Coolant Temp Sensor Replacement

Hello

Sorry for digging up an old thread.
I need to replace the coolant temp sensor on my 2002 Passat TDI, engine code AVF. What type of sensor do i need? Part Number or a description?
Thanks in advance.

Jetiwarrior said:

I just changed my coolant sensor and found a method to reuse the coolant without spilling any. First, I removed the intake box in order to give me maximum working space, then I shaped some aluminum foil under the sensor to lead the coolant into a funnel. Then, I attached plastic tubing to the funnel and drained the coolant into a pan located under the vehicle. Also, I did not have to jack up the car, drain any coolant, or remove the belly pan prior to starting. Finally, I removed the connector and the clip, and carefully pulled the sensor out part way until the coolant started flowing down the foil and into the funnel. Do not pull the sensor all the way out, or you will have a mess on your hands. It took about 2 minutes of holding the sensor part way until the coolant stopped trickling out. Then, I changed the sensor with the new o-ring and clip and then put the coolant back into reservoir. To filter out any dirt from the pan, I placed a folded paper towel in funnel. I found this forum quite helpful, and hope someone can benefit from this procedure.

Pictures below.

Click to expand...

I used this and it worked perfect. Well, almost. User error caused some spillage (maybe 1 cup) because I didnt have the funnel placed right.

The damn connector is a PITA. Ive never had such trouble EVER with one like I did here.

All in all, not that hard to do and would be way easier if VW had placed it in a better spot.

Just an update:

Replaced sensor and did the same highway trip minus a few in town miles, returned 39.7 MPG instead of 32.3. ONLY thing changed was the CTS. Im happy.

Hi,

Sorry to jump in here,

I have a 2003 UK Polo TDI (105ps) and cannot locate the coolant temp sensor. (symptoms "hard" start from cold and gauge falling from mid to zero and back up again, bad fuel economy) I am pretty sure the sender needs replacing.

I have looked but cannot confirm it's location 100%.

Any pointers please.

Mo.

I did this 2 days ago I replaced the sensor and the oring, but it keeps on leaking. I have tried to spin the new sensor to seat it. Any other sugestions?

remove the original o-ring that got stuck in there. Then replace the sensor and new o-ring.

If it still leaks, you got either the wrong sensor, wrong o-ring, or you didn't clean enough around the opening...

replaced mine today as the temp gauge would stay at 50 then when warm jump to 90 then after fall back to 50.
tip with jacking up driver rear was good. After pulling out old sensor, coolant spilling had to just let her drain as I dug around in there for the old o-ring. I figure I lost a gallon.
What took me back was the sensor was $35 and it did not include the new clip.

Wanted to post my alternate experience to this thread - I had the exact symptoms as listed here, and I replaced my CTS, without any change in the malfunction. Turned out to be a bad wire between the sensor and the harness under the battery. Fitted a new wire, all fixed now. Actually, had a shop fit the wire, as diagnosing this and installing the wire was well beyond my meager abilities.

Hi newbie here digging up an old thread! Having problems with cold starts, it's only started recently with the cold weather, first my battery was giving up the ghost so i replaced that but it's still struggling to start.

Noticed the temp gauge never seemed to warm up and the glow plug light only came on for a split second even though the temp outside was -4 so did a lot of reading on here and suspect the coolant sensor needs replacing, but decided to buy a vagcom cable because I got a few other issues I needed to look at.

Vagcom is showing fault code 17664 - Engine Coolant Temp Sensor (G62): Open or Short to Plus . So I belive it confirmed I need to replace the sensor.

Glad I found this post before I started to do any work on it! But I'm still a bit worried especially about the coolant gushing everywhere. So a few questions if any can help please?

TheGreek mentions jacking drivers side rear of car up, mines right hand drive though so I presume I got to jack passenger side up?

I like bigfish313's idea, once I have some catch device rigged up, do I hold the sensor out a little and let the coolant drain slowly? How long will it drain for, will it drain the whole system? I'm a bit confused.

Once i've refitted everything, do I just pour the caught coolant back into reservoir dont have any vacum pumps like cerickson suggests.

Sorry if this sounds a bit dumb, just new to this and want to get it right. Thanks.

great thread!

I know its an old thread but after reading through it I was able to diagnose and repair the similar issues in my car. I had a sketchy guage, low heater output and poor fuel mileage. I wanted to add results.
I bought both the CTS and thermostat and first replaced the CTS as it is a simpler fix. The tstat is currently waiting in the glovebox.
Fuel mileage went from 36 to 42 mpg. I am happy with the mpgs, the heat is better but not really hot however the guage is still erratic
Could the guage be failing or the like?

SENSOR removal...

Hey guys... It's not that difficult, IF your familiar with them, or know how they are put together... think of a fishhook..

you need to push the connector onto the sensor a bit more, then squeeze to release the clip lock properly... then it should slide right off...

I was able to remove the connector with EVERYTHING still in place on the car...

It actually looks like I might not HAVE to remove anything to change out the sensor... BUT to help my self, I will take out the intake tube for more access...


gauge is erratic, and CTS code is lighting the CEL...


J


FRUITCAKESA- you might have an air pocket somwhere...also, did you check your wiring to make sure you do not have any broken harness wires, etc??

J

I did not think about air pockets and have not checked for broken wires but the other day the CEL came on with code P0128 Coolant temp low.
I checked the CTS and it felt as if it was not fully seated.
I pulled the retaining clip, pushed on the CTS and reinstalled the clip.
I cleared the code and so far it has not returned.
I am getting ready to do the Tstat and will likely have more info after that.

This is an old but useful thread -- I thought I would add three comments. My 2004, TDI, PD, Jetta Wagon's sensor is invisible without removing anything from the engine bay -- i.e. if you don't know where it is, then you won't be able to see it. If is directly underneath something else and is completely obscured. Or maybe I have a fat head, and I couldn't get as far in to the engine compartment as some people.

Also, after you relieve pressure by removing the coolant reservoir cap, you probably want to screw it back on unless you are planning on draining the coolant as others have mentioned. Hopefully if you screw it back on, atmospheric pressure will help keep you from losing as much as I did, when I brilliantly left the cap cracked open.

I replaced my sensor to fix a CEL and CTS code, with one symptom: hard shifting. I was about to take the car to a high-tech transmission specialist, and he said that the trans used the coolant temp to figure how much pressure to apply to the valve bodies (?). No idea if this will work, but it is cheap and relatively easy to start with the CTS rather than messing with the tranny.

Very helpful pictures and comments -- thanks tdiclub!

PS one other thing -- I used a flat head screwdriver tip to push one of the legs of the plastic circlip off and to help pry the release switch on the plug. Probably a good way to break / scratch something, but I was getting nowhere with pulling on the bottom of the clip with my fingers in the very small amount of space. I was careful not to push the clip all the way off so I didn't fling it somewhere irretrievable. The tip about practicing the catch release on the MAF is a good one, as well. I still needed the screwdriver tip. I was able to complete the replacement without removing anything else from the engine bay. Hope this helps somebody!

coolant sensor change--
i read lots of help on this site.
just did a replacement myself, my suggestions..
not all sensor kits have the u-clip or o-ring
1--remove air filter box and big hose to allow easy access.
2--it was a big mistake to not have extra u-clip ready, it will likely break on removal,mine did.
3--have cool engine, remove u clip
4--slightly pull out sensor and let coolant drain into a small cup,push in sensor, pour into gallon container, repeat. maybe half gallon comes out.
5--remove sensor, you will need tough fingers or hooked seal puller to get oring out.
6--flat screwdriver got elect connector off sensor
7--pop in new sensor, connect elect harness.
8--install new u-clip or you will lose coolant.
9--install air filter and coolant refill.
10---run engine verify no leaks.

Ahhh so easy even a caveman can do it! I drained about 50 oz of coolant and lost about 20 oz on the ground. Broke the c clip that holds the CTS in place. Had to hunt for the old o ring, it was stuck inside.

First time my temp gauge has worked since it went out in 2004.

Thanks for the tips tricks and advice!

forgot to add, the retention c clip is $0.70 at the VW stealership. They have a whole bin of them in the parts dept. (Sutliff VW-Harrisburg PA)

Just wanted to post my thanks for the helpful advice in this thread. The temp gauge in my '03 Jetta just quit working this week (but no CEL codes), and I had been wanting to change out the CTS anyway so I decided to give the CTS change a shot.

I jacked up the rear driver side, and utilized the foil & funnel method posted previously. That worked great, with minimal loss and no mess. I had right at 1/2 gallon of coolant drain out, which I recovered, filtered, and returned to the system. I removed the air box but not the intake hose leading from it, initially. I tried and tried and simply could not get the electrical connector off. I decided to go ahead and remove that intake hose and come at it from directly above. That was infinitely easier, as I could get a much better angle on the connector. I wish I had just done that initially. Otherwise, it went smooth as silk, and I managed not to break the U-clip either.

All total it took me about 1.5-2 hours to get everything set up, replace the CTS, and put everything back together. Had I not had such a time with the electrical connector, it would have been about a 10 minute job from start to finish to just replace the CTS, but it ended up taking me about 20 the pull the old one and install the new one. My biggest piece of advice would be to take that intake hose out and go at it from above. That was the key for me.

Thanks

Thanks to all the posts on this thread. Replaced the fuel filter and coolant temp sensor with minimal mess and waste. Used the garbage bag trick for the CTS replacement. Runs great so far.

Coolant Leak when warm - Sensor works - ??

Hi Everyone - I read a few threads similar to my issue, but not 100% sure it was addressed so quick follow-up question to the masters.

Temp Warning light comes on when cold after first start. For a couple weeks, I could wait 5 mins, then restart car and light would remain off. Now, light stays on all the time.

Warmer day last Sat here in Seattle, driving around 65 when pull to a stop, notice white smoke coming out driver's side under hood - yet temp gauge shows a consistent 190 (has never gone higher in 6 years).

Pull over - coolant is leaking and burning off. I hear an almost hissing sound in the area of the Tstat housing manifold assembly. Further testing tonight -- warmed the car up, it finally started leaking again, turned it off. Hiss is there again, and I can alter the sound of the hiss when I pinch the hose that runs on top of the housing where the 3 GP's attach. This seems to be the ONLY hose with an extra layer of braiding. Hose is soaked, and so also is the sensor - can't tell if this hose has a leak, or if the sensor is leaking (and I change the sound when I pinch the hose).

Seems weird that it wouldn't leak until warm if it is the sensor.

Here are some pictures. Question - should I just replace the sensor now, and see if I still get the issue (leak and hiss)? If the issue remains, then go further to replace hose or ?? I guess I'm asking if I'm missing anything else simple (to you, not simple to me) - <smile>.

Thanks in advance.

Here is the hose in question:


Here is the Sensor (other side of the hose I'm holding is at the top of the pic).


Another view, slightly lower.


This pic clearly shows how it has been leaking on the hoses/etc below. Again, can't tell source, but leak seems centralized here.

temp sensor

sorry for the newbie question , but I still can't tell where the temps sensor is .. I have an 03 TDI jetta , and had a engine code triggered .. the first couple of times it turend off when I shut the car off .. the last time it stayed on , till I used a code reader to reset the code .. so i'm pretty sure the sensor is going out .. I still can't figure out what everyone is talking about and where this sensor is ... could someone circle it on this pic ?

John, the pics in the above post might give you a general idea, although the engine is a BEW. The coolant sensor is in the rear of the head on the driver's side. When I changed mine I left the wiring harness connected to the old sensor and removed it as the final step after the new one was in place. This way you can bring it up closer to disconnect and you won't lose the old sensor.

JB05 said:

John, the pics in the above post might give you a general idea, although the engine is a BEW. The coolant sensor is in the rear of the head on the driver's side. When I changed mine I left the wiring harness connected to the old sensor and removed it as the final step after the new one was in place. This way you can bring it up closer to disconnect and you won't lose the old sensor.

Click to expand...

ok, so correct me if I'm wrong , I need to look on the car and determine if the sensor is blue or green to order the right one ... than just follow the procedures on this thread...

I feel bad that's i'm such a newbie , but frankly i've put 120k on my 03 TDI and the only thing I ever had to replace was 1 glow plug ... I had the timing belt done at 100k .. the rest is all like it came new .. have not even needed brakes yet either .... the car does not shift as good as it used to either.. not sure if the manual transmission has fluid that needs to be changed too... she's getting old and probably need some TLC ... she used to get 50 mpg .. now she gets 40 ... i'm just not a mechanic .. thanks for your help !! I think this sensor won't be a big deal with all the help on this site .. I'll just take my time ..

John.

well, got the part in tonight and put it in... who ever said it would not leak coolant was mistaken, at least a quart fell out when I pullet the sensor.. and the little cup I put under overflew in a hurry!! so to the dealer tomorrow for some g12! the clip that holds the connector also broke , but it seems like a snug fit , i hope it holds... it's never easy!!

First off I'd like to say thanks to everyone who posted their experiences with replacing the sensor. It helped me a bunch.

I just finished mine up. The only snag I ran into was the old o-ring which was stuck inside. I used a small flat head to lift it a bit, and then it came out easy. I had bought a 1.5L bottle of G12 plus plus to replace the coolant I lost - which was more than enough.

Thanks for the thread!

I just did mine, took three attempts. I couldn't seem to get the clip to set correctly on the back side of the housing. I finally took the housing off and the problem was obvious. Upon taking it off I found the o-ring to be damaged and the inside of the housing had eroded to the o-ring boss so I replaced the housing too.

Pics for those that want to do it the 'little bit longer' way:

Bad part:


New part, off the car, then installed:

completed today on a 2003 Beetle TDI - Thanks for the pointers gang!

Need to keep this thread active. Completed my replacement today on a 2003 Jetta TDI. Very smooth if you take the time to prepare as per many of the recommendations above.

Thanks.

I did it Paramedick's way & opened the drain, but only about half a gallon came out? So I set an old McD's cup under the sensor before a pulled it, and caught about another pint. Getting out the old O-ring was a PITA. Fuel mileage is better again, since no low temp readings.
Thanks for the advice guys!

I just replaced my coolant sensor and had to replace the connector to it. Sometime the clip that holds the connector on was broken. The Temperature gauge hardly works now. So I went through the continuity on each point in the connector to the wires in the back and there is continuity. Is there a color code wire diagram for the connectors labed in the back 1-4 ? Do I replace the connector prongs with new?

I just swapped out my sensor. The tip on pushing the sensor clip IN then pulling it out made it so easy! the hardest part of this was draining the antifreeze. It took more prep work then anything else.

Thanks again, TDIClub!

replaced sensor on the egr side of engine below the egr,still no reading of the temp from the ga.there seems to be another sensor on the back of the head,is this correct that there are two?