When changing coolant should you flush....

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gregk24

gregk24

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I am planning on doing a coolant drain and refill on my Accord this Thursday. I already have two gallons of Honda Type 2, a funnel, and a clean drain pan. The process seems easy enough, but I have two questions...
1. I have never done this before, do I need to heat up the car fist before draining? If so, how long do I wait before opening the rad cap so I dont burn myself...part 2...if I dont drive it around first and just drain it cold, Ill have to start it up to get the bubbles out but it would take probably 20 minutes or so of idling to heat it up (not good).
2. After draining the coolant, should I "flush" with distilled water or is this not necessary.
Any other tips or advice are totally welcome! Its the Accord in my sig.
 
I wouldn't drain it hot, you can burn yourself. I'd do this:

-on a cold engine, open the petcock of the radiator and let it drain
-tighten the petcock back up and refill the radiator
-using a spill free funnel with the correct rad. cap adapter, fill the funnel half full
-start the car and let it get warm until the cooling fans come on, burp all air out of the system (until you see no bubbles in the funnel)

IMO, you don't need to get all coolant out and do a complete evac. and replace. I'd do two of these drain and refill procedures, the revisit the topic in two years.
 
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I'd do it first thing in the morning when the car's cool. All Honda's need are periodic radiator drain & fills. No flushing with distilled water is really required. The only time a flush is warranted is when you have non-Honda coolant in the system. Blue Honda Type 2 isn't compatible with the green all makes/models generic coolant, so the system would require flushing to remove the old stuff first. Also remove the old fluid from the overflow tank and refill.

The coolant in my sig. Accord is also due. I'm just going to wait til the summer when I do the timing belt & water pump.
 
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Do not flush. There's rarely a reason to unless the manufacturer requires it (which Honda does not) or if it was contaminated with oil.

Do the drain/refill when it is cool. Remove the peacock valve, then open the radiator cap. Allow it to fully drain - this can take up to 1hr.

Close the drain valve and refill slowly. Use a lisle coolant funnel with the right adapters.

Fill the coolant until you have a small amount inside of the coolant funnel. Start the car and allow it to run until the thermostat opens, which is when the fan comes on. Allow this to occur at least twice. It can take 30-45 minutes.

Once that is all done, close the cap and top off the reserve bottle.
 
As a matter of personal preference I drain/fill my rad yearly. Probably more often than needed but coolant is dirt cheap. Always fresh coolant, no worries.


Most radiators have a drain valve on the bottom that will allow you to drain at least a couple quarts out. FWIW I've found that using a thermostat with a jiggle pin, or taking your current thermostat and drilling a very small hole near the perimeter helps with draining on some vehicles. Crack loose the radiator cap and loosen the drain valve

Doesn't really make a difference whether the car is hot or cold when doing it. Just grab a spill free funnel kit and use that to burp all the air our and you'll be good to go!
 
I'd decide any intermediate steps based upon what comes out first. If you see any grit or dirt you might want to fill once with distilled or even hose water first before you refill.

Personally, since hose water is free, and distilled is cheap, I usually drain by the petcock, fill with hose water, drain, fill with distilled, drain, then fill with my 50/50 mix. If I'm lazy I'll just do one of the intermediate fill and drains.

Our water quality is good and even if not, the remnant tap would be minimal enough to not be an issue. But it's another chance to get any junk out, so I like to do it. Even with burping air, and using distilled, it's maybe 10 minutes and $1.
 
Do you not have drains on the block?

If I have not done a drain/fill in a while, I like to open the block drains to get as much old out as possible. I only do a simple radiator drain/fill if the coolant was done in the last 2 years or so.

If your '06 has NEVER been done, then I'd drain the block, radiator and refill with distilled water. Run it until the thermostat opens and run the heater. THen let it cool and drain the block and radiator again. Then I'd fill with 60/40 so as to get a 50/50 final approx. mix considering the undrained portion in the heater core.

If it has had a drain/fill a few times, and has the correct coolant in it now, then that is not necessary.
 
When I change the coolant on our 05 2.4 accord, I drive it around for 5-10 min with the heat temp on hi for the last minute, shut down, then open the radiator drain (it's hot) and let it drain until no more comes out. Only opening the radiator drain will usually drain the little reservoir too. Then I open the rad cap, and it drains some more. Then refill the radiator to the top and let it sit for a while and it will settle a bit, then fill it up again, and the reservoir. Put the cap on, hose off the coolant that spilled in the under tray, then drive around the neighborhood with the heat on until it warms up. After it cools check the levels and top off as needed.

I've never flushed, there's never any crud in it, the old type 2 coolant looks as good as the new stuff that goes in.
 
Yeah the long life and low/no silicate coolants have really changed the game. Even in old,,old cast iron engines like my MB diesels. Clean as can be.

Which is why removing hoses, block drains, thermostats,,etc., no thanks for routine upkeep. If/when I do something like a thermostat change, then I can completely wash out the whole block. Or IF I have an issue that needs to be solved.

Modern chemistries just do a good job, which means that a drain and refill of the radiator is really the only step for success it seems. Others can keep,and use the old green stuff. For me? No thanks.
 
So guys, a few of you are recommending a coolant funnel. Is this really necessary? Is using a regular funnel really that hard?
 
Originally Posted By: gregk24
So guys, a few of you are recommending a coolant funnel. Is this really necessary? Is using a regular funnel really that hard?


It's nicer than dribbling coolant on the rad neck which will then smell when it bakes off. Depends on your level of OCD.
 
It's a lot easier to burp the system with. Plus any coolant left in the funnel after you plug it off, can be put back into the jug.
 
Do it cold. No need to flush except if the coolant is very dirty. Fill with 50/50 approved coolant and DISTILLED water. Some vehicles need to be purged of air when you are done, check your manual.
 
Originally Posted By: eljefino
Originally Posted By: gregk24
So guys, a few of you are recommending a coolant funnel. Is this really necessary? Is using a regular funnel really that hard?


It's nicer than dribbling coolant on the rad neck which will then smell when it bakes off. Depends on your level of OCD.


I skipped the funnel, and used premixed coolant, and look forward to using a funnel next time. Just less mess. Not sure what I did, but the first two gallons came out fine, but the third gallon wanted to dribble every which way when I was pouring.
 
Originally Posted By: gregk24
So guys, a few of you are recommending a coolant funnel. Is this really necessary? Is using a regular funnel really that hard?


Nah, just use a normal funnel with a long neck. Stick it down in the radiator hole and fill up. Keep an eye on the fluid level so you don't fill too fast and spill.

You can usually tell the approximate level by the noise the fluid makes - as the level goes up, so does the pitch of the gurgly/swirly noise.

Those funnels are a nice-to-have, not a need-to-have
 
I always do a drain and flush on my older cars. They have block-drain petcocks, so its very easy to flush them with the garden hose, drain, flush with a gallon of distilled water, let that drain, and then refill with an exact 50/50 mix.

On the newer cars (Challenger, JGC) I'll just do a drain and refill with 50/50 mix. When you can't drain ALL the water out, you'd be left with an uncertain coolant/water ratio if you flush. You can tweak it back to the right ratio with a specific gravity tester, but with modern coolants there's jst no reason. Infusing a shot of fresh coolant/additive is all that's really necessary.
 
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