[giark]

I have a 2003 TDI Beetle, 83k miles. For about the last six months I get a brief alarm (blinking temp lamp and beeps) indicating the coolant is low about 60 sec after the engine is started, then not again till the next start, and not every start. That is, until about a month ago, when the alarm started happening randomly, and getting more often. It always clears itself after a short time.

The coolant isn't low, and never has been, hot or cold. It's the genuine VW stuff, and nothing else has ever been in the engine. No leaks, and no coolant in the wiring. The engine isn't over heating. No mods or major work done, just routine stuff like oil, brakes, and bulbs.

I work with two other VW owners that have the same problem (both gas Jettas >200K miles), yet I can't find any reference to the problem. Anybody have any words of wisdom? Thanks!

 

[Vent5]

First things to try are: clean the electrical plug and get the car checked for codes. If there's no codes, then go from there. Most local auto parts stores will check for code free.

When you remove the plug, also check for coolant migration. The electrical plug should not be sitting in coolant since it's separated by the plug. Some coolant tanks are defective and leak coolant.

The sensor could just be bad too but this isn't a common failure. I think the tanks are pretty cheap. Another possible problem is a bad coolant TEMP sensor. Not the level sensor at the tank but the TEMP sensor at the engine. This was a common failure item. Look at the driver side coolant flange coming off the head. Behind it is a coolant sensor. It could have a problem, of course make sure the engine is cool before touching or removing it. You might see the temp gauge move though it will set off a CEL.

 

[chittychittybangbang]

No coolant in the wiring means no coolant migration. 2nd the coolant temp sensor but I'm not sure if it'll set off the temp lamp instead of the CEL/MIL light. Try going to get it checked for codes.

There are only a few sensors in the coolant system - the coolant temp sensor, the low level sensor, sensor on the radiator "coolant fan control thermal switch" that I believe is for the radiator fan, . If it's not a wiring or other fault like corrosion on the plug, one of these sensors must be bad. My guess is the low level sensor on the reservoir. Try checking the resistance of the plug. Try cleaning them and see if it goes away.

If you do need a new expansion tank, it's only about $13, part number 1C0-121-407-E http://worldimpex.com/parts/genuine-part-expansion-tank_850722.html

 

[Vent5]

Ah, you are right, I should read better, he already said the plug is dry. In that case, what he said ^^^, bad sensor is possible or bad coolant temp? What were the codes?