cooling system flush inquiry

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Old 10-21-14, 03:24 PM
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cooling system flush inquiry

I'm planning on flushing the cooling system on my '92 Accord. I have a can of radiator flush. Questions:
1. In addition to initially opening the radiator drain and allowing the coolant to flow out, Instructions say if the vehicle is equipped with an engine block drain, to open that drain and allow the engine block to completely drain as well. I definitely want to completely drain all the old coolant from the system including the engine block. The few times in the past I've ever attempted to remove the engine block coolant drain plug on other vehicles it's been other stuck/rusted in so tight it was nearly impossible to loosen, or located somewhere tucked behind something like part of the vehicle frame or whatever under there making it “inaccessible” without having to undertake some kind of extreme measure just to be able to get a wrench on it. If I encounter either of the above complications, is there a practical alternate method of thoroughly draining the engine block of all the old coolant, or is removing the block coolant plug the most reliable or best way to go if I can?

2. Instructions also say to let the engine idle with the radiator flush inside for at least 10 minutes, but “time and weather permitting” to “run the vehicle” for 3-6 hours with the radiator flush and water solution in the cooling system, which, it says, will provide a deeper clean and help to restore the cooling system to top efficiency. Should it typically be necessary to have to run the vehicle for 3-6 hours as suggested with the flush chemical stuff? And if so, would just idling in the driveway be okay, or should the 3-6 hours of “running” the vehicle be like on the road at driving speeds?

Any comments appreciated!
 
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Old 10-22-14, 03:21 AM
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IMO using the radiator petcock or if it doesn't have one, removing the bottom hose is sufficient. I like to run the cleaner for a day and then rinse the system although a lot depends on how dirty/clean the cooling system is.
 
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Old 10-22-14, 09:43 AM
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IMO using the radiator petcock or if it doesn't have one, removing the bottom hose is sufficient
Well I do have radiator petcock which of course I plan on opening, but if I additionally disconnect the bottom hose does that ensure complete coolant drainage from the engine block, just as removing the coolant engine block drain plug would?
 
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Old 10-22-14, 10:48 AM
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As long as you can open the petcock I wouldn't take off the bottom hose, I don't think it would drain any better - just faster. As the last step in flushing the system I like to run the engine with the petcock open along with a water hose replacing the lost water.
 
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Old 10-22-14, 11:20 AM
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As long as you can open the petcock I wouldn't take off the bottom hose, I don't think it would drain any better - just faster. As the last step in flushing the system I like to run the engine with the petcock open along with a water hose replacing the lost water.
But just opening the radiator petcock doesn't drain the block too, which is what I'm wanting to accomplish. If I am understanding correctly though, you're saying that to make sure I am flushing the block in its entirety also, I just need to run the engine with the petcock open while running a water hose into the radiator. Is that correct? If so, for how long probably.
 
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Old 10-22-14, 12:18 PM
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I always cut a flush tee in the heater core inlet on my cars and trucks.

This back flushes it to the rad.

I ride around with the flush in the car for a day or two before I flush..

Been using this product 30 years or so..

 
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Old 10-22-14, 12:20 PM
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Old 10-22-14, 12:25 PM
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Old 10-22-14, 12:39 PM
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opening the radiator petcock doesn't drain the block too, which is what I'm wanting to accomplish
I believe you are over thinking it. Whatever coolant is in the block doesn't stay there as it all gets circulated throughout the system. Running the engine up to operating temps with the cleaner will make sure it goes thru the entire system, rinsing the same way removes the cleaner from the whole system. I used to use a back flush kit similar to the one Mike does but it broke or got lost long ago and I've never bothered to replace it
 
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Old 10-22-14, 01:30 PM
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I believe you are over thinking it. Whatever coolant is in the block doesn't stay there as it all gets circulated throughout the system. Running the engine up to operating temps with the cleaner will make sure it goes thru the entire system, rinsing the same way removes the cleaner from the whole system.
I see. Thanks marksr. Yeah like you said it'll probably be just fine to do just as you suggest. But it's just that on this vehicle, as is probably the case with most these days, the radiator petcock is not the lowest point in the cooling system, and also, as I've been informed, even the actual engine block coolant drain plug isn't either, although I do think it is somewhat lower. Regardless, even if I do open the block plug in addition to the petcock, if I wanna make sure every bit of the old coolant and/or flush chemical is rinsed out, I guess I should fill/drain several times, while the engine is up to operating temps, or maybe better yet (because faster not having to wait for it to open) with the thermostat removed temporarily?
 
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Old 10-22-14, 01:32 PM
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If you go thru the trouble of removing the thermostat I'd go ahead and replace it and the gasket. While we always strive to remove all the old anti-freeze and whatever cleaner is used - it won't hurt anything if minute amounts of the old get left in the system.
 
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Old 10-22-14, 01:36 PM
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Yeah and thanks Mike for reminding me about the Prestone flush n fill kit for backflushing, and the video instruction links because I kind of forgot for sure how to use that business properly. I have used those before, and in fact have the tee installed on my Ranger and have used it, but not in my car for some reason. I probably still have the rest of the kit lying around and should probably go that route with my car too I suppose, for this flushing business.
 
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Old 10-22-14, 01:45 PM
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If you go thru the trouble of removing the thermostat I'd go ahead and replace it and the gasket. While we always strive to remove all the old anti-freeze and whatever cleaner is used - it won't hurt anything if minute amounts of the old get left in the system.
Okay, thanks again marksr. Good point about the thermostat and gasket. And I do think I realize minute amounts of the old coolant or cleaner might be okay, but just would like to be particularly sure this next time I've drained/flushed as much as possible and am going about it properly, not leaving much more than the "minute" amount.
 
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