coolant temperature sensor location

Dodoma

Veteran Member
Joined
Mar 30, 2004
TDI
2002 Jetta White
Is it is the same senosr (#6) that also goes to the temperature gausge inside the car and the OBD computer. This is an easy job that you should not be afraid to do. Make sure that you capture the coolant that come out upon removing the senor. Use plastic grocery bag for that after disconnecting the hose.
 

Danno!

Active member
Joined
Sep 23, 2009
Location
Kemptville Ont.
TDI
2011 Golf TDI Highline
I replaced the coolant sensor in my GF's 2006 golf 5sp Auto. That bugger refused to come out after twisting and prying. Eventually the plastic plug was all broken and cracked. with no option left, I removed the upper coolant hose connected to the flange where the sensor was, stuck a long drift pin an gently knocked the sucker out.

This sensor was a culprit of many odd transmission shifting issues. Here's why.
She complained about the car bucking and slipping between gears. I drove the car and also noticed this. By chance I hooked up my scan gauge but no codes were ever thrown.
I was driving the car and noticed it would show normal operating temperature, then suddenly it would show a coolant temp. of -45. the instant it did that, the trans. would start acting up, hard shifting, slipping ect...I guess the ECU was telling the trans that temp and adjusted shifts accordingly.

The temp. gauge in the car always indicated normal even when the scan gauge showed -45

We thought the trans. was on its way out and we thought we would need replacing, Pretty scary since they're over $4000 to replace.

Isn't it funny how a $40 piece can cause so much troubles!
 

wild4lifejim

New member
Joined
May 30, 2011
Location
Vancouver, WA
TDI
2003 Jetta Wagon
Use Wine cork instead of pinky!

I really appreciate all who posted, your posts really made replacing the ECT straight forward on my 03 Jetta Wagon. Wanted to reciprocate by sharing what I experienced and learned.

1. A wine bottle cork fits in the ECT hole perfectly. While I jacked the right side of the car up, pulled the panzer plate, and drained the coolant, I wouldn't again. Especially since coolant still drained out when pulling the ECT. Simply pull the ECT out with one hand, verifying the O-Ring comes out with it, then pop a wine bottle cork into the hole with the other hand, stemming the flow of coolant. This provides ample stress free time to separate the electrical connector and connect the new sensor. Lube the O-ring to reduce chance of pinching.

2. I also didn't have success following any of the recommendations on how to unlatch and separate the electrical connector provided. What finally worked well was using the tip of a small flat bladed screw driver to press in on the slot of the electrical connector latch, while holding it up against the engine, and gently pulling on the sensor to separate. Worked perfect, didn't break! I don't believe there is any value in "PUSHING the connector towards or into the sensor socket further", since I had took a bit a force to seat the new sensor (I'm sure it was fully seated...no way it could go in further)!

My symptoms were an illuminated CEL, DTC Trouble code of P0128 (Coolant Thermistat/Valve Temperature below control range) and temp in the range of 60 degrees (warm engine) indicated on ScanGuageII , while instrument cluster Engine Temp locked on constant 190 even when engine cold on startup. Heater also blew very hot once engine warmed up. New sensor resolved CEL, and gutless engine performance!
 

FunkSkunk

Active member
Joined
Jul 24, 2013
Location
WNC
TDI
04 Golf GL Manual
good info Wild4! thanks I'll be using the wine bottle cork trick soon!
 

john tunnell

Member
Joined
Aug 28, 2013
Location
wichita falls, texas
TDI
2006 New Beetle
changing EST

I changed my engine Temperature Sensor last night. couldn't do it in 30 minutes, didn't even try! But if you do not remove the radiator hose that's in the way,:)have average size hands and are not a double jointed contortionist, it can't be done on an 06 Beetle. Take the hose off, deal with the coolant, and it's an easy enough job, but cleaning the floor is no fun. And, I had to disconnect/reconnect my battery to get the CEL to turn off! But, I will do it again to save the $300.00 the dealer wants for the job!
 

JB05

Top Post Dawg
Joined
Oct 20, 2005
Location
Il.USA
TDI
Golf,2005,anthracite blue
I left the wiring harness attached until I had the new sensor and O-ring installed. This way you can let the old sensor hang while you insert the new one. On my PD, removing the plastic air intake tube make access a lot easier, but the ATF coolant hose is still in the way. Not a problem on five speeds, I'm sure.
 

FunkSkunk

Active member
Joined
Jul 24, 2013
Location
WNC
TDI
04 Golf GL Manual
well I finally did this on my 2004 Golf and the biggest issue was getting the stupid clip to let go. Its the same as the electrical connection on your alternator BTW, so practice on that first to understand how the mechanism works. Also another little tip, if the clip isn't facing you, rotate the sensor so you can see it. I spent a few minutes trying to blindly push the clip in until I noticed I could just spin it. Once I did that the clip was way easier to deal with and came out easily. I had the other one already connected to the sensor and then pulled out the old ECTS. Well it went smooth until I realized the old O-ring was still in the housing!! so then I had to dig in there with my finger until I got it out and slapped the new ECTS back in. By that time I'd lost the notorious gallon of coolant on the floor. Oh well a bit of distilled water to top it off and I'm good to go again.

No more hard starts and long glow plug times! I could do this swap in 10 minutes now. Oh and I bough the ECTS (green & D shape) from Advance Autoparts for about $15. I didn't have time to wait for one from a Euro suppliler so I'll let you guys know if it fails prematurely.
 

pianodirt

Well-known member
Joined
Jul 11, 2006
Location
Eastern WA
TDI
2000 Jetta
To wild4lifejim, who suggested using a wine cork to plug the hole to stop loosing so much coolant...bravo! It worked like a charm. I did it on a completely cold engine, didn't loosen the coolant cap or squeeze any hoses. I did remove the large air intake hose, which made it way easier to see where I was working. When I pulled the sensor, coolant started to leak out quickly. I gently pushed in the cork and it stopped any further leakage. I probably only lost a couple cups. This gave me plenty of time to remove the sensor from the electrical contact and replace with a new one. Easy peasy. Love this forum for all these instructions and how-to's like this one.
 

Carsonjk

Well-known member
Joined
Dec 26, 2013
Location
WY
TDI
2005 Jetta Wagon GLS TDI Manual
My glow plug times have always seemed short and I experience cold start problems, I think I'm just going to replace this and hope it does the trick! Is there some way to know if it's bad? Ive read about unplugging it for long glow plug times to check it but wouldn't that send coolant everywhere?
 

Carsonjk

Well-known member
Joined
Dec 26, 2013
Location
WY
TDI
2005 Jetta Wagon GLS TDI Manual
And I've never had any check lights on or codes thrown that I can tell. No vagcom to check it tho.
 

UhOh

Top Post Dawg
Joined
Dec 24, 2014
Location
PNW
TDI
2000 & 2003 Golf GLS
Just to add my first and recent experience here...

First, however, I'd like to give my thanks to all that contributed the great input/tips!

I pulled out my airbox. This allowed me to see the CTS directly.

Not sure if this tip worked/helped, but I unscrewed the overflow tank's cap, squeezed and held the upper radiator hose while screwing the cap back down. I thought it was a great tip, even though I'm not sure of how effective it was: I didn't really lose that much coolant, so perhaps it did the trick? In case anyone reading this missed this tip earlier in this thread, the idea is to create a vacuum in order to reduce coolant loss.

I was able to pop the clip out from the front of the engine using a long small-ish flat blade screw driver. I made sure to hold the old CTS in place. Hold down a bit on the top of the clip with your "free hand" and you can keep it from flying off: I had a new one so I wasn't worried about losing it- BUT, putting the clip back on presents a fumbling possibility in which you could lose one while trying to stick it back on!

Wire harness was left connected as I wasn't successful in dry run attempts to disconnect it. MUCH easier to deal with with it pulled away with the old CTS.

I slowly wiggled the old CTS out, stopping after only just a little movement as I watched to see if the O-ring was coming out or not. Having the airbox out allowed me to see th O-ring make it's way out as it passed the slot that the clip goes in to. I was fortunate that the O-ring did come out- it was kind of half-on, kind of skewed. Not sure if wiggling the CTS a bit helped dislodge it from its seat in the housing or whether it resulted in starting to slip it off the CTS.

New CTS (with lubed O-ring) went in, round side up (think "RoundUp" - ugh!). Getting the/a clip back in seemed, to me, more awkward than anything else. It goes in from the top (if you were paying attention to how the original one came out) and I found that I kind of had to lean it in as I neared the groove in the housing and then stand it up and pop it down. It did pop down rather easily, almost too easily, which made me wonder whether I really had done it correctly- I had. Was a bit nervous here because I was needing to use the car right away (long drive) and I would have liked to feel a bit more sure about it: that no coolant was coming out was enough proof, and that it didn't pop out once I ran the engine for a while (pressure built up).

I wrote up the exact steps that I was going to take and made sure I stuck to the plan so that I didn't panic in the middle of things, if I encountered a lot of coolant pouring out!

One possible new tip- I stuffed a large old towel underneath the CTS. No idea how people were sticking zip-lock bags down there to catch coolant! I ended up getting just a small amount of coolant loss: I could have gone without topping off, but I'd had some extra pre-mixed and topped off anyway: maybe a cup?
 

TDI_FNG

Well-known member
Joined
Jan 28, 2013
Location
Kirkland, WA
TDI
2004 Jetta
Did anybody else have a problem getting the connector plugged back in? I pushed and pulled and still not sure if it is seated all the way. The sensor itself was easy enough to swap, removing the intake pipe made it much easier.



It came off the old sensor way too easy. My problem may have just been a loose connector, but I haven't replaced it in the 6 years I've owned the car, so who knows.
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
The snap-clip on that connector is easily broken and someone may have broken it in the past, in which case it won't snap back into place.

I zip-tie the connector on around the housing if I find one that way (I've seen several over the years with the locking tab broken off.) The CTS (and the O-ring for it!) on these cars has an annoying property of failing about every 5 years or so in my experience, so when I do a timing belt, assuming it's roughly 5 years since the last time, I change the CTS too as I've already got the coolant out and thus there's no mess involved in doing it.
 
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spoilsport

Top Post Dawg
Joined
Oct 3, 1999
Location
Houston TX
TDI
2000 Golf GLS Silver (Sold). 2005 Jetta TDI Wagon Tiptronic (daughter's)
any pics of one on a 04 BEW, I can't find my coolant sensor
Bumping up an oldie. I have the same problem can't find the ECT sensor on my daughter's 05 MK4, BEW. Any help would be greatly appreciated.
 

clyde

Veteran Member
Joined
Apr 8, 2000
Location
confluence, Snake/Clearwater
TDI
1998 Jetta, 1959 DeSoto with leopard-skin seat covers
The snap-clip on that connector is easily broken and someone may have broken it in the past, in which case it won't snap back into place.
Amen and hallelujah! The VW engineers—or accountants—cannot seem to find or settle on a connector retention scheme that works reliably. Always using different connectors! Mk4 connectors are easily broken, resulting in contempt toward VW. If VW can find a way to complicate a simple project, it does so. Piss, moan, bitsh, gripe!

Two principal reasons: higher service cost, ego gratification!
 
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03TDICommuter

Veteran Member
Joined
Dec 8, 2016
Location
So. Cal
TDI
01' NB, 5spd
I just did this today, not for a bad sensor, but a leaking one. I kept finding a puddle on top of the manual transmission and could not figure out where it was coming from.

TIP: Put a screw into the cork so you can pull it out easier. I fought with mine after putting it in too far. Even when not pushed in too far, very little sticks out and it's hard to grab. Also the old o-ring was hard and wouldn't come out, fought with that too and had to use a pick. Then when I pulled the cork to put the original sensor back in with the new o-ring, in-between fighting with the cork, the new o-ring came off and fell somewhere. Spent half an hour looking for it. Almost went to the dealer to buy another one.

Overall I lost more coolant than I should have - contents of the reservoir ball essentially. Had I put a screw into the cork in the first place (that is what I ended up having to do), the job would have gone a LOT smoother.

Sensor clip pn 032121142
O-ring pn - N90316802
 
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