Radiator flush game plan for critique

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Jul 23, 2021
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Planning a few radiator drain/flush in the coming month.

Vehicles have coolant that looks fine in some, discolored in others and all are of unknown age, possibly decade or longer. They need to be done, at least as preventative.

Just working out a game plan with some questions.
[I am amending my plan to not use hose water, the more I read the more it appears to only use distilled water due to the sediments that will remain in with any tap water.]
Add a Prestone coolant flush to help dissolve and loosen particles to remove them. Product claims to remove rust, scaling, contaminants, etc. Leave it in for a few days of driving.
I plan to drain the radiator either with a Mityvac, or failing that with the valve below.
Then plan to add water to idle the car. The question is whether free tap water or whether I need to use distilled water is important, knowing that this will be flushed out momentarily. My tap water does leave white sedimentation.
Next step, with just water, idle the car with the heater on for 5-10 minutes.
Drain this. Maybe repeat.
Refill with 50/50 coolant of appropriate type, antifreeze + distilled water.
Run the car to burp the air out of the system.
Check levels and refill.
Dispose of old coolant/water at the local auto shop or county recycling.

Am I missing anything, and do you have advice on free hose water vs. distilled bottled water at a buck per gallon?
 
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JC1

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How bad is the condition of the current coolant? When I drained my civic 2 years ago, I did it in summer. Drained coolant in rad, then topped up with tap water. Ran that for a while. Drained and again added more tap water. Ran that for a few more days. Car is my wife's short tripper usually.

Then I drained that and I also removed the thermostat and shop vac'd the water in the block as much as I could. Then refilled it with distilled water first for another flush. Once I drained that, I refilled with 50/50 coolant and distilled water. Ran it until it circulated and topped it up. I made sure to use the heater to get the heater core flushed out as well during this process.

The car has had regular coolant changes in the 23 years I've owned it. Only flush I did was some purple power in the coolant reservoir. I changed the thermostat for the first time as well as part of the maintenance.
 
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I'm a semi mechanic. We have a company called Crystal Clean which deals with our used coolant and disposing of it isn't free. Don't bother a garage with your old coolant. I use to flush my old coolant down the toilet when I had city water & sewer.
 
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About half your flush water wont come out the drain so if you use the prestone you may want to run several flushes making sure the thermostat opens each time. Then you need to fill with 100% antifreeze and after running to mix everything, check the coolant % with a tester and adjust as needed. If you use tap for the flush you wont get it all out just like you wont get all the coolant out. 1 flush 50%, 2 25%, 3 12.5% and so on, but check you manual for coolant volume and measure what drains incase you get more or less than 50%.
 
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Unless it's a really old vehicle like 20+ years or if the coolant is in really bad shape than a coolant flush is generally not needed. Almost all OEM's now just recommend a simple radiator drain and fill for a coolant change.
 

CharlesInCharge

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Unless it's a really old vehicle like 20+ years or if the coolant is in really bad shape than a coolant flush is generally not needed. Almost all OEM's now just recommend a simple radiator drain and fill for a coolant change.

Well it's already in the radiator. The cost was $4 for a bottle from Walmart. And my vehicles tend to be about 15 years old on average.

The Mityvac sucked out about 6 liters, or roughly 1/2 of the entire capacity, topside so no need to crawl under or risk damaging the drain plug or making a mess on the ground. 20 pumps and the fluid was out in 5-10 minutes. Prestone says to add the 22 oz bottle and fill with distilled water so I followed the instructions.

Next is to drive it for a few days, run the heater, and drain and fill with distilled water. And repeat that flush and fill until it seems that all I'm getting is clean water, idling with the heater between drain and fills. Should not be too difficult and probably under $35 in materials when done. $4 for the flush, $20 for the antifreeze, and probably $5 for all the water. Oh, and another $5 for a new thermostat. This is an example of how DIY saves a lot of money, since shops tend to charge around $100 for this service, maybe more.

I have the drained coolant and it looks okay. I'll be very curious to see if the flush does its job and pulls out a lot of sedimentation.
 
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Virginia
I just did a 22 year old - thoroughly.
I think the best thing you can do is remove the stat for a while. Then all your running will be 'churning' water around. You can use your winter radiator shield to cut cooling air if you want.
I also think the cheapness, thoroughness, velocity, and willingness to do it one more time of 'free' hose water for the actual flushing makes a lot of sense.
Then, next to last, dilute that last hose water flush down with the distilled water. (Now probably, what, 10% or less?) Run that to churn a bit, drain and start real filling. (Now maybe 1% hose water? 10% left of 10% water, etc...)
My system had a very low radiator drain, an old school cap, and 1 easy to get to heater hose connection - so I used each on each cycle. (I didn't want to risk block drain troubles...)

Based on a lot of reading...

I did:
Stat out,
Drain, rinse, drain, cascade run to hot twice, soak between,
Drain, rinse, drain, shout run to hot twice, soak between,
Drain, rinse, drain, shout run to hot twice, soak between,
Drain, rinse X10, drain, distilled fill and run,
Drain, filled with final products.

My final fill was 1/2 gallon NAPA green full strength, twice (1/2 of 2 jugs), then I could fill those with 1/2 gallon of distilled
each (other 2 1/2s distilled into radiator) and know they were mixed right for topping off burps and carrying for later. Total was 4 gals distilled (2 flush, 2 mix), 2 coolant. I got a good gallon of mix for traveling. JIC

I also worked my overflow tank separately as I warmed up the first time. I was not satisfied (correctly) with siphon emptying and drug the shop vac (reversed) out to blow clear a couple of times.
 
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Joined
Apr 12, 2021
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- The incessant talk about the detriment of using a garden hose is laughable. People speak as if there will be instantaneous calcium and lime buildup. Pure BS. Been doing low-pressure flushes on my cars for 30+ years, and you could eat off the inside of any of my cooling systems. But go right ahead and buy 20 gallons of distilled water for 20 bucks...

- Proper draining - to include removing block drain plug(s) - will enable you to get most of the flush water out. For the heater core and rear heater units, a shop vac reversed to "blow" works great to get residual water out. Don't know why folks insist upon keeping water in their systems when they can get it out. Are the drain plugs a pain to get to? Sometimes. Are you going to get wet? Probably. Do the job halfway and you'll always get half of a result

- Skyactiv is correct with regard to disposal. Check with your city, but if on municipal water most places will tell you to "flush it"
 
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I have really hard well water. I have rinsed my radiators out with the hose and refilled with distilled and coolant, radiators looked fine.
 
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- The incessant talk about the detriment of using a garden hose is laughable. People speak as if there will be instantaneous calcium and lime buildup. Pure BS. Been doing low-pressure flushes on my cars for 30+ years, and you could eat off the inside of any of my cooling systems. But go right ahead and buy 20 gallons of distilled water for 20 bucks...
You just joined in April and it's already "incessant"?
 
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Most cars have coolant going through the heater core 100% of the time. So turning on the heater only slows down the heating up of the coolant and cycling of the thermostat.
 
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Where I'm from the well water is called "liquid rock". How it dries and the quantum of what it leaves is astounding.

Friend's laughed at my use of distilled in my coolant jobs. They used the well water.
Their coolant reservoirs took less than a week to turn cloudy where mine stay clear enough for a magazine ad.

$20 for the cherry on the hard earned sundae? I'll take it.
 
Joined
Jun 28, 2003
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Where I'm from the well water is called "liquid rock". How it dries and the quantum of what it leaves is astounding.

Friend's laughed at my use of distilled in my coolant jobs. They used the well water.
Their coolant reservoirs took less than a week to turn cloudy where mine stay clear enough for a magazine ad.

$20 for the cherry on the hard earned sundae? I'll take it.
My well water is the same. Full of magnesium carbonate. At least the pH is right and it's a pH buffer too.. But I use either water from the dehumidifier or rainwater for use in the coolant system.
 
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