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Discussion Starter #1
Hey folks, Need a bit of advice here.

Today was the first real cold morning we have had this year. I scraped the wife's car (a new-to-her 2007 NB) for her and she started it up. After running about 30 seconds there was a beep, and the red coolant light on the dash started flashing. I checked the coolant and it was fine, no leaks, etc, no hose issues, the engine sounded fine. Anyway, I had her shut it off, wait about ten seconds and start it again.

This time, no light, and she drove it 40 miles to work with no issues. My question is WTH! A fluke, an impending issue, or????
I really HATE that this car does not have a temp gauge or oil pressure gauge, but she won't let me put a gauge pod in it for her.

Anyway, thanks for any help.

Glenn
 

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As the red flashing coolant light is triggered by a temperature sensor, and it was just a momentary thing, it would be an educated guess that the thermostat was stuck (or at least wasn't opening) and then released. Potentially the thermostat is failing. I suppose a failing temp sensor could cause the same thing.

M.
 

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Discussion Starter #3
Thanks MORAV,

I was leaning toward a wonky temperature sensor, but I suppose it could be the thermostat aw well. If it happens again, I might give the thermostat housing a tap or two to see if that changes anything. I'll also check the sensor connection. I was thinking of checking for codes, but since the CEL never illuminated, I doubt if that there is a code stored.

Anyway, thanks for the pointer.

Glenn
 

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As the coolant light IS the warning, there would not be a CEL or MIL simultaneously. I don't know whether or not a DTC would be stored, but if so, I don't think it would tell you anything but the overheat historical data. The temp sensor may be able to be checked with a VC, but I'm not sure about that either. Someone more atuned to the VC could answer that.

M.
 

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Discussion Starter #5
Ok, Same thing happened again today. I took a quick look at the engine, and man is it tight in there. Anyway, I have a Bentley for my TDI, but that one does not cover the 2.5 motor. Soooo, does anyone have a DIY or a link that shows not only WHERE the thermostat and temperature control sensor is at on this motor, but how to change it.

Don't get me wrong, I have wrenched on motors for the last 20+ years, so it shouldn't be too big a deal, but like I said, it is really tight in there so any tips form someone who has been there would be greatly appreciated!

Glenn
 

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Check for codes. They can throw a code even if the CEL isn't on. I had two coolant temp sensors fail. Codes both times but no CEL from them.

Troubleshoot before you go replacing parts for no reason. Why go through the trouble of replacing the thermostat if you don't need to?
 

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Glenn,

Diito SB about codes and trouble shooting. There are a number of threads that can probably help you locate the components. I'll have a look at the Bentley Repair DVD and see what is shown as to location. I don't have a 2.5L.

In the meantime, I have the Bentley diagnostics posted in this thread, not sure they are totally applicable because I understand there was a change made for the large fan from a three speed to a two speed at some point. But you might find some helpful imformation.
Bentley Cooling System Diagnostics
http://newbeetle.org/forums/2-0-liter-gas/52013-overheating-problem.html#post753256

M.
 

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Discussion Starter #8
Ok, here is the update. When the Coolant light started flashing on cold start again, I checked for codes, and there were none. I ran a scan with Vag-Com, and nothing came up either. So, based on other stories, I topped up the coolant with some G12. Seemed ok for the rest of the day, but sure enough, this morning the light came on again on the first cold start.

So this time, I pulled the plug off of the coolant bottle and jumpered the two pins with a wire. Tired it again, and NO light. Pulled the jumper off and re-connected the plug to the coolant bottle, and the light came back on again.

I'm thinking I have a bad sensor in the coolant bottle, as jumping the wires seems to solve the problem, and also if you run the car for a couple minutes after the first cold start, then shut it off and re-start a few second later, the light stays off.

Any input?

Glenn
 

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Glenn, not sure what the sensor is on the expansion tank. Can't find anything about it in either of the Bentleys. Below is where the Bentley shows the engine coolant temperature sensor. Testing of the sensor is covered on pg 19-9 of the diagnostics I posted in the link in the post above.

Perhaps there is coolant level sensor not used on the earlier models. :dunno:
.
 

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Discussion Starter #10
MORAV,

Thanks for the Bently info (I really need to get one that covers the 2007 instead of my old one from 2004)

Anyway, I was searching VW vortex (yeah, I know) for threads on the issue I have been having, and I saw several posts where someone had the same issue as I have. They jumpered the plug on the coolant bottle and it put the light out. They changed the coolant bottle and it solved the issue. Why is anyone's guess I suppose, but I assume there HAS to be some type of coolant level sensor or something in the bottle, since there is a plug/connector in it? I'm just glad I have a flashing light showing a coolant level issue (according to my owners manual) and not a solid (engine overheat) light.

Thanks again, and I will keep everyone posted on how it all pans out.

Glenn
 

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I think it must be a level sensor, but what are you seeing in the OM that I am missing. Looked at pg 84, nothing about solid or flashing, and went to pg 200, and all I'm reading is the light "lights up" if the temp is too high or the level too low. I do see a sentence "There is a fault if the warning light comes on OR flashes while the vehicles is moving, and three warnings sound"

Other than that comment, I see no reference to solid or flashing or what the independently represent.

I'm going to have a look at my '05 and see if it has these wires, got my curiosity up.

I think AutoHaus has a few used ones running on their site in eBay right now, didn't pay any attention to the year. I think I put up one of them in my "Random eBay Finds" thread yesterday, if you need that link to quickly find them.
http://newbeetle.org/forums/parts-accessories/50552-random-ebay-finds.html
Hell, I'll just look...
They do seem to be year specific, but it's stated this one MAY work
COOLANT RESERVOIR 1K0121407A VW GTI JETTA RABBIT 05-10 | eBay

Keep us posted.
 

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Okay, after reading this old thread that popped up on the board today, I'm considering tossing both the Bentleys (Service & Repair) in the trash. Not only is there an expansion tank level sensor, but a second ECT. I'm thinking a sensor for a gauge, because a temp gauge keeps showing up in Bentley wiring diagrams, leading me to believe there is a temp gauge in the TS (the OPer's vehicle in this linked post). Now to do a Bentley search for these two component numbers (nothing came up under the names). WTF? And where did this poster get all this info about resistance testing, very little of it is in the Bentleys.
http://newbeetle.org/forums/1-8-lite...emp-light.html

M.
 

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I'm having the same issue with my 2006 convertible beetle. It only does this when I start up the car in the morning and it stays on for 25 seconds or less. Seems when the temperature is under 50 it will cut on in the morning. Its most likely the sensor. So I will be at vw This weekend.
 

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coolant light

Mine is doing exactly what robertsnowdens is doing...exactly...I have same car also...but a 08...just in the morning when below 50 degresss..I have pulled off the wire to senser on over fill chamber..and light goes off and never comes on again...till the next moring...sometimes...whts up??...hmmmm
 

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Discussion Starter #15
My problem was solved by getting a new coolant recovery/overflow bottle. Turns out my sensor inside the bottle was wonky. Cost me about $30 for a new bottle, but no more problem
 
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