Is it critical to change coolant at 100K?

[RMcG]

Originally Posted by johnwk

I would drive the car for a few miles, until it's warmed up, with the heat on full blast.

Thanks John. But why is it necessary to put the heat on full blast?

R.

[johnwk]

Originally Posted by RMcG

why is it necessary to put the heat on full blast?

Having the heat on will make the water flow through the heater core, further rinsing out the old coolant. If the system is properly filled, the heat will stay hot through your ride. If it cools off, there's unwanted air in the system.

PS. In my experience, it takes quite a lot of "burping" the upper and lower hoses to get all the air out while filling the system. Squeeze them each slowly and repeatedly until you don't see any more bubbles at the radiator neck. And over the next week or two, double-check the levels at the radiator neck and the overflow tank. If there was air in the system that escaped, you'll need to top off the coolant.