Which is the bad sensor?

chewbacca

Veteran Member
Joined
Dec 3, 2006
Location
Iowa
TDI
2002 Jetta GLS; 2002 Golf GLS (Mrs. Chewbacca)
Hi all, a few weeks ago I put new water temp sensors in both of our TDI's. I have some flakey behavior now and wondered if anyone could direct me in how to figure out which one is bad.

Since the install, one car is taking close to 20 minutes of driving, (only a few miles on the interstate) to warm up fully. The other is doing the exact opposite, the temperature gauge is reading straight up after only a few minutes to five minutes of in town driving maybe 2 miles up the road. The car that is warming up fast is kept in a garage, but it has been 60 to 70 degrees here for a couple weeks so I didn't think much of it.

Is there a way to test to see which one if either is bad? Both threw CEL's before, but aren't now. I have since gotten a bad glow plug code on the one that is warming up fast and am experiencing some occasional bucking that may or may not be on the shift point between 2nd and 3rd. Am trouble shooting tranny for that, but it seemed like the same car did some of this before replacing temp sensor and stopped shortly after for about 2 weeks.

I realize diesels take longer to warm up, but one seems to be taking an extra long time compared to what it was doing before the sensor change. (maybe normal if my sensor was bad for a while) and the other just seems impossibly quick. How long should a TDI in mild weather take to warm up? I am running shareware for Vag Com, but am about to go full version anyway if it;s something I could use to measure/trouble shoot the sensors. Just would need to know what temps to look for in the measuring block.
 

alphaseinor

TDI Innovator, Gone but Not Forgotten
Joined
Jul 30, 2006
Location
Denton, TX
TDI
'03 Jetta TDI 780,000 miles (totaled out), 01 Audi TT 225 Quattro 230,000 Miles (runs great!), 00 Cabreetle Beetle dash, ALH & MK4 harness Swap
Not sure which one...

Down here in Dallas, when it was 50*F it would take it 10 miles of hard driving to warm up to 190 indicated. I'm sure it wasn't 190 actual, because the heat was still going up in the cabin.

honestly it does sound odd... but I would just do a scan and see how the temps go up... linear or binary...
 

chromeBuddha

Veteran Member
Joined
Jun 30, 2006
Location
Arlington, TX - DFW metroplex
TDI
2002 Golf TDI manual
Try to take some of the variables out of the comparison. Park both outside for the night, then do your test drive.

My '02 warms up in about 3 miles of city driving, ~5 minutes.

Also, are they both auto? The auto will warm up faster vs. a manual.
 
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