Quote:
Originally Posted by 2011 Nismo#91
Just curious whats the need for being so thorough with removal of the old coolant, 3 flushes, vacuum pump, etc. Sounds just a tad excessive.
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Back when there wasn't much difference from one type of antifreeze and another, flushing was just to get rid of any solids that may have accumulated. Nowadays, coolants can be incompatible and you need to get rid of the old stuff. A triple rinse is a bit much but DI water is pretty cheap. One good flush would probably work well (depending on how much gets trapped in the system after draining); two should get rid of all of the old coolant; the third is just for good measure.
If you are using the same type of coolant, one flush to get rid of solids is all that is needed (and that may not be necessary).
The vacuum pump is to remove air from the system - you can (usually) bleed the system without one but it makes things a little easier.