I recently purchased a 2006 S Type. In the past week, my low coolant light has been coming on and I seem to have a leak where the overflow hose connects to the reservoir (radiator?). I've added 50/50 blend and then it leaks from that connection, the warning light comes on. No huge problem until on my way home today. The warning light went off and the temp shot all the way up, FAST! I stopped a total of 5 times on my way home, plus twice that I turned the engine off while sitting at stoplights (the drive is less than 15 miles). When the low coolant light is on, temp is fine. Light goes off, temp shoots up. I turned my heater on high and it didn't help the temp at all. And the hose looks brand new, just possibly a loose connection (according to a guy at work who looked at it). Is this a thermostat issue?

 

it will most likely have a broken plastic nipple . its very common .
you need to refrain from driving un till the leak is fixed .
my guess is that the steam coming up through the reservoir from your boiling engine is sending the low coolant float to the top , thus putting out your light .
i've seen pic's of people drilling out the old nipple , tapping a thread and screwing in a brass hose tail ,but the best repair is a tank replacement .
i just done mine last weekend for the same reason , bar the over heat thankfully .
i was lucky it broke during removal for another job .

 

+1 on that. On my '02 V6, I've noticed the cooling system is VERY erratic if pressure can't build up as designed. With low pressure, either the coolant doesn't flow through the proper route, or steam pockets develop and cause havoc with coolant flow. Maybe it's a combination of the two, who knows. Of all the vehicles I've ever owned, this is the most finicky about the need for proper cooling system pressure.

 

Thanks! I will try that. Fingers crossed for a relatively easy/inexpensive fix!