[HotZ28]

Not to avoid your initial question, but if you are loosing coolant, you need to find out why and fix the leak. It could be the infamous upper manifold leak and the coolant is being ingested into the engine. (Bad news) Even if the leak is external, it needs to be fixed before it runs hot while on the road and leaves you stranded. It is not a good idea to use water in the overflow tank, always use a 50-50 mix of coolant/water.

I don’t recall seeing a separate coolant light for the overflow tank, on the Buick Lesabre. Most of them do have a coolant level indicator in the radiator, to offer low coolant notification before you get low enough to cause an engine to overheat. If all leaks are stopped, there should be no need to check the overflow tank, except during routine maintenance intervals. (3-months or 3000 miles). I normally raise the hood on my car at least once a week, to check everything, regardless of whether it had a problem or not. It just makes good sense!