I'm a Newbie but chased a similar issue for days... the light would blink and immediately register full hot. In my uneducated opinion the system is designed to show full hot when the expansion tank thinks there's not enough fluid, the gauge would literally go from normal to "overheating" within a few seconds. But it wasn't overheating, the blue cap was bad so it was more of a pressure problem. What I think the gauge was telling me was the system is saying "GIVE ME COOLANT!"

I've also learned that ambient temperature has little or nothing to do with coolant temperature levels. I presume and it seems obvious that the coolant temp will run higher under load (hills, et al) and/ or in high ambient air temps, but that doesn't mean the temp will be lower under normal load on a cool day.

My gauge also blinks many times at startup, as does the Oxygen sensor gauge. At any point that I blip the throttle, all the blinking idiot lights stop.

Yes, as David indicated, if there's any temperature in the coolant it will blow out when you open the blue expansion tank cap. I also presume if it didn't blow out that might be of greater concern, as it means the natural pressure buildup that comes with warm/hot coolant is leaking elsewhere. You have to wait until the coolant cools back down to see if you have enough coolant in the expansion tank, while also making sure your coolant level is near the Max mark on the overflow tank behind the license plate.

Happy Motoring.

On Jul 29, 2013, at 11:56 AM, David Beierl wrote:

At 01:45 PM 7/29/2013, Goetz Aust wrote: > Pressure tank appears full based on color and temperature at top . No > visible leaks on ground - its raining now. Also the temp gauge > flashes 6 or > 10 times before starting and I thought it should only flash 3times.

The gauge is spec'ed to flash for two seconds every time power is applied, and any time the blinker is triggered. However as it ages the timing capacitor gets leaky and causes it to continue longer than it should. You can make no inferences about engine situation from this.

Your symptoms don't sound like the typical gauge problem though it's not impossible. It's also conceivable it's a controller problem though again not likely.

As far as the blinking light is concerned, it blinks when it thinks the engine is overheating, period. The coolant level controller tricks the gauge by briefly applying about 35 ohms to ground on the sender line which will start the light blinking. The controller does this more often than every two seconds, so the light keeps on blinking, but the pulses are very brief so the needle doesn't change much.

If the pressure bottle is actually running normally, it will be totally full and if you loosen the cap a bit on the hot system you'll instantly get hot coolant coming around the threads. I've never been able to tell the level without taking the cap off or shining a flashlight into the side of the tank so that it glows internally, especially as the tank ages.

Yours, David