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Thread: Oxalic acid flush, created something when neutralized..

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    Default Oxalic acid flush, created something when neutralized..

    Gave oxalic acid a shot for flushing rust particles out of my cooling system.
    OK I used 3 TB spoons of oxalic acid mixed in with distilled water after flushing the coolant out of my cooling system. Things looked great until i flushed and added the soda ash. A green/blue "film" formed on the block drain plug and a spotted film of the same color is present when looking through the radiator cap. Haven't taken the hoses off yet. Looks like a very thin layer of paint . Not a sludge or "growth".

    I drained the base and right now theres fresh distilled water in the system. Any suggestions on how to proceed? I'm not a chemist and dont pretend to be. Will adding a small amount of acid back in remove the varnish created?

    Goggle has revoked my IP address from over use. (kidding) It appears i created a copper something... caused by the acid+base reaction.. Not a lot on removing it though.. or if its harmful to the cooling system.

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    Default Re: Oxalic acid flush, created something when neutralized..

    Couldn't tell you how to remove the film it but I would be careful of the ph value. I would check the ph of your coolant or whatever you have in your cooling system right now. I believe the ph has to be above 8.5 to prevent any corrosion.
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    Default Re: Oxalic acid flush, created something when neutralized..

    I don't know anything about the soda ash flush, I was taught that Arm & Hammer baking soda was the ticket for the best acid neutralizer when working with Oxalic Acid, its worked for me for over 30 years. I've never seen any type of residues left over.

    1 Wear Eye Protection and Gloves

    2 I always remove the thermostat, make sure the engine is totally cooled down.

    3 I use one of those Prestone flushing tees, and flush it out really good to remove all the anti-freeze while its running with no radiator cap on, (NEVER have anything below the radiator cap open or you risk the water level dropping, which will equal a BHG). until you're sure you have it all flushed out.

    4 Add about a half cup of Oxalic Acid into a white painters bucket, ADD WARM water and thoroughly mix it until you don't see any crystals.

    5 Making sure your engine is ice cold, remove enough water to make room for your Oxalic Acid Water Mix, pour it into the radiator, put a LEVER Type radiator cap back on, run it until it warms up maybe 15 mins., make sure your heater is turned on so the mix also passes through that part of your cooling system.

    6 Carefully lift the lever and remove the pressure through the cap, then remove it, flush it slowly until so you don’t pump ice cold water into a warm engine, do it slowly so the engine cools slowly.

    7 Once the engine is ice cold again, Mix a box of baking soda in a white painters bucket ensuring its mixed with the water well, drain the radiator enough to allow the baking soda water mix and pour it, put the cap back on run it until its warmed up again, and repeat the cool down flush process, flush it really well until your sure all the baking soda is removed.

    8 With the engine again ice cold. open all the drains and remove as much water as possible, reinstall your thermostat, close everything up, and fill with antifreeze.

    That’s pretty much the process I've always used, would love to hear others.

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    Default Re: Oxalic acid flush, created something when neutralized..

    ok had a chance to pull the thermo housing. Only the brass/copper sensors have the wierd green/blue coloring. Not the entire sensor tip though, just around the sensor base. Now there is a nice thin layer of rust on the walls of everything i can see. Not solid, it wipes off easily The stuff in the radiator is luiquified rust too. Soo looks like i need to do a better job with the flush.. May re do the acid step and flush it 2 -3 times before adding the base. Another option is to try a dishwasher detergent..

    I havent been able to locate ph test strips at auto parts stores here.. If pool test strips work I can get some of those instead..

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    Default Re: Oxalic acid flush, created something when neutralized..

    Quote Originally Posted by suprageezer View Post
    I don't know anything about the soda ash flush, I was taught that Arm & Hammer baking soda was the ticket for the best acid neutralizer when working with Oxalic Acid, its worked for me for over 30 years. I've never seen any type of residues left over.

    1 Wear Eye Protection and Gloves

    2 I always remove the thermostat, make sure the engine is totally cooled down.

    3 I use one of those Prestone flushing tees, and flush it out really good to remove all the anti-freeze while its running with no radiator cap on, (NEVER have anything below the radiator cap open or you risk the water level dropping, which will equal a BHG). until you're sure you have it all flushed out.

    4 Add about a half cup of Oxalic Acid into a white painters bucket, ADD WARM water and thoroughly mix it until you don't see any crystals.

    5 Making sure your engine is ice cold, remove enough water to make room for your Oxalic Acid Water Mix, pour it into the radiator, put a LEVER Type radiator cap back on, run it until it warms up maybe 15 mins., make sure your heater is turned on so the mix also passes through that part of your cooling system.

    6 Carefully lift the lever and remove the pressure through the cap, then remove it, flush it slowly until so you don’t pump ice cold water into a warm engine, do it slowly so the engine cools slowly.

    7 Once the engine is ice cold again, Mix a box of baking soda in a white painters bucket ensuring its mixed with the water well, drain the radiator enough to allow the baking soda water mix and pour it, put the cap back on run it until its warmed up again, and repeat the cool down flush process, flush it really well until your sure all the baking soda is removed.

    8 With the engine again ice cold. open all the drains and remove as much water as possible, reinstall your thermostat, close everything up, and fill with antifreeze.

    That’s pretty much the process I've always used, would love to hear others.
    I followed this:
    For a heavy clean three tablespoons. For a minor clean one. Drain coolant and remove T stat. Refill with water and add oxalic. Run for a total of about one hour. Drain, refill with water and neutralize with one tsp soda ash (bicarbonate) for 30 minutes. Drain, fill with water, drain (better is to remove lower hose and back flush), fill with coolant mix.-Jetjock
    I think I'll avoid soaps and do another acid fill with several drain & fills before going to the base. Just realized my error, i used a tb spoon of soda ash.. I wonder if jetjock tried his recipe out in his meth lab to get the dosage suggested.. Knowing him from the forum, probably so.

    Thermostats already out. Getting above 160* is damn near impossible. drove around for an hour today and temps stuck solid. Thats a good thing or so I've read.

    I've been doing all the flush/fill with distilled water, walking out of wally world with 15 gal.s of water I had a few "what does that guy know that i dont" looks. Somebody went home and googled 2012 I'm sure..

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    Default Re: Oxalic acid flush, created something when neutralized..

    While flushing I would just use tap water from the hose, then add the distilled when you put the coolant in.
    “Life is hard; it's harder if you're stupid.” - John Wayne

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    Default Re: Oxalic acid flush, created something when neutralized..

    Huh. Can't say I've ever seen that. Maybe you left the neutralizer in too long. No more than 10-15 minutes is recommended.

    The procedure Geezer mentioned is similar to the General Motors TSB for cleaning a Dex Cool sludged engine except they want it left in much longer. The oxalic should first be dissolved in hot water and then put into the engine. Thereafter the engine is high-idled for three hours before the solution is drained and neutralized. Since I'm not dealing with Dex sludge I usually leave it in for one hour. A light cleaning can be less time but the solution must get hot for it to do any good.


    The following is from GM bulletin #99-06-02-012D. Since it's a very involved procedure I've edited it.

    Cause: Vehicles equipped with DEX-COOL® coolant, which may have been operated for extended periods of time with a low coolant level, usually in excess of 32,000 km (20,000 mi), may be susceptible to the formation of a rust-like material in the cooling system.

    Correction: Flush the cooling system using the repair procedures that follow.

    Parts and equipment required/suggested for this correction:

    • 1 each Prestone® Heavy Duty Cooling System Cleaner, GM P/N 12346500 - 1 per vehicle. This cleaner is in powder form and contains a neutralizer. Do not substitute other cleaners. The diluted cleaners that are available in liquid form are not effective and not recommended for this repair.

    1) Disconnect both coolant hoses to the heater core from the engine.

    2) Back flush the heater core for 5 minutes after clear water is present. Pressurized water not to exceed 345 Kpa (50 psi), may be used.

    3) Reinstall the heater hoses to the engine.

    4) Mix the Prestone® Heavy Duty Cooling System Cleaner, GM P/N 12346500, in approximately 3 L (3 qt) of warm water. Pour the mixture into the radiator. Top off the system with plain water and reinstall the radiator cap. Run the engine at 1600 to 1800 RPM with the air conditioning in the maximum cool position.

    Important: It is imperative that all air pockets have been removed from the cooling system in order for the cleaning procedure to be effective.

    Important: The flushing procedure relies on heat as a catalyst in order to be effective. Ambient temperatures below 10°C (50°F) do not allow sufficient cycling of the thermostat to effectively clean the cooling system.

    5) The cleaner should be left in the system for three hours (after normal operating temperature of the cooling system has been achieved). Normal operating temperature is when the coolant temperature stabilizes around 98°C (200°F). The best results are obtained when the coolant temperature is between 98°C (200°F) and 110°C (230°F). DO NOT EXCEED 113°C (235°F).

    When this temperature has been reached, start the clock. Periodically (every twenty minutes or so), monitor the coolant temperature and engine during the three hour run time. A half hour has been built into the actual labor time to cover for the time spent monitoring the engine, etc. In order to achieve a constant temperature of 98°C (200°F) to 110°C (230°F) during this procedure, maintain the idle speed, turn on the A/C or partially close the hood. (JJ: Or block the radiator)

    6) Turn off the engine. Caution: The cooling system and coolant are hot and under pressure. Loosen only the radiator drain until the pressure has been released from the cooling system and follow the procedures exactly in this bulletin, using normal safety precautions to avoid being injured by the hot coolant mixture.

    7) Drain the radiator and block. When the water has stopped coming out of the radiator drain hose, close the radiator drain. Using Prestone® Heavy Duty Cooling System Cleaner, GM P/N 12346500, mix the neutralizer (from the bottom of the can) with approximately 3 L (3 qt) of warm (shower temperature) water.
    Notice: Do not put cold water into a hot engine as engine damage may occur.

    8) Pour the mixture from the step above into the radiator. Completely refill the cooling system with warm to hot water. When the radiator is full, install the radiator cap to the safety catch. Important: It is imperative that all air pockets have been removed in order for the procedure to be effective. Important: Under no circumstances should the neutralizer be left in the cooling system for any longer than ten minutes once the vehicle has reached operating temperature (thermostat open). The neutralizer is corrosive to aluminum and will damage system components if it is left in the cooling system for longer than ten minutes.

    9) Start the engine and run at high idle. With the A/C on, bring the cooling system back to normal operating temperature and follow the directions on the can.

    10) Allow to cool and drain the system, following the procedure listed above. Back flush for two minutes (or until water runs clear) through the upper radiator hose. Alternately, fill and drain several times until water runs clear.

    11) Close radiator and block drain. Fill with a mix of 50% coolant and distilled water.

  8. #8
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    Default Re: Oxalic acid flush, created something when neutralized..

    I'll have to block the radiator to get temps up. Ac doesnt really have an effect. Almost instantly the build up, or what ever formed dissapeared after adding another 2tb spoon acid dose.

    In the thermo housing, the walls of the metal have taken on a light sea green color. Looks like the metal is colored, not a film or build up.

    I appreciate the input guys, I'll report back after getting temps higher and flushing..

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    Default Re: Oxalic acid flush, created something when neutralized..

    Yeah, get it hot. You could always leave the T stat in. I edited it out but GM states to leave it in and then replace with new after the procedure is done. I kept an old one around for the purpose and so I could drive the car during that hour if I needed to.

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    Default Re: Oxalic acid flush, created something when neutralized..

    Blocking the front of the nose and turning the ac on max allowed me to maintain right at 200*f. Ran it at idle and high idle for 45minutes. Initial draining gave me a reddish tinted water. After adding the base i was able to get most of it out within 10-15 minutes. No blue/green chemical reaction this go round... I'm going to bet it was the larger quantity of base + longer time left in the system that caused the green coating on the copper parts. Apparently adding a base to copper pipes will cause this reaction if an acid is present. I found a book on google that stated this is used before cleaning the cooling system of some sort of generator plant. (not sure if its electric generation)

    fast forward- after 8 drain and fills the water was perfectly clear. I added 50/50 of g-05 and after the first heat cycle it now has the same reddish tint to it. I have some guesses as to what it is but no way to prove it. Has a very similar smell to rust Unless this is hurting the system I plan to run it a few days and drain and refill with water and repeat over the next week until its clear.. The coolant is still transparent, just more orange/red then clean g-05

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