Another successful Citric Acid flush

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Aug 15, 2006
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Central Washington
Decided to give the citric acid flush a shot in my recently acquired 2003. My usual method is to drain and fill 3 or 4 times with not very good results usually.
What I started with.


After draining the coolant, I installed a dummy thermostat I cut the center out of, and a 3/8 NPT ball valve on the block drain to make it easier for me to open and close it all the time. I can only access the left side block drain unfortunately which leaves some of the capacity in it. Book capacity is 4.8Gal and after draining both taps I can get about 2.5 gallons back into it, the rest being in the heater core and right side of the block.
Then I flushed it for about 10 minutes with both drains open at 2500rpm. I didnt have a flushing Tee, I just stuck the hose into the coolant tank which seemed to work fine.
Closed the drains, dumped about 2 lbs of citric acid powder into in and filled it up. Closed the cap. I ran it for a bit more than 5 minutes, again at 2500rpm, at which point it was up to 190F and starting to spit out the coolant cap.
I ended up letting it sit for about 20 minutes while I ate dinner before I drained it.
Stuck the hose back in and filled it, ran it about 10 minutes at 2500 with the taps open again.
Then I let it idle while I dumped 10 gallons of distilled through it. I wanted the remaining water in the system to be distilled or close to it.
Removed the ball valve, reinstalling the plug and took out my dummy thermostat for a new one. I also popped a core plug and installed a block heater.


What was most impressive to me was it actually managed to clean the coolant tank. I thought I was going to have to replace it to be able to see through it again. But its fine. There isnt I huge amount of flow in there so I thought it wouldn't do a very good job.
To fill I added 2 gallons of straight G05 and then topped up with 50/50. I also added RMI while I was at it. Ill test the concentration later this week, but it should be in the ballpark.

Bonus shot of the inside of the block after I popped the core plug out. This was post flushing.
 
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I would revoke your "man card" IMMEDIATELY for draining coolant into your used oil pan.

It actually [censored] to see that. You couldn't get another container?
 
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Originally Posted By: Linctex
I would revoke your "man card" IMMEDIATELY for draining coolant into your used oil pan.

It actually [censored] to see that. You couldn't get another container?


lol.
Thats my dedicated coolant container. Hence the green color. My oil one is black.
 
Originally Posted By: Linctex
I would revoke your "man card" IMMEDIATELY for draining coolant into your used oil pan.

It actually [censored] to see that. You couldn't get another container?


How dare you, Colt45ws. You know this kind of thing pisckses BITOGers off after they've had a few!
crackmeup2.gif
 
Originally Posted By: Linctex
I would revoke your "man card" IMMEDIATELY for draining coolant into your used oil pan.

It actually [censored] to see that. You couldn't get another container?

Maybe I am thinking you were trying to be funny but failed?

I have a similar container that oil and fluid goes in and I clean it out in between. I recall dad using it in the early '70s on the Chevys then, still the same container doing duty now. Did I fail to follow some unknown (to me) pattern and recycle it a decade ago to buy a Chinese one now? (Goak!)
 
I have never had to use 2 pounds of an acidic cleaning product in my cooling system so I am not familiar with acceptable or recommended practices.

Plus I always use a T.

You mention, "Book capacity is 4.8Gal and after draining both taps you can get about 2.5 gallons back into it, the rest being in the heater core and right side of the block." So your vehicle leaves 2.3 gallons in the system? Almost half capacity? Are you sure a 10-gallon flush removes all that acidic solution?

Was the cooling system not working efficiently before.

BTW, I do like the color coded drain pans and green for coolant even more.
 
Originally Posted By: ArcticDriver
I have never had to use 2 pounds of an acidic cleaning product in my cooling system so I am not familiar with acceptable or recommended practices.

Plus I always use a T.

You mention, "Book capacity is 4.8Gal and after draining both taps you can get about 2.5 gallons back into it, the rest being in the heater core and right side of the block." So your vehicle leaves 2.3 gallons in the system? Almost half capacity? Are you sure a 10-gallon flush removes all that acidic solution?

Was the cooling system not working efficiently before.

BTW, I do like the color coded drain pans and green for coolant even more.


Before I flushed with the 10 gallons of distilled I first flushed with hose water. However many gallons went through it in the 5-10 minutes it was running with the hose stuck into the coolant tank. It was working fine, a little cool due to a lazy thermo. I just wanted to remove as much of that old rusty coolant I could and any deposits it left behind.
 
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Nice job. FTR my coolant container is green too. But it has seen an occasional oil change, only if two vehicles need an oil change the same day.
 
Heck, I have a green one of those for green antifreeze, and a yellow one for G-05/Premium Gold! And several of the covered black ones with the drain hole in the middle for oil.
 
Originally Posted By: Colt45ws
Originally Posted By: Linctex
I would revoke your "man card" IMMEDIATELY for draining coolant into your used oil pan.

It actually [censored] to see that. You couldn't get another container?


lol.
Thats my dedicated coolant container. Hence the green color. My oil one is black.


Owned!
 
Looks great but for future reference try using baking soda in the rinse water to neutralize any remaining acid, 8 tablespoons per gallon system capacity should do it, do it twice then a clean water rinse without.
You got the amount close enough for your system 1.1lb for a 2.3 gallon cooling system is recommended by MB but on an older system with aluminum radiator and heater core I would probably use 1lb and do it twice if necessary after flushing it again with clear water just to keep the percent of acid lower. If the sytem has ever used a sealer like GM tabs, bars, etc do no flush it with acid, every leak will return possibly worse than it was originally.
 
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What's the issue with using an oil drain pan for coolant? Just asking as I only have one pan and never gave it a thought.
 
Originally Posted By: Trav
Looks great but for future reference try using baking soda in the rinse water to neutralize any remaining acid, 8 tablespoons per gallon system capacity should do it, do it twice then a clean water rinse without.
You got the amount close enough for your system 1.1lb for a 2.3 gallon cooling system is recommended by MB but on an older system with aluminum radiator and heater core I would probably use 1lb and do it twice if necessary after flushing it again with clear water just to keep the percent of acid lower. If the sytem has ever used a sealer like GM tabs, bars, etc do no flush it with acid, every leak will return possibly worse than it was originally.



Ill note that for in the future. You dont think I really had any left? After flushing it out for so long?
And that was the recipe I was trying to use. I don't think its used any sealant. Im already keeping an eye out for leaks. Ive got to do the final topup and then I should be able to see where it goes.
 
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I doubt you have any left and I wouldn't do anything at this point but next time its worth keeping in mind, citric acid and thin aluminum tubes don't play well together.
 
My understanding was that citric acid is safe to use with aluminum components.

I've been doing citric acid flushes on my Barracuda and my engine's internals look freshly cast. See Cooling System.
 
I would say safer or safest acid is more like it. I have read all kids of theories about it, that it strips off the naturally formed protective layer allowing the aluminum to corrode quickly after cleaning and things like this. I'm no chemist but there are reports of issues that I think its safer to neutralize acid than be sorry later.
 
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