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Need information on back flushing coolant system and re-fresh anti freeze on my 1999 DeVille Northstar

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I am a new forum member.

I need information on back flushing coolant system and re-freshing anti freeze in my 1999 DeVille Northstar.

I would like to use the top heater hose at the heater core and install a back flush tee and use a garden hose to flush until clear water runs through. Does anyone have suggestions or reasons why this will not be advisable?

Thank you for any response.



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Unless the system is clogged, there is no need to flush it - a simple drain and refill with Dexcool mixed 50/50 with distilled water will do the job. You will not be able to remove all the coolant when draining it as there are no drain plugs on the block. Introducing water into the system will prevent you from reacing a 50% concentration when refilling the system as there will be more than half the system capacity of coolant remaining in the cooling system.

With this in mind, I drain and refill mine every 2-1/2 years. You could also drive the car for a few weeks and then repeat the drain and refill process again to get most of the old coolant out.

'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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The reason you don't want to flush it is because tap water has minerals in it that you will not be able to remove, PLUS, you will not be able to get the tap water out of the block and you will have difficulty getting back to a 50/50 mix of coolant to water. Do as KHE recommends, drain and refill with 50/50 coolant to distilled water

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