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Discussion Starter #1 (Edited)
As many of you already know, draining the radiator only empties a little over half of the engine's total capacity for anti-freeze fluid (~70%). The FSM suggests draining, 'flushing' (running the engine), and re-filling as many times as necessary for the fluid to turn clear.

In effort to be a little more rigorous, I simulated the repeated drain, 'flush' on a spreadsheet. Let me know if this makes sense, or if I am way off base. Or if this is a non-consequential waste of time.

Three drains and two flushes reduce the remaining old anti-freeze to 0.9% of total capacity. I believe that is adequate.

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Were talking about ethylene glycol, water, contaminants and rust preventative. Ethylene glycol and water never go bad. Your just trying to get the contaminants out and replace the rust preventative. If you change your coolant frequently it shouldn't be an issue. I do mine annually. I don't bother flushing - just drain all I can and replace with new.

If your worried about it then do a flush with distilled water - run it for a while - then drain. At that point by your own chart you will be down to 3.5% of the old crap - or basically nothing.

FWIW - I get over 2 gallons out. You have to let it sit for a long time - the drip will continue.
 

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Discussion Starter #3 (Edited)
......
FWIW - I get over 2 gallons out. You have to let it sit for a long time - the drip will continue.
2/2.7 = ~74.1%, 0.6% higher than what I put as drained.

I was lazy; I did not measure the fluid drained though I did allow it to drip for a very long time. Instead, I measured the amount of DI H20 I was able to pour back, and then add as the air bubbles slowly came out. My burping hand is getting sore.... So I might have underestimated the volume drained.

It sure takes a lot of coaxing (burping) to persuade the fluid to run through the heater hose.

Following advice given elsewhere by Surf and Snow, I kept the radiator cap on and fed any more DI H2O through the reservoir. I also parked it on an uphill incline, and have used ramps to make the incline steeper.
 

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Or you can pull the block drains and get out even more. The drovers side is really easy, the passenger, not so much.
 

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Discussion Starter #5
Or you can pull the block drains and get out even more. The drovers side is really easy, the passenger, not so much.
Yup, was aware of that option.

If you just pull the driver side plug, is that enough to drain another litre or two?
 

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Yes, the only thing left is the passenger side block and heater core.

I tried the passenger drain but it’s really hard to access and I was afraid I was going to strip the head. I also reinstalled the factory blue coolant so I wasn’t worried about getting every drop out.
 

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Discussion Starter #7
Were talking about ethylene glycol, water, contaminants and rust preventative. Ethylene glycol and water never go bad. Your just trying to get the contaminants out and replace the rust preventative. If you change your coolant frequently it shouldn't be an issue. I do mine annually. I don't bother flushing - just drain all I can and replace with new.
......
I thought annually was excessive. The received wisdom appears to be to drain, flush and replace every 4 or 5 years.

Then I ran across this Popular Mechanics article suggesting that the radiator fluid should be changed every 2, maybe 3 years. How to Maintain and Flush a Cooling System So Your Car Doesn’t Overheat

Should I be re-thinking AFFCIs? Anti-freeze Fluid Change Intervals. If so I will be seriously thinking about getting a vacuum refill kit.
 

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5 years is only on the initial fill for long life coolant because you can't get all the old out.
From that point even using long life it is recommended every 3 years from what I have seen.
 

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I thought annually was excessive. The received wisdom appears to be to drain, flush and replace every 4 or 5 years.

Then I ran across this Popular Mechanics article suggesting that the radiator fluid should be changed every 2, maybe 3 years. How to Maintain and Flush a Cooling System So Your Car Doesn’t Overheat

Should I be re-thinking AFFCIs? Anti-freeze Fluid Change Intervals. If so I will be seriously thinking about getting a vacuum refill kit.
Its no doubt excessive but I do all the fluids once per year now - diffs, transfer case, coolant, and trans (when I drove 40k+ miles per year I would also do a trans drain and fill at 6 months as well). It just keeps my life easy to do it all at once.
 

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I can appreciate this thread and info. Thinking to drain the green stuff and go with long life blue and they probably shouldn't be mixed.
 

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Discussion Starter #12
5 years is only on the initial fill for long life coolant because you can't get all the old out.
From that point even using long life it is recommended every 3 years from what I have seen.
Thanks. This is a little embarrassing.... but what the hell. Always better to learn late than never.

I just checked the FSM (2006). It recommends that after 96K km/60K miles or 4 years, that the coolant should be replaced every 48K km/30K miles or 2 years.

A similar replacement schedule every 2 years is recommended for our other vehicle, a 2015 Kia Soul.

I am flushing the cooling system as I prepare to remove and replace the radiator. Took it in for a flush and replace at a local Kal Tire early in 2020. It started to leak a tiny bit and then the leak became more noticeable after going over a white-knuckle trail in September. Kal Tire also refilled with green rad fluid, which in hindsight, would not have been my choice.

I cannot blame Kal Tire for the leak as the coolant had not been refreshed in 6 years......

Lessons learned:

1. Reading the manual is not enough; sometimes reading the manual CAREFULLY is critical.

2. I see much shorter coolant change intervals in the future. 3 years at the outside.

3. I see a vacuum refill kit in my future because coaxing the air out of the system is doable but tedious.
 

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Discussion Starter #14 (Edited)
I can appreciate this thread and info. Thinking to drain the green stuff and go with long life blue and they probably shouldn't be mixed.
By the third drain, the drained fluid was quite clear. Took about 6 bottles of DI H2O. 3.78 litres/4 quarts each.

I also added half a bottle of rislone Hy-per Cool Clean and Superflush after the first drain. Not sure that was really necessary.

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The Xterra will self purge all the air out as long as you keep the fill tank at the MAX mark, no need for one of the vacuum bleeders on the X.
 

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Discussion Starter #16
The Xterra will self purge all the air out as long as you keep the fill tank at the MAX mark, no need for one of the vacuum bleeders on the X.
True.

While flushing the system, I wanted fluid moving through the heater. Burping/gurgling the upper radiator hose made that happen much faster. The alternative was to run the engine, shut if off and wait overnight, preferably while parked on a slope.

Pouring anti-freeze/coolant into the radiator is a bit tedious. The vacuum refill kit should accomplish the same in far less time.
 

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True.

While flushing the system, I wanted fluid moving through the heater. Burping/gurgling the upper radiator hose made that happen much faster. The alternative was to run the engine, shut if off and wait overnight, preferably while parked on a slope.

Pouring anti-freeze/coolant into the radiator is a bit tedious. The vacuum refill kit should accomplish the same in far less time.
I agree, they are an awesome tool. I was just pointing out they are not "needed" like on some vehicles that will never purge the air out without one.
 
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