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Discussion Starter #1
Some background on my temperature light issue...

About 6 weeks ago, my temp light started coming on (steady blue) in a peculiar pattern that wasn't normal. It would follow a pattern over a period of about 20 minutes where it would come on steady blue, go off for a few minutes, come back on, go off, come back on, and then start flashing. No beep. The pattern of this blue light display was very regular, almost to where I could predict when the light would start flashing as I drove by the same point on my daily commute. But sometimes I wouldn't see the blue light display at all, even when driving longer distances. It seemed to come and go.

I figured something was wrong with a sensor, and since I intended to get a new car soon, I didn't really trouble myself with it.

Today, the same pattern happened as usual, except at the time when the flashing blue usually happened, I got a flashing red and a beep. I was almost home so I didn't pull over (and the red light went off, only to come back on again about 5 minutes later, also with beep).

I haven't been able to check the coolant level yet (it's dark and snowing out), but if I should check it and it is OK, what else could be going on here? I *thought* I might have heard a sound like a somewhat sick fan under the hood, but can't be sure.

Good thing I have a new car ordered, but I still have a few weeks remaining with this one :-( What should I be looking at if the coolant level turns out to be OK when I check it tomorrow morning?

And what could the blue-blue-flashing blue pattern have to do with this now? (I realize I probably should have gotten it checked out, but, well, I didn't.)

It's an '01 NB.
 

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5/23/10 <3
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If your coolant is good, then I'd replace the coolant temp sensor.
 

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Discussion Starter #3
Thanks. So, there ARE occasions when you'd get a flashing RED temp light and a beep, if you had a bad sensor, and not just low coolant?

Because the manual really isn't clear on that. The manual implies that a flashing red light always means low coolant. (There is also something in the manual about the radiator fan, but it doesn't say much.)

I basically just need to keep this car going back and forth to the park-and-ride (2 minutes from home) until my new car arrives :) I really can't afford to take it in for service at this point. I know replacing a sensor is not expensive or difficult, but it's the dead of winter here and I haven't the time or place to go replacing the sensor.
 

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Discussion Starter #4
An update on this. The coolant was low - at the min line. I had had this low-coolant problem a year ago, and the VW repair told me I had a flange leak. Which was fixed, supposedly.

So over the weekend I refilled the coolant reservoir with the proper mix of stuff.

I drove the car around for a bit and the flashing red temp light did not return, so I thought, OK, it was a low coolant situation, the end, I don't know what happened to the coolant but I'm getting rid of the car anyway, so no big deal...

Wrong. Today when I decided to get back in the saddle and take a 20-minute drive to work, not only did the red flashing light reappear, but it threw a check engine light as well.

The coolant level was checked again today, and there was no sign of a leak.

My question: What do I check NEXT? when it comes to a red flashing temp light?

I'm counting the days until I get my new car (sadly, not a Beetle, but not so much due to the Beetle brand but because of the extreme remoteness of the dealer from my location)... but I'd just like some insight as to what's going on here. I've never seen a good, concise guide to exactly what different things the flashing red temp light can mean. Can anyone help?
 

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5/23/10 <3
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Flashing red is low coolant. If your coolant isn't low, I'd swap out the coolant temp sensor.

Have you scanned the car for codes, since you got a CEL?
 

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make sure that your cooling fans are running. My '98 beetle had something wrong where the cooling fans would not run without the ac being on, if you turned the ac off, after a few minutes you would end up with the flashing red light and beep.
 

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Discussion Starter #7 (Edited)
It's been a while since I posted here because I'm in a strange limbo situation where I'm waiting to trade this car in (waiting for a new car order). I have been driving the car minimally in the interim (less than 5 minute trips). I'm really in a bind here because I am unwilling to do another expensive repair job on this car, but now that that damned CEL has shown up, I can't exactly take it in for trade like that.

I had the code read today - it was unsurprising - P0117 - Engine coolant temperature sensor circuit low input. Also, I was alarmed to see that I'm losing coolant again, although it was not near the min this time when I checked. Having barely driven the car, I'm STILL confused as to what's going on. Is my engine running too warm, and coolant is evaporating - even on these brief hops? Or do I have an actual slow coolant leak? The car has basically been sitting doing almost nothing for three weeks.

If the car was actually overheating, wouldn't I get a STEADY red temp light? I've seen, felt no actual signs of major overheating. (I haven't been... just a flashing light after 20 minutes driving - and it flashes even if the coolant level is OK.) Today, when I drove it around on errands, I got no temp lights at all.

I'd like to get this code cleared if possible... Autozone won't do it, but would an ordinary repair shop do it for me? Basically, the ONLY journey this car has remaining to make, is a 25-minute drive to the dealer. Which doesn't even have to be done in all one chunk, so I'm not worried about the car dying on the way over there.

Need advice.
 

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Well, it could be the "Green" Coolant Sensor that you need to replace which isn't that much and takes 2 minutes to do or the sensor on your Expansion Tank is bad and you just need to replace the Tank which includes the sensor. A very common issue with older Beetle's.

http://www.ecstuning.com/Volkswagen-New_Beetle--1.8T/Search/Coolant_Sensor/ES264174/

Volkswagen New Beetle 1.8T > Search > Expansion Tank > ES#1894532 Coolant Expansion Tank - 1C0121407F

A new Cap for the tank might not be a bad idea since if it doesn't seal properly it could leak slightly and it won't pressurize the system properly.

Volkswagen New Beetle 1.8T > Search > Expansion Tank > ES#1692 Expansion Tank Cap - 1J0121321B

Replacing the above items should clear the codes. You can also unhook your battery and touch the two cables together for a few seconds that should reset your ECM and clear any codes.

How many miles are on your car and when is the last time your timing belt/water pump has been replaced?

Personally, I wouldn't trade in the Beetle. The dealer may give you some incredible amount on paper but in reality it isn't really as much as you may think. I would sell the Beetle right out and negotiate a better price with the dealer on your new car. What car are you getting?

Good Luck!

PS: Coolant doesn't evaporate. It is designed to run at high temperature so if your are loosing coolant than there is a leak somewhere.
 

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5/23/10 <3
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Also the dealer can look for codes and see if readiness isn't set (which happens when you clear out codes). They WILL know if you just reset the codes to get the car there and may not take the car or give you less money for it. Be careful with resetting the light without fixing the problem.

The temp sensor is all of $30, even at the dealer. Just fix it. It will take no time or money to do.
 

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Also the dealer can look for codes and see if readiness isn't set (which happens when you clear out codes). They WILL know if you just reset the codes to get the car there and may not take the car or give you less money for it. Be careful with resetting the light without fixing the problem.

The temp sensor is all of $30, even at the dealer. Just fix it. It will take no time or money to do.
My dealer here in Indy wants $49.95 for that Precious Coolant Sensor. And for another 100 bucks they even install it for ya :D Totally crazy for a 10 dollar part that takes 2 minutes to install.
 

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Discussion Starter #11
I'm sorry, but I don't have any experience installing parts and I'd probably just do it wrong. I also don't think I have time to wait for the part to get sent to me, either. I have no place to even look at the car in daylight except on weekends.

Why does everyone think it's just the sensor? I'm losing coolant - what does that mean? It seems like it's a far more expensive problem than just a sensor.
 

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You never did answer the question of how many miles on the car and if the timing belt/water pump has been replaced.

Noticing any puddles on the ground or coolant on anything in the engine bay?
 

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I'm sorry, but I don't have any experience installing parts and I'd probably just do it wrong. I also don't think I have time to wait for the part to get sent to me, either. I have no place to even look at the car in daylight except on weekends.

Why does everyone think it's just the sensor? I'm losing coolant - what does that mean? It seems like it's a far more expensive problem than just a sensor.
It could be more than just the sensor. Without looking at the car there is no way to tell. You have to be more specific. You could be loosing coolant from the overflow bottle if it is cracked or the cap isn't sealing properly. Or it could be as serious as the water pump going out and leaking from the shaft. If you have the Timing belt and waterpump service done by the dealer it will cost you between 1100 -1600 Dollars. You can take it to a reliable independent Euro type shop which will charge you between 450-750. A heck of a lot less than the dealer. The coolant sensor is rediculously easy to change. If you can change the toilet paper on the toilet roll you can change your coolant sensor in about 2 to 5 minutes. Unhook, unclip, remove and reverse. Simple. No special tools required. Actually no tools are needed whatsoever.
 

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Or it could be a bad computer in the dash triggering false warnings. If your coolant level is normal in the bottle and you have no puddles on the ground then it could be this.

I have been battling almost the same thing for years. Mine will come on, flash red and ding, continue doing it for 30sec to 5 mins then go off. Then a few mins later it happens again. No pattern but all random. It will do it when the car is warm or within 30 seconds after starting it (when it's been sitting for 9 hours in 20 degree weather). I even hooked a computer to the car while I was driving and got the temp reading directly from the OBD computer. Nothing abnormal, temp was good but the light still came on and flashed red.

Talked to the svc mgr at a dealership. He was confused as all temp sensors had been replaced and said there is a 2nd computer behind the dash to control the instrument cluster. That computer could be bad. Could be the same thing with yours.
 

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Or it could be a bad computer in the dash triggering false warnings. If your coolant level is normal in the bottle and you have no puddles on the ground then it could be this.

I have been battling almost the same thing for years. Mine will come on, flash red and ding, continue doing it for 30sec to 5 mins then go off. Then a few mins later it happens again. No pattern but all random. It will do it when the car is warm or within 30 seconds after starting it (when it's been sitting for 9 hours in 20 degree weather). I even hooked a computer to the car while I was driving and got the temp reading directly from the OBD computer. Nothing abnormal, temp was good but the light still came on and flashed red.

Talked to the svc mgr at a dealership. He was confused as all temp sensors had been replaced and said there is a 2nd computer behind the dash to control the instrument cluster. That computer could be bad. Could be the same thing with yours.
Very, very unlikely that it is the 2nd computer behind the dash since there is only one. :D And yes, it is under the dash on the drivers side ;)

I think your problem is this:

Volkswagen New Beetle 1.8T > Search > Expansion Tank > ES#1894532 Coolant Expansion Tank - 1C0121407F

It's the Reservoir Tank which has a built in sensor which has a high probability of going bad over time. Lots of people that changed the regular coolant sensor have found this to be their problem. Install a new Coolant tank with built in sensor and I bet your light issue will go away.
 

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Very, very unlikely that it is the 2nd computer behind the dash since there is only one. :D And yes, it is under the dash on the drivers side ;)

I think your problem is this:

Volkswagen New Beetle 1.8T > Search > Expansion Tank > ES#1894532 Coolant Expansion Tank - 1C0121407F

It's the Reservoir Tank which has a built in sensor which has a high probability of going bad over time. Lots of people that changed the regular coolant sensor have found this to be their problem. Install a new Coolant tank with built in sensor and I bet your light issue will go away.
The expansion tank was changed by the dealer. Temp sensor in line changed as well. Spoke w/ the head of the service dept and in the bug, the temp light is a multi-function light. Off of each sensor is 2 wires, one which goes to the computer and one which goes to the instrument cluster. The module (computer) which controls the temp light is currently suggested to be bad as everything else which senses or could send a signal has been replaced.

I'm as stumped on this as I can be. But all the sensors and expansion tank has been changed. And the coolant level is at the FULL/MAX line.

Right now it's just an annoyance as I know the car isn't overheating. It will alarm when the coolant temp is at 112deg, 180deg or 32deg.
 

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The expansion tank was changed by the dealer. Temp sensor in line changed as well. Spoke w/ the head of the service dept and in the bug, the temp light is a multi-function light. Off of each sensor is 2 wires, one which goes to the computer and one which goes to the instrument cluster. The module (computer) which controls the temp light is currently suggested to be bad as everything else which senses or could send a signal has been replaced.

I'm as stumped on this as I can be. But all the sensors and expansion tank has been changed. And the coolant level is at the FULL/MAX line.

Right now it's just an annoyance as I know the car isn't overheating. It will alarm when the coolant temp is at 112deg, 180deg or 32deg.
I know it can be very frustrating to track these annoying bugs down. Keep in mind that even "New" Sensors can be bad. Did you test the sensor on the New Expansion Bottle? Also did they change the cap when they put in the new Reservoir Tank?
 

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Discussion Starter #18 (Edited)
The car has 58,000 miles and to my knowledge the timing belt/water pump has never been replaced.

My dilemma is this: My new car is coming in a few weeks. This car is supposed to be a trade-in. Bad luck is that this started while I was waiting for my new car to be delivered. I guess I really DON'T want to know what's wrong with it, if you get my drift, as long as it can make the 25 minute drive to the dealer. Which it can if I nurse it. I have another car to drive in the meantime, so that's not the problem here.

What can I do to make the CEL go away? I am getting suggestions to change both the engine temp sensor and the reservoir tank (w/sensor). I could do that because the parts are affordable and I'm sure the local shop (ie not the dealer) could do these things for me fairly cheap, if I can't. I'm just looking for the most conservative "course of treatment" that I can do - doing my due diligence in good faith - without dropping $2000 or whatever.

It may so happen that I have to bring it in to the dealer with a CEL still on there and then take the hit with the trade-in value, but I'd like to see what I can do to salvage this situation.

I guess I'll rush order those two parts (the sensor and the tank) and then get the sensor replaced, then the tank replaced if the sensor doesn't clear the CEL. I figure, if I get the CEL cleared, then drive it carefully enough so the engine temp never gets warm enough to trip the flashing lights and CEL. I don't know what else I can do here.

What are the part numbers of the two items in question? Can anyone direct me to that information?
 

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Just look up on my post #8. There are the links to the parts in question. If you order them from ECS tuning it will take about 3-5 days to arrive. Those items may clear your CEL or they may not. You have really low miles on that car for a 2001 but age is another story. The Original water pump has a Plastic Impellar which has known to fail and it could be the cause of your problem. Whoever gets this car next will definitely need to get the timing belt and water pump and tensioner replaced ASAP.
 
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