Best coolant flush method?

[BrianL]

Any time I've ever done a coolant flush, I put tap water back in, and although I've never had any cooling system problems, I think I'm going to switch to distilled water from now on (after reading here). But when I do a flush, I normally pull the radiator drain plug and collect the coolant, then I either do one of two methods:

1. Fill the radiator up with the hose pipe, run it, and drain it while collecting to dispose of, doing this a couple times. It's hard to have enough jugs to collect it more than a couple times, and after that it's really diluted anway, so I just let it drain to the driveway. What do you think?

2. When I did my Nissan Frontier recently, I was able to pull the drains in the block to get quite a bit more out. Since I think by then, I had drained at least 2/3 of the coolant capacity (other than what's in the heater core?), I closed the block plugs, left the radiator plug open, and just put the hose pipe in the radiator neck (letting it fill), started engine and ran until what came out of the radiator plug was perfectly clear (which didn't take long as I think by then it was near clear to begin with), letting that fall to the driveway.

Now, if I do method 2, and drain the block drains again before filling with AF and distilled water, is there still too much tap water left in the system? If so, what I can do, which is what I'll have to do for method 1, is to do one or two final fills/runs/drains with only distilled water before adding the AF. This would prevent having to use the distilled water for several drain and fills. And I just like using the hose pipe and letting it run while draining to completely get rid of all the old coolant. Otherwise, if just draining and filling, you'll always have some old AF left in there. Should I not worry about that?

Unfortnately I think the block drains on the '87 300ZX are harder to get to (turbo), so I'll probably do method 1.

 

[Buford T. Justice]

I fear tap water. Using distilled is the way to go. I usually do #2 on my 1998 Mustang GT, but you can also remove the lower radiator hose from the engine block and get most of the coolant and water out without pulling you engine block plug.

Usually, draining the radiator and block then filling the radiator with distilled water then filling it up some more with distilled water once the thermostat opens and letting run for about 15-30 minutes then draining both the radiator and engine block again requires about 5-10 times of doing this. It takes patience but it is well worth it knowing you did the job right.

 

[Ray H]

For once I actually agree with B.T.!

 

[jmacmaster]

I also agree. But if you use Buford's method, 5 drain cycles should be more than enough, since you drain both the block and the radiator with each cycle. Five cycles should be enough even if you only drain the bottom of the radiator each fill/heat up/drain cycle. In either case, I'd use distilled water for each cycle and for the final fill.

If you flush with a hose through both the block (with the block plugs out or lower radiator hose disconnected) and through the radiator, I don't think much tap water will be left after the drain and I'd just fill up with a distilled water/antifreeze mixture.

 

[Chris Meutsch]

I have a mechanical question.......if you take off the bottom hose and drain most of the engine's liquid, won't the water pump cavitate without anything to pump until the thermostat opens up? This seems like a problem to me. But, Honda says to drain the block and radiator at the same time and refill.

 

[ConfederateTyrant]

When I flushed my car, I just removed the upper radiator hose and took my old lower radiator hose (I replaced it before flushing) and attached it at the thermostat housing, then ran it off into a 5 gallon bucket. I let the engine idle and kept adding water to the reservoir until the 5 gallon bucket was just above the 5 gallon mark, then I drained it via the radiator drain valve. After that I just added enough antifreeze to get a 50/50 mixture. I don't have a block drain.

Now when I replaced my lower radiator hose I did get an air pocket which would never let the thermostat open, so my car was idling rather hot (at the top end of the normal line but never went above it). A fried of mine brought over his pressure checker and we pressurized the fluid from the reservoir into the hose to displace the air, then removed it and the temperature dropped to mid normal. It was suggested to me to fill up the radiator via the upper radiator hose and pour just a little bit down the thermostat housing just so there would be something to pump, which should have been able to purge fluid, along with the air, through the system.

 

[Buford T. Justice]

quote:

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Originally posted by Ray H:
For once I actually agree with B.T.!

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We've disagreed? Never... LOL!

 

[BrianL]

Ah, I wish I could still edit my msg to make it more clear. That stinks.


So removing the block drains doesn't remove any more than the lower rad. hose?


Buford T. Justice:
You're saying you only drain it twice?


jmacmaster:
Draining and filling 5 times with distilled water would take how many gallons? Distilled water is about $.68/gallon at Wal Mart.

If, as you think, there isn't much tap water left after draining the radiator and block, it seems it's be OK and maybe a good idea, as I mentioned above, to flush with a hose, then drain and fill once or twice with distilled water only, then drain & fill with it and AF.

How much is left in the heater core, etc after draining the block and radiator?

 

[1sttruck]

I buy twice as much coolant as I need, drain, fill with fresh 50/50 distilled water and coolant, run the engine awhile, drain, and fill with fresh 50/50 distilled water and coolant.

 

[Buford T. Justice]

I drain both the radiator and engine block (either by removing the engine block drain plug or lower radiator hose or both) until everything drains clear. Then I do both one more time just to be sure. Lastly, I drain only the radiator before I fill it with straight coolant.

 

[pzev]

Is it completely necessary to always go with a 50/50 mix of coolant to water? What about 40/60, or 30/70 coolant to water?

My car never leaves southern Cali, and is all aluminum under the hood.

 

[Ray H]

Freeze-up protection is of limited need in most areas of southern California. Corrosion protection is always necessary. I personally make a point of maintaining at least 50% antifreeze concentration in my car's cooling system.

 

[wileyE]

I look up the coolant system capacity and make sure I get 50% antifreeze poured back in, then add the water. This is to make sure that any straight water trapped from the flush (always seems to be plenty) is treated.

 

[Vilan]

If you use a little more water than 50/50, it should cool a bit better, since the water is what's doing most of the heat transfer. The coolant just gives temperature/corrosion protection. Just don't go crazy with it.

I misjudged when I refilled my radiator a few months ago. I think it's about 35/65 coolant/water. No problems so far, and from the charts I've seen it's good down to 0 F which is plenty good for me, even in winter.

 

[Steelers]

I drain and fill the radiator every 10K. This is where the convienence of this premix stuff comes in. My car takes one gallon, my truck two. Even if the system is older or never changed I would consider doing a series of drain and fills much like on a transmission. I used to spent half the day sticking hoses in the radiator or buying these silly flush kits, not worth it IMHO. Lose the old coolant, add some fresh coolant, drive it for a week or two and repeat if necessary.

 

[Louie's gone fishing]

I drain my radiator every 15k and put back a 50/50 mix with distilled water, rather than wait a couple of years and do a flush. I don't even try to get it all, just drain what ever comes out and refill.


I was wondering about a coolant filter, like one of those screens you put in the upper radiator hose?

 

[oil pan 4]

I use a regular filter.
I hooked a standard oil filter head with an oil filter to the heater hose line.
My coolant is perfectly clean all the time.
I had changed my coolant a year ago. I installed the filter. The first filter cloged with in what seemed like seconds. I pulled the discharge hose off the filter and there was only a slow drip.
I changed it and it still flows good.
Screens suck, didn't waste my time with them.
Got the idea for mine after I saw a Stock up graded kit for ford power strokes that didn't come with the filter. The one I saw was $70.
I made mine for less then $25. It works. I like it.
I don't plan on changing my coolant for a very long time with the filter on there.

 

[insomniac]

When some of you say you remove the radiator drain plug and lower hose and let all the fluid drain out, you mean with the engine running, right?

Someone brought up the issue of damaging the water pump cause it will be running dry at some point.

 

[Hawkeye74]

Here's a question that hasn't been addressed yet. How do you dispose of the old coolant?

 

[Chris Meutsch]

Flush it down the toilet.
I changed my '01 Honda over to PEAK Global lifetime (OAT) yesterday. Zero corrosion after 80k it appeared.