Thought this might help a bit. Some comments on descaling from: http://www.siegmundguitars.com/Techtips.html

[b]Block and Head internal descaling[/b]

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 car 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.

Cheers,
Fraser


Cheers,
Fraser

1950 Chevrolet 1300 1/2 ton (Built in Oshawa)

http://1950Chevy.blogspot.com