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#892460 - 05/03/07 04:56 AM How to adjust antifreeze pH?
jzmtl Offline

Registered: 03/24/07
Posts: 9
Loc: Montreal
What chemical do I use to increase pH of antifreeze? Is sodium hydroxide okay? I tried google but no one is saying what to do besides get a cooling system flush.

#892461 - 05/03/07 06:35 AM Re: How to adjust antifreeze pH? [Re: jzmtl]
George7941 Online   content

Registered: 05/10/05
Posts: 1941
Loc: Toronto, Canada
I don't think anybody uses a chemical to increase the pH of coolant. If your coolant is that acidic it is time to replace it anyway. There are other additives in coolant that will be depleted by the time coolant becomes acidic.
2006 GMC Sierra 4.3l, NV3500,G80 , Formula Shell Synthetic 5W30,Dexcool.
1987 BMW R80 - sold
2015 Honda CBR300R

Staying out of the right lane a lot.

#892462 - 05/03/07 06:50 AM Re: How to adjust antifreeze pH? [Re: George7941]
jzmtl Offline

Registered: 03/24/07
Posts: 9
Loc: Montreal
That's the thing, the coolant is new. From what I read pure prestone is 10.5, but afte mixing with water it's down to 9.

From description of coolant flush, they say after adjust coolant/water ratio, they use a pH concentrated coolant to adjust pH. So they must use some sort of base to get it right, but no one is saying what.

#892463 - 05/03/07 07:48 AM Re: How to adjust antifreeze pH? [Re: jzmtl]
onion Offline

Registered: 02/04/07
Posts: 2097
Loc: kansastan
Sodium hydroxide is some pretty strong stuff... I'd be cautious about it. Sodium bicarbonate works fine for aquariums...

What PH are you looking for? Why?
The invisible and the imaginary look exactly the same.

#892464 - 05/03/07 07:08 PM Re: How to adjust antifreeze pH? [Re: onion]
jzmtl Offline

Registered: 03/24/07
Posts: 9
Loc: Montreal
from around 9 to 10.5, because that seems to be the optimal pH for antifreeze.

#892465 - 05/03/07 07:13 PM Re: How to adjust antifreeze pH? [Re: jzmtl]
benjamming Offline

Registered: 01/03/04
Posts: 5861
Loc: northern Alabama
But you say that you have a pH of 9 right now & are targeting 9-10.5. Tell us again why you are wanting to adjust the pH.

#892466 - 05/03/07 09:20 PM Re: How to adjust antifreeze pH? [Re: benjamming]
John K Offline

Registered: 09/06/03
Posts: 950
Loc: Loveland, Ohio
Sodium bicarbonate will typically raise the pH to less than 8.5. It 'sounds'(?) like you are assuming that 10.5 is the ideal pH because that is the pH of concentrated antifreeze. I think that a pH of 9 should be fine. Depending on what type of water you mixed with the antifreeze you run the risk of elevating the pH too high using sodium hydroxide. Higher pH is good for iron/steel, not sure of optimum for aluminum, but if you have any copper in the system raising the pH would not be a good idea.

#892467 - 05/03/07 09:28 PM Re: How to adjust antifreeze pH? [Re: John K]
John K Offline

Registered: 09/06/03
Posts: 950
Loc: Loveland, Ohio
Well, I did a search and found an MSDS for Castrol antifreeze that listed the pH as 10.5-11.0 for 50% antifreeze. If that is what your pH should be and it is at 9.0, it probably means inadequate rinsing of an acid cleaner or dilution with some hard water??? If there are contaminants in the coolant then I think you'd be better off replacing the antifreeze, rinsing, and using distilled water to dilute the new stuff with.

#892468 - 05/03/07 11:59 PM Re: How to adjust antifreeze pH? [Re: John K]
1sttruck Offline

Registered: 03/20/04
Posts: 4378
Loc: Camas, WA
I like using 50% coolant as a flush, and just buy twice as much when changing it. One of the reasons is to let the flush have first crack at dealing with remaining chemical issues in the system, so that the coolant intended to remain in the system starts off as designed, with the best shot at coolant life. Coolant isn't that expensive considering how long it remains in service, compared to engines with corroded, leaky freeze plugs and other such things from poorly maintained cooling systems (two friends have had this problem).