Lemon juice should be fine, it will darken the aluminum in time. I use a blend of lemon juice and dish soap in my ultrasonic cleaner for aluminum and zinc castings.

Also both Phosphoric acid and Chromic acid can be used on aluminum. The Chromic can be blended with 10% Sulphuric acid.
One may need to watch the radiators with plastic tanks, I have not payed any attention to what will harm the gasket or plastics. I know Sulphuric acid will harden up Nylon.

Then back flush with water to try and clear as much crap out the top as you can get.

I understand about not using it with alum. but with copper, how much mixed in water?

I wonder how well CLR or Lime-away would work? Isn't that pretty much what is built up inside the radiator anyway? Lime, calcium and rust.

Sounds like it should work, but when I've used it on shower heads etc. it was full strength, unless it works as good diluted, I don't think you want to get enough to fill a radiator. Muriatic acid sounds good but how much to use in water is what I'd like to know.

Actually,plain white vinegar and baking soda will boil out shower head deposits...A radiator,who knows?

<< but with copper, how much mixed in water? >>

I just put some water in with the hose & then poured the muriatic in straight from the jug, then a bit more water.

SAFETY SAFETY SAFETY !!!!!

Ed

An old saying.......DO LIKE YOU OUGHTA,POUR ACID IN TO WATER...not the other way around.....KaBoom,sometimes.

I agree, when working with these acids you use them strong, as they come to you. Make sure you understand what these acids can do to your body and pay plenty of respect to them. Some of these acids even diluted can cause you great harm.
But also you soda drinkers. Do you like a pop drink that has a refreshing bite to it? Read the label. You will find Phosphoric acid in the drink, not as much as used to be in there. You can not clean parts with a can of coke as when some of us were young. At a very weak dilution these acids are not nasty but you must understand them.
Keep a large source of water close by as well as a hose to rinse with. I like a pail or a cat litter box full of water to submerge or splash water instantly. Just having a hose nearby is not enough if you splash your face and it starts dribbling around your safety goggles. I want water instantly that takes no manipulation to get into.

With the proper safety procedures you can get into all sorts of stupidly strong cleaners to get tough jobs done.

But keep in mind, if you get into hydrofluoric acid. It really doesn't hurt your skin, it is a fast acting penetrator that it eats your bones away. Research what you are getting into if you are going beyond the over the counter cleaners.

What are the original factory radiators made from? I know my header is made of brass but what is the core made of? I was thinking of going to get some muriatic acid tonight after work but if it is aluminum I may not.

Brass tanks will be all brass copper construction. There may be exceptions. I have not seen any aluminum & brass radiators.
Plastic tanks will generally be aluminum core but there are copper plastic out there.


With a factory Montero radiator you should be safe with Muriatic.