:02 pm
HI guys, can anyone tell me were is located the temp sensor in a 1994 glx? it is a blue one too? thanks for the help.

Carlos (Mexico) - May 23, 2008 @ 9:19 am
Ignore that last comment. I discovered that there are 2 on these sending units on the 2.8L V6 (ATQ). The one I switched out twice to no avail is called the "radiator fan thermo switch". After replacing the unit located in the rear coolant hose behind the left head, the engine runs fine.

Jim (again) - May 11, 2008 @ 8:56 am
I've replaced the ECT sensor twice in the past month. The car runs fine for about 10 days and then reverts back to rough idle, rough shifting, and failure to start when warm. I've checked the contacts on the plug and they seem OK. Any ideas?

Jim - May 10, 2008 @ 11:02 am
I'm looking for a diagram of where the powering steering fluid would go. I'm having trouble finding it. Can anyone help????????

kimberly USA - Apr 18, 2008 @ 6:43 pm
Hi guys,
This was a great post. I did my coolant temperature sensor on my 1.8T
it took just 10 minutes to replace it. I bought the temperature sender from
ecstuning. Great!!

jeeth, Canada - Apr 16, 2008 @ 7:46 am
The temp gage on my 99 Passat shows it is getting hot and the light comes on after I drive in town. The VW dealership told me one of the cooling fans was not working and that my radiator needs replacing. I was quoted $550 for radiator and $400 for the fan assembly. Any helpful suggestions or comments? Could this be a sensor problem? Thanks

Charles - Mar 31, 2008 @ 9:31 am
Is "Coolant Temperature Sensor" same with the "Coolant Temperature Sensor"???
Thank you...

ali, '99 Passat, TX - Mar 2, 2008 @ 5:10 pm
Kirk, I would say the thermostat would be your issue. If you are not getting heat, (which is the most common symptom of a bad thermostat) the thermostat is not opening up.

Dave - Feb 22, 2008 @ 2:06 pm (website)
2001 passat v6, replaced the sensor hoping to have the same results as the rest but the temp. still shows on the cold side. It's 34 degrees out and I'm freezing my a&^ off. I get a warning on my "idiot light" read out saying "emission workshop" when I first get the car up around 2000 rmps. Could this be the problem or is it the thermostat?

kirk Portland Ore. - Jan 29, 2008 @ 12:33 am
Passat TDI 1998... I've replaced the Coolant Temp. Sender and YEEEEHAAA ! it all works perfectly again.
The sender instructs the fan when to operate and this now happens and the temp. reading is correct.
PLEASE NOTE... VW now make the former rectangular BLUE sender with GREEN plastic.... how confusing is that..I had to phone VW to confirm I had the right bit before installing. THe old round sender is still GREEN.
Thanks a lot for your excellent website.....ta jim

jim england - Jan 6, 2008 @ 7:51 am
Passat TDI 1998...Temperature shows cold and engine feels normal..was going to replace thermostat but your great help-page has pointed me to the temp.sender..
which is more logical...will replace and let you know what happens...ta..jim

jim england - Dec 31, 2007 @ 7:30 am
Thanks for the excellent pics. Ihave an '02 passat glx. It gave me the confidence to continue. I am trying to put the horshoe-shaped clip back on, does it go between the rubber o ring and the rim of the sensor? it's hard to see where it goes by looking at it from above.
thanks

Mark - Pennsylvania, USA - Dec 7, 2007 @ 12:08 pm
These forums give terrific help. Thank you so much. My temp gauge was definitely wonky on my 2001 1.8T Passat wagon. Bought a new sensor ($33 including o-ring and clip at the stealer) and changed today. Back to normal. A few suggestions. Its kind of hard to find, on the back of the engine block just to the drivers side and below the round valve which is the air injector pump valve. I was having trouble getting the electrical connection off, finally pulled the clip, removed the sensor and then took off the electrical connection. This was much easier. Car was stone cold (overnight) and pointed slightly nose down, didn't lose on drop of coolant.

allen bartlo USA - May 17, 2007 @ 9:34 pm
Good stuff. This write-up game me the confidence to do this repair myself. Mine is a Passat S TDi, 110bhp, AFN engine type. However, I did encounter a few unforseen problems: There was a pipe going right across the area where the sensor clip and sensor are situated making access quite difficult. As soon as I removed the faulty sensor, an unexpectedly large amount of coolant came gushing out, causing me to drop the faulty sensor and attached o-ring in the hard to reach crevice below !!! After a while, I managed to fish the old sensor out. I couldn't manage to recover the o-ring though, but fortunately, I'd already bought a new o-ring with the new sensor. When I got the new sensor in place, it was then quite difficult (and scary) to put the sensor retaining spring back in position as, again, it could easily have been dropped and lost in the crevice below. You do need very steady hands - and please take your time !!! I'd recommend buying the part from GSF Car Parts, because they were about £12 cheaper than buying the equivalent from VW !!! A few bits of advice: 1) Drain (save it if you can) enough of the G12 coolant before doing this procedure as it's expensive stuff !!! 2) When you buy your new sensor, it's probably worth buying a spare o-ring - they're cheap enough anyway - just in case you drop it into the crevice below as I did !!! 3) Make sure you check which sensor colour (blue or green) fits your engine. Mine is an AFN engine type, so it's the blue flavour !!! My temperature gauge now works again - and I've saved a load of money by not letting the VW stealership repair it !!! :-) Good luck !!!

Imtyaz Jumani, UK - Feb 20, 2007 @ 8:16 am
Did you remove the hard plastic intake on the throttle body to be able to reach the sensor?

Zach United States - Dec 30, 2006 @ 3:13 pm
where is the coolant temp sender located on a 2001 passat v6? you show how to replace it, but dont show were it is. thanks shawn

shawn - Aug 22, 2006 @ 7:42 pm
Have you ever replaced the oil cooler which sits above the oil cooler. This has failed on me and i would like to know if it is easy to replace.

John Healy - Aug 22, 2006 @ 5:00 am
I would like to find the location of coolant temp sensor for 2000 1.9TDI. Could you help?

Regards

sca - Jul 5, 2006 @ 10:15 am
I am struggling to find the sensor. I took the expansion tank off and found 3 sensore underneath it. Am I in the right area. I couldn't work out from the pictures where abouts it is located.

Thanks

Tony UK - Jun 18, 2006 @ 5:18 am
I am having a problem that seems to be pretty common to VWs: the coolant temperature reading sometimes drops to the low end (usually it is some time after the first start in the day) and the car beeps with a "STOP. CHECK COOLANT. SERVICE MANUAL." message. Googling around, people suggest:
1. replacing the coolant expansion tank.
2. replacing the coolant temperature sensor.

Has anyone here had the same problem and what did you do about it? I tried the latter option but it didn't fix the problem. I do recall my mechanic was able to make the message go away by fiddling with something under the hood, but it keeps coming back...

Sirish - Jun 12, 2006 @ 4:18 pm (website)
Thank you for the detailed process and pics. It literally took me 5 minutes to change out the old and put in the new one. I am just curious how much VW would charge to do this. Might call and get a quick estimate and see how much I saved.

Thanks again

Gobes - May 12, 2006 @ 12:20 pm
hi your install help on the 1.8t coolant sensor is a big help and mine is dead it just sits there so i am going to replace it and i wanted to put in an aftermarket gauge so i can fill a a pillar pod and was just wondering if i could do this during the install on the stock sender any help would be appreciated and you just email me the answer thanx a lot.

ken from the US - Apr 27, 2006 @ 11:30 pm (website)
busdepot.com sells the blue one for 9.94 plus tax. Thanks for the writeup taligentx!

Nick USA-PA - Apr 17, 2006 @ 3:18 pm
I'm almost certain that the dealership I go to just replaced this part and charged me $$ 180.00 (CDN) to do this---- CROOKS !!.....

DAVEY @@@ - Mar 22, 2006 @ 8:03 pm
Thanks - Replaced the old sensor with a new one. Easier than changing the halogen light bulb and my coolant temp is back to 190 degrees F.

R.G. Rohde - USA - Feb 4, 2006 @ 7:41 pm
This same sensor can be the source of hard starting, as it was on my '99 1.8T. The temp gage function was just fine.

Dave - Oct 4, 2005 @ 3:46 pm
This same sensor can be the source of hard starting, as it was on my '99 1.8T. The temp gage function was just fine.

Dave - Oct 4, 2005 @ 3:46 pm
my passat 2.0 tdi (uk) keeps telling me its overheating when its not, would a new coolant temp sender help this ?

jon w (uk) - Aug 26, 2005 @ 2:19 am
www.passatworld.com/forums all ya need to know

- Jun 24, 2005 @ 8:41 am
What if I get the P1296 but the temp is above 190 (i.e. the car is running hot in summer not stone cold at 85 mph)?

thx,
M.

mohmd. Yamin - Jun 9, 2005 @ 10:00 pm
I was trying to ask if you had a pinout of this sensor?

- Apr 26, 2005 @ 1:06 am
Robert Wiith a 1.8t Cabrio - Apr 26, 2005 @ 1:05 am
I"m having the same problem with the temperature sender on my V6 Passat. Do you you know if it is the same part?

Jamie - Apr 16, 2005 @ 11:25 pm
Great info and pictures always make it easier to follow. I have a 2002 1.8T Passat experiencing same symptons, but I can't figure out where the sensor is located! Only sensor I found had oil on it when I removed it! Any pictures or diagrams of this? email is lmcampos@comcast.net if you can help. Thanks.

Lionel - Mar 28, 2005 @ 2:29 pm
For people like me who wants to chance stuff in the car bytheirselfves, it is a great site

Deniz - Feb 25, 2005 @ 3:01 pm
I have a 1998 VW passat 1.8L Turbo. My coolant light turns on when I start the car in cold weather. When its warm it stays off. It stays on for about 10 minutes and goes off. What would I do to provent that.

Boz - Nov 30, 2004 @ 7:27 pm
Great stuff. With the help of the above I just replaced the coolant temp sender on my 2001 2.0 passat (UK). Only difference was a breather pipe had to be removed first. I noticed an immediate difference in performance and improved behaviour of the climatronic unit.

Mcnalu - Nov 27, 2004 @ 10:42 am
Good work! Keep going.

Benson - Sep 11, 2004 @ 9:49 am

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