[kathyricks]

I have never seen "sediment buildup" in any Toyota cooling system that has always been filled with Toyota coolant. This includes 100% cast iron engines, iron block and aluminum head engines and 100% aluminum engines. I drained the coolant into clear plastic tubs and it has always been clear, not cloudy, and no "sediment" has settled to the bottom.

I own two 34 year old Toyotas that still have their factory original upper radiator hoses and hose clamps. The hoses have "1974" engraved on them. One even has the factory original metric spec heater hoses which I replaced last week only as a preventive measure. Factory radiator and heater hoses are ultra durable and metric spec for a precise fit.

My position on auto parts store hoses is exactly the opposite: they need replacing every 3 years like the Gates Rubber company suggests because they are such poor quality and not built to precise fitting metric specs. I had a 4 year old auto parts store heater hose (the the former owner installed) crack and spew two quarts of coolant into a supermarket parking lot a couple months ago. Very embarrassing.

Lessons learned: Don't replace the factory hoses until they are at least 15 years old (YSPERT agrees with me on this point too) and don't replace them with auto parts store hoses unless you expect to sell the car within 3-4 years.

What hasn't been mentioned is that the coolant hoses most likely to fail first on a Toyota are the very small diameter coolant hoses that are connected to the throttle body and often hard to see unless you are underneath the engine looking upward. These hoses may develop seepage leaks at between 10-15 years and may rupture violently when 15-25 years old. So if your car has unexplained slow loss of coolant, but no coolant dripping on the ground one of the first suspects is a seepage leak from a ver small diameter coolant hose connected to the throttle body.