Coolant flush vs drain and fill

[1000MPH]

The Toyota maintenance schedule for my 4Runner says to replace initially at 100k/120mos then subsequently at 50k/60mos.
I changed the coolant in my 2010 at 9 years, 104k miles. I was planning on draining the block but the old coolant was so clean, and the block drains were so hard to get to, I opted for just the radiator drain and fill along with cleaning the res. I got about 4 qts out of my 11qt system. Other 4Runner owners were reporting they got as little as 1 additional qt from the block drain, but one person said they got 9qts out all together.
2 years later, 15,000 pandemic miles, I did another drain n fill. Just judging from the looks of the fluid, it was not necessary. Looking forward, I’m planning on a 3-4 year interval.
Edit: I forgot to mention, a Toyota recommended flush, if needed, is simply to drain and fill a second time with the premixed SLL coolant.

I might make a different plan if I owned a Jeep.

 

[doitmyself]

These and other threads about maintenance practices certainly bring out the biases that people develop based on personal experience, literature studied, internet drivel, etc.. What I find interesting (scary) is that some cannot accept other people's choices or that other choices are o.k. and work (or don't work). People state "to each their own", but inside they don't really believe that.

 

[supton]

I might make a different plan if I owned a Jeep

That is a good point, chemistry and model do have an impact. Also what was true in the past may not apply in the future.

 

[Snagglefoot]

A simple compromise might be to drain your rad and fill it with distilled water, run it for a while, than drain the rad again and fill it with 100% antifreeze. It’s better than just replacing the coolant in the rad, but not as comprehensive ( anal ) as flushing the rad. New coolants such as Prestone All Makes and Prestone North American Orange are 10 year coolants. Most folks won’t have to do this again unless they have specific rad or water pump issues. I suspect Dexcool will become a 10 year coolant as well but isn’t yet. Be cool.

My 2008 Burb has the original rad and water pump, changing once every 5 years with AC Delco or Prestone Dexcool, draining the rad three times and filling twice with distilled water and final fill with 100% Dexcool. I’m not going to bother with a second distilled water fill any more.

 

[350Rocket]

Not only the price of the part, but labour will cost more than the part itself.

Yeah it's a full days labor on most modern vehicles. Half a day on my truck. An hour on my cutlass.

 

[350Rocket]

A simple compromise might be to drain your rad and fill it with distilled water, run it for a while, than drain the rad again and fill it with 100% antifreeze. It’s better than just replacing the coolant in the rad, but not as comprehensive ( anal ) as flushing the rad. New coolants such as Prestone All Makes and Prestone North American Orange are 10 year coolants. Most folks won’t have to do this again unless they have specific rad or water pump issues. I suspect Dexcool will become a 10 year coolant as well but isn’t yet. Be cool.

My 2008 Burb has the original rad and water pump, changing once every 5 years with AC Delco or Prestone Dexcool, draining the rad three times and filling twice with distilled water and final fill with 100% Dexcool. I’m not going to bother with a second distilled water fill any more.

That's probably what I'll be doing in the summer when it's warm enough for no antifreeze.

 

[Donald]

Why ?

++1 - why?

 

[ollie]

Why ?

++1 - why?

Short answer is it's my personal preference. Long answer is all the busted knuckles and labor involved to change components over the years by following manufacturers flawed recommendations. This has put me off on extending simple maintenance. Case in point 2005 GMC Sierra my parents purchased used in 2009 with under 50,000 miles. Heater core was already leaking and the coolant not only tested bad but was filthy. I now own it and change it every 2 years like clockwork.


To be fair, I take pride in ownership and enjoy vehicles that are maintained meticulously. It is so easy and cheap to do simple coolant, diff, brake, power steering, engine, and transmission fluid services.

I do have to backpedal a bit though. I run Evens waterless in both my Beta and previously my KTM300. That pretty much gets left alone as there is no moisture to corrode. I do add or replace Evans when I wad up a radiator though. I would love to use it in my street vehicles but it's cost prohibitive to my budget.

These and other threads about maintenance practices certainly bring out the biases that people develop based on personal experience, literature studied, internet drivel, etc.. What I find interesting (scary) is that some cannot accept other people's choices or that other choices are o.k. and work (or don't work). People state "to each their own", but inside they don't really believe that.

Well stated. Heck, I don't care if someone else wants to beat up their rig or perform subpar and have low maintenance standards. It's my vehicle that counts because I'm the one driving it.

 

[Donald]

That's probably what I'll be doing in the summer when it's warm enough for no antifreeze.

There are anti corrosion and anti rust additives. I would never run straight water. I also believe that a proper coolant mixture transfers heat better than straight water or straight coolant.

 

[350Rocket]

There are anti corrosion and anti rust additives. I would never run straight water. I also believe that a proper coolant mixture transfers heat better than straight water or straight coolant.

I'm just talking like a couple hours or a day with water to help flush it out before adding in the proper coolant.

 

[walterjay]

I use test strips to determine when to do a coolant service. I just drain the radiator and refill. The new test comes out great.

 

[macarose]

It depends heavily on the type of vehicle you own.

Coolant tends to be one of those items that gets a good deal every now and then at the Products, Rebates, and Promotions section here. Plus, I sometimes get card rebates from the discount auto parts stores. Buying coolant along with a clearance item (wheel covers for older vehicles) tends to be one of my easiest casual buys. I own a dealership though so everything gets put to good use.

I would buy test strips first.

Second, the method you choose depends on how easy it is for you to do it. Some drain and fills are hellish. A full flush is usually far more expensive but if the drain and fill is a big hassle you may want to pay the extra money.

I owned a 1994 Toyota Camry that is still on the road with over 400,000 miles. At a time when coolant was $5, oil filters were less than $3 and Supertech was under $1 a quart I could over-maintain and not think twice.

Today powertrains are far more sensitive. Truth be told I would probably do the first one at 70k along with all the other fluids, and then all the fluids drain or in the case of power steering / brake fluid baste them out, and do it every 30k. I have a big bent on keeping what works forever and letting that be it.

 

[zzyzzx]

I've done work on 20 year old vehicles with the original coolant and everything looked nice and fluid looked good too.

 

[X15]

What's the point? Coolant is good for 100,000 or 150,000 miles. Why not just do a complete flush and change once and start fresh instead of adding new coolant to old, 4 or 5 times? That's like draining a quart of oil from your car every 1,000 miles and adding a new quart instead of just changing it all every 5,000 miles.

You're not changing it all though, there's still a not insignificant amount of old oil in the system, I don't really see it as being any different than doing a coolant drain and fill.

 

[X15]

Don’t some large engines do just that? Constant loss systems, something like that. Big engines, like ocean going.

Spill and fill is easier, done once or twice over the life of the car, goes the distance and off to the next owner.

Yes, there's engines like that.

More relevantly, the locomotive diesel engines that I can speak directly about have their oil sampled and sent off for testing every 15 days. When the lab says it's necessary the oil is "sweetened" by draining a quarter to half of the ~200 gallons, and adding the same amount of new oil. The oil is only ever completely drained and filled if it's found to be irreparably contaminated.

 

[Hillbilly Deluxe]

Most importantly After 100,000 miles you are at the point of coolant system repair/maintenance anyway. This is when your water pumps, radiators, houses and thermostats are starting to fail/need replacement. When you replace these parts you will be replacing more coolant anyway. Seems a waste to do a full flush/replacement...and go through that effort, only to have your water pump fail 10,000 miles later. IMO.

Maybe with Big 3 and some others. Toyota hoses are good for 15-20 years. Water pumps can go 200-300k miles. Radiators seem to be the weak point at 10-12 years for many.

 

[doublebase]

Maybe with Big 3 and some others. Toyota hoses are good for 15-20 years. Water pumps can go 200-300k miles. Radiators seem to be the weak point at 10-12 years for many.

Hoses I agree, they can last a long time, but water pumps? I’ve seen some fail as early as 50,000 miles, and yet others last 200,000. After 100,000 miles all bets are off for me.

 

[350Rocket]

Hoses I agree, they can last a long time, but water pumps? I’ve seen some fail as early as 50,000 miles, and yet others last 200,000. After 100,000 miles all bets are off for me.

Water pump is the most common failure on my Silverado and the original lasted 160k miles. Serpentine belt and AC belt were cracked and I replaced them but the hoses and rad are original and look in good shape (knock on wood). 17 years old.

 

[Gebo]

Drain the radiator, and then refill with the Lisle coolant funnel

The Lisle coolant funnel works like a charm. I can't imagine life without one.
You will thank slacktide if you get one...

 

[MichaelRS]

To each his own, but it seems just as much a waste to drain and refill the system every 20,000 miles when coolant is perfectly fine to over 100,000 miles.

- - Coolant analysis needed? - -

You really cannot count on that coolant being fine up to 100,000 miles in the real world. You don't know what stuff and junk, like heavy metals, is accumulating in your coolant from it running through your engine by that time slowly, or more quickly, degrading at the effectiveness and harming your engine and other components of your cooling system. Coolant can LOOK fine,but that means nothing.

They think about the oil and MAYBE the transmission, but I bet nobody ever thought to send their coolant out for analysis to someplace like Blackstone Laboratories after, say, 30-40k miles or more.

Doing said drain and refill is VERY cheap insurance tobnot only extending the life of a coolant but also the component parts of the cooling system and the engine itself.

Of course there's a point where the law of diminishing returns applies, like you wouldn't do it at every 5k oil change, but I don't see once a year or ~20K miles as being unreasonable if it makes one happy.