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Old 05-04-2013, 06:58 AM
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Default Oxalic acid to flush cooling system?

Anyone use oxalic acid to flush their cooling system?

GM had a TSB (99-06-02-012D) on flushing a dexcool system (with sludge) using Prestone Heavy Duty Cooling System Cleaner, GM P/N 12346500. However it is not avail anymore. The main ingredient in the cleaner is Oxalic acid (wood bleach) and the neutralizer is Sodium Carbonate (Arm & Hammer Super Washing Soda).

I found these instructions:

To use:
- Drain and flush the cooling system.
- Fill it back with clean water and add the Wood Bleach.
-Run it for an hour, or longer, and make sure the engine is up to operating temperature.
-Drain the Wood Bleach solution and see what the cooling system now looks like.
-If not yet clean, flush the system and then repeat the treatment.
- When clean, flush the system, replace with clean water and the two ounces of the Washing Soda.
-Run for another hour, drain and flush well. (This neutralizes the oxalic acid in the Wood Bleach)
- Replace with your new anitfreeze solution.

Thinking of trying it when I replace my thermostat & switching to Peak Global lifetime antifreeze.
2000 DII 7 pass w/ SLS, ACE, Sunroofs, Rear A/C, Cold Weather Pkg.
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Old 05-04-2013, 07:06 AM
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The problem is that if you have sludge and scale, like in a 120,000 mile truck, which has been cooked in there for thousands of hours, the chemical flush for a few minutes may not get it all. Doing the flush every three years would produce better results.

Citric acid packets are also used (Mercedes) in aluminum radiators and aluminum heads. Some people have also used 20 Mule Team Laundry Booster, and driven a week.

Old style radiators with metal side tanks (D1) can be rodded out by a shop. Plastic tank rads like the D2 usually can't do this because tanks are so brittle.

But all this assumes you have sludge, which can be detected by testing temperature on the fins, top to bottom, vertical line, warmed up, engine off. 10F or more cooler on bottom rows shows low flow. My D1 rad, rodded out, shows within 5 degrees top to bottom.
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Old 05-04-2013, 07:39 AM
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Sure you can try it. it might work. I would make sure to use Distilled water. as regular tap has minerals impurities etc... Also I would say if you are questioning the capacity of your radiators efficiency instead of taking the hours to flush which is suspect at best. to just replace you radiator. if you have over 100K you radiator is not working at full spec anyway. This way you know that your system is now at peak capacity with the new thermostat and the better coolant. TO me the flush stuff is along the lines of snake oil. The other concern is the water passages are small. lets say you do the flush are you certain that you have flushed out ALL the loose particulate from the scale build up. Has some of it lodged itself int he passage ways. You do not know. just my 2 cents.
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Old 05-04-2013, 08:28 AM
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Once factories went to plastic tank radiators they are considered wear out parts just like hoses. D2 rads are pretty slim inside, and those white chunks are calcium that has cooked out of the non-distilled water. Well water is the worst, plenty of minerals which make it good for Tennessee whiskey. In my town, the industrial district water comes from the river. But the rest of town gets theirs from deep wells. So always try to use distilled or premix 50/50.

The calcium and scale may reduce in size from various chemical treatments, but you are not dealing with a thin "surface frosting" like the inside of a light bulb.
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Last edited by Savannah Buzz; 05-04-2013 at 08:39 AM.
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Old 05-04-2013, 01:41 PM
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I've done some math before on another thread about money wasted trying to flush one of these radiators.When you figure in cost of fluids and your time, it is just as cheap and easy to go on and replace with a $130 radiator from genesis.

I'm not doubting your ability to flush the radiator, but if you're already replacing the thermostat why not start with a new radiator too.

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Old 05-04-2013, 01:41 PM

990602012d, acid, aluminum, bleach, boil, clean, cleaner, cooling, forum, gm, instructions, oxalic, radiator, system, tsb, wood

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