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Go Blue!
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Discussion Starter #1
Hi everyone!

When driving to work today the blue temp/coolant light stayed on for longer than normal. Then it went to constantly flashing. This was all in the course of a 60 mile trip on the highway. Average driving speed was 65-70 mph. Outside air temp was 77 degrees and cloudy (perfect driving weather!).

I do have a ScanGuage installed and it read 190 degrees most of the trip and occasionally went up to 193 degrees and dipped to 188 degrees when I was in town traffic, then back up to 190 degrees.

I checked the coolant level and it is full, so I am assuming this must be a temp sensor malfunction??

Is this a problem that I need to worry about before I go home from work today: 60 miles back on highway roads? Or can I get it fixed/looked at at a more convenient time so long as I monitor the engine temp readings from the ScanGuage?

Also: when I started up Buglet this morning it sounded like a belt was screeching and then it stopped as soon as I turned the interior air blower on. I did not put the a/c on first thing and I always turn off the interior air when I park the car.

Thank you in advance for any advice :)

I can not make this photo turn the right way :confused:
190 degrees.jpg
 

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Go Blue!
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Discussion Starter #2
Note about the ScanGuage photo:
The "49.8AVG" reading is fuel economy, not engine temp average. Sorry if I'm stating the obvious :eek:
 

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5/23/10 <3
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Sounds like a bad coolant temp sensor to me. I wouldn't be overly worried about it though. Get it done when you can, but it shouldn't really cause any serious problems.
 

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Would also consider replacing the thermostat as well. Do not have any baseline info for the 1.9l Diesel, maybe others can chime in here.

It appears that the OE thermostat temp is supposed to be 97C or 188F?? If this is the case, then expect the coolant temp to likely run approximately 15-20F higher than the thermostat operation point. This is due to the location of the temperature sensor in relationship to the thermostat. The engine operating temperature is always higher than the thermostat rated temperature except in a very few specific cases.

Your temps should actually be slightly higher in town than on the highway, unless for some reason the Diesels have a tendency to behave differently than the gasoline engines.
 

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The TDI is almost impossible to get warm, and give cabin heat in winter, if you aren't driving it. So not surprised that the temp dropped while it was idle.
 

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I have heard comments about Winter heat issues. You are clear very far North!

Again, I have not played with a TDI motor, so do not know what the total differences are, but maybe my thermostat theory is more of an issue on the TDI motors.

Not sure if the cooling system has a large volume, the water circulation path is and issue, the engine block mass?? Maybe the Diesel is more efficient as compared to a gasoline motor?

A bit puzzled why the temp would drop in town unless the stat is weak?

You would need to get a sampling from a number of TDI owners to track the baseline behavior of these engines to see if this is normal??
 

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Go Blue!
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Discussion Starter #7
Thanks for all the comments and input!

Everything was pretty much the same on the trip home this evening: Blue Temp light flashing the whole way. My reader said 190 degrees most of the time and went up to 197 degrees on long hill climbs.

I have a call in with the TDI Guru in our area... really hoping he will call me back and that I'll not have to go to a local shop with this :)
 

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Likely you will need a coolant temperature sensor as I recall these are 4 pin sensors with both the cold light circuit and the coolant sensor for the ECU.

Then I would still watch the engine temp and consider a thermostat. Not sure how old your current stat is, but after about 3 years, most are soft, spring is weak and they open too soon.

I would expect the engine coolant temp to be 10-15F above the stat operating temp? This would put the engine in the 203-205F range which is where the gas engines run.

You obviously have a way to display the engine temp, maybe other 1.9 TDI owners can chime in with what they are seeing and at what ambient temps?
 

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Go Blue!
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Discussion Starter #9
Likely you will need a coolant temperature sensor as I recall these are 4 pin sensors with both the cold light circuit and the coolant sensor for the ECU.

Then I would still watch the engine temp and consider a thermostat. Not sure how old your current stat is, but after about 3 years, most are soft, spring is weak and they open too soon.

I would expect the engine coolant temp to be 10-15F above the stat operating temp? This would put the engine in the 203-205F range which is where the gas engines run.

You obviously have a way to display the engine temp, maybe other 1.9 TDI owners can chime in with what they are seeing and at what ambient temps?
jfoj, I can read the engine temp through a ScanGuage, the best gadget I ever bought!
I have no idea how old the current stat is, we have only had this car for a month tomorrow :)

Our local TDI Guru called a little while ago, I will drop the car off at his house tomorrow night and leave it there over the weekend as we are going out of town. He said that it can't be anything serious judging by the engine temp readings from today.

He is going to also take a look at the sensor in the coolant tank along with the the temp sensor. He said the the coolant tank sensor can also malfunction due to corrosion of the probes. Either way he will give it a good look over.

He will also be checking all filters etc and give the engine an overall check up when the car is with him. I'm hoping that he does not find anything crazy under the hood.
 

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My money is on the sensor in the bottle.

And I hope he doesn't find out what I think that means, that someone added the wrong coolant to the car at some point. The vehicle obviously still works, but doing that will cause corrosion and such.

A few months ago I was walking through the parking lot of Canadian Tire and caught a fellow just before he started pouring green coolant into his Jetta. He like many have no idea that the VW engines all use G12 and that using the wrong coolant can cause corrosion in the engine or that mixing the coolants can result in strange chemical reactions that from what I've been told turn the coolant into a jello.
 

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Go Blue!
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Discussion Starter #11
My money is on the sensor in the bottle.

And I hope he doesn't find out what I think that means, that someone added the wrong coolant to the car at some point. The vehicle obviously still works, but doing that will cause corrosion and such.

A few months ago I was walking through the parking lot of Canadian Tire and caught a fellow just before he started pouring green coolant into his Jetta. He like many have no idea that the VW engines all use G12 and that using the wrong coolant can cause corrosion in the engine or that mixing the coolants can result in strange chemical reactions that from what I've been told turn the coolant into a jello.
I have no idea what coolant is in there right now, it has an orange/pink tint to it, definitely not green. The fill level looked very full, above the line, but I did check it while the engine was still hot and it was probably expanded!?!

Good for you for stopping the guy from adding the wrong coolant, what a nice thing to do for somebody :)

I'll keep this thread updated when we find anything out. Although that might not be until after the weekend.
 

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Worry less, drive more
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The TDI is almost impossible to get warm, and give cabin heat in winter, if you aren't driving it. So not surprised that the temp dropped while it was idle.
You're much farther north than me but I have never noticed this issue even in temps below 0. 5 minutes or so of driving and it's warmed up and toasty. My TDI also holds heat at idle better than my mom's Mitsubishi. I used to use the heated seat until it got warmed up but the elements burned out. :(

to the OP - it's best to check and add coolant when the engine is cold. "The level should be at the max mark with the engine at operating temp and between the min and max marks when cold." Bentley manual, get yourself one because it's very nice to have to refer to even if you don't do the work yourself
 

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Go Blue!
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Discussion Starter #13 (Edited)
I took a look at the coolant sensor probes this morning and from what I can tell they do not appear to have corrosion on them: keep in mind I only viewed them from the opening in the coolant tank and did not remove the sensor.
I took a few photos but it is not easy to get a good angle in that location.
Coolant sensor probes.jpg

The coolant looks way over filled according to the manual and the fill lines on the tank, I have no idea if over filling would cause problems or not.

Coolant fill level in manual.jpg
 

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It was filled to there and the engine was cold?

That might be the issue, or a symptom at least. So not the wrong coolant but maybe over filled the coolant.

I did my coolant last year and as I recall the instructions were to fill to the Minimum line while cold only. I think that applies to most liquids that expand when heated. Power Steering is this way too, min while cold max while hot.

You're much farther north than me but I have never noticed this issue even in temps below 0. 5 minutes or so of driving and it's warmed up and toasty.
I have a 50 minute drive to work each day as I live outside the city here, in January my engine temp light takes 10 minutes to go off while driving on the highway, the cabin is warmish by the time I get to the city limits in 25 minutes, and it is hot about 5 minutes before I get to the office. So I start in gloves, hat, and coat done up fully, and end steaming it up with my coat open and hat thrown off.
 

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I've filled my coolant bottle to max when cold and have no problems. I bet you just need to replace your coolant temp sensor.
 

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Temp sensor and thermostat. Be careful about what thermostat you purchase as I see many lower temp thermostats available for these engines. Suggest getting an OE stat from an online dealer.

1stvwparts.com or some other online source would be an option.
 

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Go Blue!
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Discussion Starter #17
Temp sensor and thermostat. Be careful about what thermostat you purchase as I see many lower temp thermostats available for these engines. Suggest getting an OE stat from an online dealer.

1stvwparts.com or some other online source would be an option.
A TDI mechanic has the car for the weekend, he will check the coolant sensor, the thermostat and the coolant temp sensor. It was my first time meeting the mechanic: what a lovely man and very passionate and knowledgable about TDI engines. He has a really nice looking Jetta TDI parked outside his house with 225K miles on the clock. So Buglet is in good company, both car and human, this weekend :)

Thank you all for your input and advice. I'll report back after the weekend and as soon as I know anything.
 

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Easy fix the bf just completed on my 01 tdi. You need the pink coolant and more than likely a plastic clip for that hose you have to take off depending on age of yours. Mine did same thing blinking blue, stays on long time goes off comes back on randomly. So we did the temp sensor
 
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