mannydantyla

I gave my Jeep acid. Oxalic acid, that is.



I put it in the cooling system to etch away all the rust and crud inside the iron block and head's coolant passages which where very badly corroded and causing my engine to slowly overheat.

First, I drained the radiator through the lower hose then reattached it. Mixed the oxalic acid crystals with hot water and poured it into the radiator through the filler neck. The crystals didn't dissolve in the warm water right away though and I had to kinda spoon it all in there.

After driving it around for two days, I drained it and this is what came out:



This time I completely flushed the system and removed the thermostat. The thermostat had a yellowish coating on it. At first I thought the metal was etched by the acid but I could scratch off the coating with a knife.

And this is what the inside of the head's coolant passages looked like after the acid flush:



For comparison, this is what it looked like before the acid flush but after flushing with both Blue Devil and Prestone:



So much better but not squeaky clean.

I'm not sure if I should be concerned about the yellow coating inside there or not - maybe I should have completely flushed all the coolant out instead of only draining the radiator - but when I filled the cooling system back up I put another bottle of Blue Devil flush additive in there with distilled water and now I'm driving it around and will flush that all out today or tomorrow.

Yesterday I drove for about an hour on the interstate and the needle never started creeping up at all! Stayed put right at around 200. (I have a 180 thermostat and will put a 195 in there soon). My problem was that the coolant temp would slowly creep up while driving down the highway until it boiled over. I've replaced the radiator, thermostate (Stant superstat), radiator cap (and tested it first), fan clutch, water pump, and both hoses. Checked for blown head gasket with a combustion leak detection test kit twice and it tested negative.

So, the acid worked!!!

Give your jeeps acid...

dans98xj

Nice idea. What was the mix ratio of Oxalic Acid to water? I just read some stuff about this and it works well just have to neutralize with backing soda and flush again.

mannydantyla

I used the whole 12 ounce container and filled up the cooling system with distilled water

mannydantyla

I flushed the cooling system for hopefully the last time today

Three days ago pure tap water and one bottle of Blue Devil radiator flush. This is what came just now:



So as you can see there was plenty of rust/crud that the flush additive was able to get out after the oxalic acid. It also removed most of the yellow coating:



Not perfect but looking more and more like bare metal

The thermostat before and after the blue devil flush:




And here's the inside of the aluminum thermostat housing, I think the oxalic acid noticeably etched it:



After I put it all back together I hoped in my pickup to get some distilled water and antifreeze but the fuel hose was dry rotted and I spilled half my gas tank in the Oreilly's parking lot. A day working on my trucks is still better than a day in the office though!