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i changed the coolant in my 2003 deville today by removing the rad drain plug and got about a gallon out of it and refilled it, ran it up to temp again and pulled the drain plug again and drained another gallon out of it, i figured i got about 2 gallons out of it or 2/3rds out of it, was the amount i drained sufficient enough for a coolant change???? or should i have gotten it all out?
 

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98 DeVille, 97 DeVille d'Elegance
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Almost impossible to get all out. You can stick exhaust from shop vac in surge tank and give it a few shots of air and some more may come out.
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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The point of a coolant change is to replenish the anti corrosive additive package. A drain and fill once every 2-3 years does that just fine. No need to completely drain it. The only way to do that is to remove the crossover manifold. No, you don't want to know what that entails.....
 

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1998 Seville STS, 2003 Deville
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282 Posts
Every 6 months or so I suck out what's in the expansion tank and replace it with new.
 

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White Diamond '03 DHS (with DTS floor shift)
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You won't accomplish much. What's in the surge tank does not circulate through the system. I just kind of sits there. The level rises and lowers depending on RPM, but that's about it. That's the exact reason why, when the sealant tabs where recommended, they where to be put in a radiator hose.

If you really want to use that method, you need to drain it from the drain plug at the bottom. Then refill from the top.
 

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1998 Seville STS, 2003 Deville
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So what happens to all the coolant from the hollow bolt bypass hose? It's constantly supplying coolant to the expansion tank and mixing with what's in there.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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The surge tank lower fitting connects to a 3/4" piping T in the heater return line. There's actually a fair amount of flow into the top/out of the bottom - the flow rate is equal to purge line flow rate.

Suppose the purge line flows a pint a minute. That's a quart in 2 minutes. At that rate the entire coolant fill - 2.5 gallons - would cycle through the tank in about 20 minutes - at idle.

samert, I do exactly the same thing - every 3 months, car and truck, I siphon out 2 quarts of 50/50 coolant and replace it with fresh. The engines each receive 2 gallons of fresh coolant in 1 year. I currently use the Prestone bright yellow "universal" long life coolant mixed with distilled water.

This is the lower connector for a 2002 Seville tank, but they all work the same in the (sealed) purge line systems - even in my F-150 4.6 engine system - Identical.

The orange juice jug shows what the "old" coolant looks like when siphoned out. Although the picture is almost 3 years old, the coolant I siphon out on 30 June will be just as clear.
 

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White Diamond '03 DHS (with DTS floor shift)
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So what happens to all the coolant from the hollow bolt bypass hose? It's constantly supplying coolant to the expansion tank and mixing with what's in there.
Ahh, I forgot about that. I guess it will circulate. The low flow is the reason for not putting the sealant tabs in there.

I stand humbly corrected.
 
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