Flashing Coolant Warning Light on Cold Start

Hey all,

Have a question for the forum. I have a 2002 Jetta TDI. Recently I've been getting a strange code on cold starts. I do a regular start on cold days (let the glow plug warm etc...). About 30 seconds after the vehicle starts, the Coolant/Temperature warning light chimes and then flashes. Coolant level is fine and vehicle never runs hot. If I turn the vehicle off and restart, the code always goes away and never comes back until the next cold start. Any idea what this warning may be -- read the manual and it does not indicate what the code may be so figured I'd come here as I know the dealer will tell me to bring it in for service.

normally when there is the red flashing thermometer the coolant is low.

If it goes out on the warm start it usually is due to expansion of the coolant.

Then you shut it off the coolant contracts setting off the sensor.

It would be easy enough to pour in a cup of water or coolant and water and see if that cures it.

I had a similar thing after my timing belt/water pump replacement.

If a cup of coolant doesen't do it mabee the sensor/wiring is faulty.

make shure to use the right coolant for your car.

good luck matt

My car was doing that too for the last couple of months. Every few days or so, out of the blue, the red temp light & chime would come on. I did a flush & fill of my coolant system when I did my timing belt and no warning lights since? Perhaps your coolant is old and needs a flush & fill? The sensor obviously works on conductivity and if the coolant is old enough, perhaps it no longer conducts like it should? I am no expert, just throwing out ideas?

I've been having the same problem on cold starts over the past 2 months, usually the ambient temp has to be below freezing or so. Once the engine warms up a bit the flashing light goes away. I don't think it is a function of old coolant, this stuff is supposed to go 100K before changing, and I have had 2 refills during the life of my car, the first when I had a coolant leak and the other when the engine was rebuilt. Any other ideas? So far 30K on the last change.

I had the same, VAG-COM checked out and I couldn't quite pin down the problem. Finally decided it was an intermittent or flaky temp sensor. Replaced sensor and this solved the problem. Sensor is cheap and easy (once you figure out where it is).

I just had this same problem this morning and was afraid to let it warm up. When I checked the reservoir, the coolant looked low. In Baltimore here this morning, it's really-frickin'-cold degrees, and I've never had this problem before.

The notion of expansion and contraction in cold and warm weather is plausible, I guess. Does anyone know the expansion coefficient of the G12 coolant? Is it on the bottle?

I live in Michigan and it was cold also and I had the same problem with my temp gauge. I started it up and the light came on an blinked on and off. Drove the car and it did not stop blinking so I pulled over and stopped the engine. The light did not come on and did not blink. I was also freakingout thought the engine would over heat but the temp stayed at its normal operating temp. This mourning checked the coolant level and it is a little low. Funny though after the first cold start the light has not come on. It has to be what u stated before about the expansion of the coolant. So I will make my way to the dealer and buy some coolant.

Thank's for the post
2003 jetta, slv, wagon

I had the same problem yesterday morning, but I topped off my coolant and the light went away.

Can anyone explain the difference between the pink coolant from the VW dealer and the typical green stuff you buy at the gas station? Just curious...