The water pump is still shiny & clean, so I can't imagine why there's THIS MUCH rust in the coolant.

I found out it's low because 1) the upper hose to t'stat neck clamp was loose & the hose is swelling there, 2) the cap holds 0PSI, 3) the timing cover gasket is shot, and 4) the intake gaskets aren't much better. So the PO was topping up with plain water for over a year.

. . .

For more info, read this article that fully explains the cooling system.

Owner caption September 2014 · Photo 128 of 434