simple siphon coolant drain and fill

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Honda CR-V 2014 40,000 miles. I had an idea for a simple coolant exchange. I'm not interested in a full on flushing of the radiator, but just looking for a simple way to keep the coolant fresh annually or biennially; hopefully to avoid the need for a full flush later.

The coolant reservoir is tee'd into the radiator cap. I opened the cover of the coolant reservoir, but kept the fill hose submerged in coolant. I opened the petcock which started to siphon fluid up from the reservoir as coolant drained out from the base of the radiator slowly. I kept the reservoir topped up to keep the siphon primed. I did this until I had added 1 gal of total coolant to the reservoir. Then I shut off the petcock when the reservoir was at the "max" line.

Seems like I exchanged about 1 gal of old coolant for 1 gal of new, minus some mixing losses. Shouldn't be at risk for air bubbles since I never broke a line. Is this already a thing? Does anyone else do this? Did this accomplish what I had hoped? Is there any merit to the approach of doing this every 1 or 2 years?
 
That's how I've always done mine. Sort've a larger scale "turkey baster" method
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Never tried your method but if it works that's great. I do mine every 2 years by pulling the bottom radiator hose. Then just refill. Just check levels after a hot cold cycle a few times. Only time I would back flush was if there was a problem like overheating or low heat from the heater.
 
Thanks for the comments. Maybe I'll try pulling the lower hose next go round just to see.
 
I opened up the petcock on my Liberty drained the radiator, pumped out the recovery tank, tightened up the petcock and refilled it with a 50/50 mix of G05 and distilled water. I burped it and called it a day. The coolant that came out was clean, the radiator was clean, and the coolant tested good. I have no intentions of flushing the cooling system if things continue to look clean, there are no problems, and the coolant stays good.This was the second time I did it that way.
 
I pull the bottom hose to get the "rush" of coolant that will take some from the block. Then I remove the drain plug(s) on the block, as its amazing how much remains in the block. Then remove a heater hose and blow compressed air in to clean it out
 
Your technique seems similar to a brake fluid flush.

Two comments on your technique.

1) If you can, I'd say suction out the overflow tank first and replace that with new fluid instead of having that stuff flow into your system. The worst dried gunk always seems to be on the sides of the overflow tank as it gets some interaction with fresh air. it may even be better to try to suck/fill the overflow tank a few times over a few days to get that "rinsed" before beginning your technique.


2) The coolant tank MAX level is often the HOT line. Since you're doing this cold, and focused on no air bubbles; you should try to target somewhere around middle or so and not at max. So I would've drained lower to the middle instead of stopping at max. If you are at max, when it heats up, some of your fluid may overflow and just drain out.
In a regular service, you often initially go to MAX, because of the inevitable bubbles in the cooling system end up bringing it down anyway .
 
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I've new er seen anyone do an exchange this way. So all you did was add coolant to the overflow tank as the old coolant flowed out the bottom of the radiator? And this worked? There was enough of a vacuum to siphon coolant through the overflow tube, into the radiator? I may give this a try if so. Sounds like an easier/less mess, less air bubbles to bleed procedure.
 
Originally Posted By: Eddie
I prefer pulling the bottom hose also. Ed


+1 It maybe old school but I always felt it was the easiest way to do a drain and fill. Just get ready for a tidal wave when you pull the hose.

A really cool idea though. Pretty smart!
 
Hi:

I think this is a clever idea but I would want to clean out the reservoir first before proceeding and fill with fresh coolant. So the way I understand this is that you open the petcock and just make sure you keep replenishing the reservoir tank as it is draining?

I always just do simple drain and refill, no removal of lower hose or block plugs, and then very slowly fill new coolant using funnel trying to be careful not to pour gulps in and trap air. Then, I let the engine run with the radiator cap off to try and burp and air and wait till the fans come on a few times. Is that generally sufficient to bleed air? I read some folks raise the front end to help bleed the air but I've never done this.
 
As long as the reservoir is above the outlet and the line stays immersed at the top end, the siphon will work - part of the convenience of a siphon. It's the home brewer in me that got the idea. From feedback, if I don't pull the hose next time, I agree that replacing reservoir fluid first makes sense, and that potentially MAX line may be too full for cold fill. Thanks guys.
 
What I like about your method is that presumably if done right you don't get air into the system so no worries about bleeding the system, right? But I guess you absolutely need to keep the radiator cap on to maintain the vacuum required for the siphon. I think I will try this for my next coolant change. Thanks for posting this.
 
In my experience owning many old used cars for the last 20 years, changing/flushing coolant in a 4 year old car with only 40,000 miles is a waste of time and money. The coolants and materials used in the cooling system are far better than they used to be. I would wait perhaps 8 years/100,000 miles before considering spending any money in this area. Just my opinion.
 
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