Over the weekend I took my 2000 Toyota 4Runner to a local shop to get the oil changed. While there they told me I needed to flush the coolant, pulling clear water out of the coolant reservoir. They insisted that the water in the coolant could cause problems for my engine. Also insisting that I couldn't flush it myself because it requires special equipment.
Given that I know antifreeze is in the engine and it was last serviced by the dealer I'm a little perplexed as to how water (or a clear liquid anyway) ended up in the overflow.
My guess is that coolant is low, so the overflow was empty. They added water so they could up-sell me into flushing the coolant system.
Is there any other reasonable explanation for how that could have happened?
(for the record I didn't have them flush the coolant)