Block and Head internal descaling

69.5Mav

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Found this while looking up the chevy 261. Thought others might find it of interrest. It is old so brand names may no longer be available.


Block and Head internal descaling
Professional cooling system de-scaling is done with Sulphamic acid for hard water, lime and antifreeze build up. Oxalic acid is used to remove rust.
Sulphamic acid crystals are available at the hardware store in form of 'grout and tile cleaner'.
Oxalic acid crystals are available in form of 'wood bleach'.
Containers say what acid is used and its pure acid crystals with no other additives.
Available in 16oz. containers, which gives the right mixing ratio with water for the typical carrand names may no longer be available cooling system with 3-4 gallons capacity.

Properly diluted, both acids are just as mild and safe as vinegar (acetic acid) and citric acid, but are more effective and cost is the same.
These treatments are safe to use with copper/brass radiators.
It is supposed to be safe with aluminum radiators as well, but I would do some tests first to determine how much reaction time is actually safe.

Oxalic acid used to be sold as a heavy duty 2-part cooling system cleaner over the counter until a few years ago. Recommendation said to do this annually...

For best results it's essential to keep temperature at engine operating temp and to keep the flow going.
Instructions are to drain and flush first, then fill with the diluted acid mix and run the engine at fast idle for 3 hours.
Do one acid treatment at a time, starting with the sulphamic acid, then drain and flush, followed by oxalic acid, then drain and flush.
The final step is to neutralize any remaining acid with a mix of washing soda and water and run the engine again for a while, then drain and flush and finally fill with coolant, but using distilled water instead of tap water, this time.

These methods really work exceptionally well.
I did both, back to back, on my old engine that had serious scale and rust build up.
Before the treatments and despite a new 3 core radiator, coolant temps easily climbed above 180 during the hot summer months with harder use.
After the treatments, the same engine now needs the thermostat to even get up to 180 degrees, even in the summer.



General Rust and Scale removal
I have used the electrolytic method many times and it works well, but is limited to the rusted areas that are directly exposed to the sacrificial steel.

I also like Oxalic Acid crystals to remove rust, especially for areas hard to reach.
Hardware stores carry it in pure form as 'Wood Bleach' in 12oz containers.
Mix 3-4oz per gallon of water.
'Barkeeper's friend' is mostly fine abrasives with only a small amount of those crystals.

Oxalic acid is still considered a mild acid, but more effective against rust, than vinegar, molasses or citric acid. It's also mild enough to be safe with softer metals, like brass, copper, etc.
You can accelerate the rust removal process with heat and agitation.
Keep the acid hot and stir the rusted parts around in the acid or keep flowing the acid around the parts.

Works excellent for descaling and rust-removal of coolant passages and radiators and was available over the counter until a few years ago, for just that purpose, offered by Prestone.

For smaller parts and when I need instant results, I use Muriatic Acid (Concrete or Pool cleaner), also available in hardware stores. Its 30% diluted HCL, which is aggressive and will eat metal if exposed too long.
Be very careful when using HCL ! Even with this diluted concentration, take all safety precautions for working with harmful chemicals and ONLY work outside, as just the fumes alone will corrode bare metal in its vicinity.
 
that's a lot of good info there that can be applied to carburetors and all kinda of car parts. that was the old general motors radiator flush before epa ( trisodium phosphate and oxilic acid. I've used it with good success but only run it before a tear down because you don't want it left in your engine or on gaskets.

thanks for sharing!
 
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