The Stovebolt Site Forums The Shop Area Engine Shop acid question

I removed the water pump and poured CLR into the hole letting it run to the back of the block (where the crud is) and left it there 2 days. After that I drained it, neutralized with baking soda dissolved in water, washed out lots of junk, blew air at about 50 or 60 psi when the rinsing water was in there (reverse direction). Caused more crud to come out...some of which was about the size of a bb or smaller. My question: is there a better acid...something that would dissolve the old crud better or should I repeat with the CLR and leave it much longer?
Jon

On really badly clogged radiators like the concrete mixers I used to maintain that got full of cement dust, I used technical grade Hydrochloric acid (Called "Muratic" acid at home improvement stores and swimming pool supply places). It's extremely aggressive, and can open up pinholes in radiators that aren't in the best condition. Pour In 8 ounces or so, fill with water, and run the engine at a fast idle for 30 minutes. Drain, flush with clear water, and add a box of baking soda to the next water fill. Run the soda solution for at least 10 minutes, drain and flush, then fill with a 50/50 antifreeze/water mix.

Litmus paper

Thanks Jerry,
Since the radiator and water pump are out of the engine at this time, do you think muriatic acid would be ok to use? That is to pour the acid or acid/water solution into the water pump opening and let it sit there? If so, what ratio and how long? This engine was from 1959 by the way so it has the larger water pump opening. I'm not certain about the radiator. I had it recored around 1985 and it was only used until around 1997. If I run water in and shake it, a bit of whitish material will come out but at this point I'm more interested in removing as much of the crud in the back of the engine as possible. Water drains out of the block well enough through the back plug opening but I'm certain as much of that junk as possible needs to come out of there.

By the way, when I got this engine the back coolant drain plug was rusted solid in the block. I tried everything to remove it...P'blaster, WD40, Liquid Wrench, etc plus heating/chilling (with ice) and heating and melting wax into the threads. Nothing would move it. So I ended up filing the front of the plug smooth, making a punch mark in the very center and drilling through it using successively larger bits. When I got close to the point where I thought it was prudent to stop so as not to threaten the threads, I took one of those small hacksaw blades and carefully and slowly made two cuts...one at about 6 o'clock and another at about 9 o'clock. With a good light I could see the top of threads on the 6 o'clock cut, so I knew roughly when to stop. Then I smacked that quarter of the circle with a metal chisel and small hammer until it broke loose. After that I tapped the remainder of the plug with the small hammer and it was easy to remove using a pair of common pliers. Then I ran a 1/4 npt tap through to clean out the threads and all is well. Without any doubt it was the most stubborn rusted in plug I've ever seen. I pass this on in case others have this same problem. Also I found Amazon a good source of brass drain screws and other brass fittings. They have some of the old type that the hardware stores and auto parts stores don't carry around here.
Jon

Just to give an idea, on my 1953 235ci, I did remove the side frost plugs and got creative with the garden hose and a long blow gun. I went at it until not much was coming out, plus replacing 60+ years old plugs was a cheap insurance.

Some of the blocks are full of hard black crud which nothing will dissolve and has to be manually broken up to get it out. This is best done when the engine is totally disassembled. My guess is that this stuff it radiator stop-leak put in to stop the radiator from leaking on the farm. Radiators were expensive and farmers were poor. "Put in another can Jeb!" We need to get the rest of the corn in."

Thanks guys. I appreciate the responses. Still I think there must be some acid that would dissolve the stuff. I'm just pouring it in the water pump opening until it reaches the top and letting it run to the back (which from the angle of this engine and length I assume would be about an inch and a half maybe 2 inches deep at the rear of the engine. Since I can not replace that rear plug and since I don't know if was steel nor brass I don't want to threaten it with the wrong acid. The CLR did wash quite a bit of crud out of there. For this purpose I have a nylon barb fitting screwed into the drain hole. Maybe I need to repeat that and leave it for a week or two. Or maybe as Jerry said, muriatic acid is the thing and just pour it in there with no dilution. The side plugs are steel. I can check them easily with a magnet. Thanks again.
Jon

Most tank cleaning kits you can buy use Phosphoric acid. It's weaker but a lot safer than Muriatic acid. It has to sit longer. You can buy gallons of Phosphoric at most home centers.

If a magnet picks up the parts of the drain valve it"s not brass.

Well, I had some strong vinegar here (I don't know if it was 20% or 30%) and I poured it into the water pump opening. It bubbled, fizzed and reacted for about 8 or 9 hours and then stopped. I drained it off and learned it had dissolved quite a bit of crud in there during that time. Apparently after it reacts with rust, crud, etc it sort of neutralizes itself or loses its punch. I didn't expect that, but maybe that is the nature of it. It certainly seemed to open things up, however. I'm going to order some 30% vinegar from Amazon and run some more into the block (undiluted) and also dilute to about 15% and shake it around in the radiator.

If you're interested, please stay tuned. Sooner or later I'm going to figure out what will work the best.
Jon

Something like a pump for a decorative fountain could be plumbed to the drain port to keep the acid bath circulating. The one I use on an old pitcher pump fountain in my yard is all plastic and submersible, and pretty cheap. Even if it wore out or failed within a few days, it might be worthwhile to keep the crud cutter solution in motion.
Jerry

Not tried it, but Evapo-Rust sounds like pretty good stuff for dissolving rust. Might want to check it out.

Dennis

It does dissolve rust slowly. Would be hard to get in all parts of an engine. Not sure, however, if all the problem scale is rust, or some salt that only dissolves in an acid.

Ed

If using Muriatic Acid be careful, if you do it in your garage, everything in there that is bare metal will get rusted from the fumes, and it will also alter your chrome. Use it outside down wind of anything you like. I learned the hard way.

Well after a lot of reading, study and thinking I've decided to pour more CLR in there and leave it for at least a week and maybe two. It did after all break down a lot of the crud and that was in 2 days. Possibly I was too quick to drain it. Maybe in 10 days it will finish the stuff off completely. All other acids I looked into had pretty sincere warnings and the strong vinegar (which worked very well at first) lost potency pretty quickly and then seemed to not be doing much. I'll let you know how it goes. Thanks for everyone's help.
Jon

Phosphoric acid isn't that bad. It's in every Coke & Pepsi you drink.

I know, but the CLR was handy and after all it did work before. As I said, I think I pulled the trigger too fast. We were leaving town and I wasn't comfortable leaving it in there for 8 or 9 days. In retrospect I shouldn't have worried about it. Sad the vinegar lost its punch quickly. I was pretty hopeful that would do the trick. Strong stuff it is. Thanks again.
Jon

Figure out some way to circulate the cleaner, no matter what you choose to use. Just letting it sit there will do little if any good. Either assemble the complete cooling system and use the water pump to move it at normal engine operating temperature (best choice) or rig some sort of pump if you're going to clean only the block. If you dilute the muriatic acid as I suggested, about 4 ounces per gallon of water, fumes won't be a problem.
Jerry

Hi Jerry,
I don't have a pump but I am poking a coat hanger in there a few times a day. I have the tip bent so that I can make it go around the 6th cylinder and I use it to scrape at things. Hopefully that will help. I've thought about looking for a bottle brush I could braze to the coat hanger but haven't seen one I think is stiff enough yet. I need to go to the Chinese Market. There are tons of brushes there. Thought of using a gun cleaning brush but those are not cheap and it definitely would not turn a corner. Besides most of those are brass and aluminum and CLR warns you not to use the product on copper, brass or aluminum. I took one of the larger pieces of what first washed out, put it into an old film canister (nylon) and after about 4 days the CLR reduced what was about the size of a small pea to a gritty dirt-like slurry which will drain out easily. I'm not thinking all of it will come out, but I'm confident a lot will. Once it is back together I'm happy to try your acid treatment or possibly oxalic acid.
Jon

A 110 volt submersible pump for a garden fountain costs six bucks on Ebay. I go through about one a year so my wife's fountain by the front door can trickle water out of an old pitcher pump she found when we bought our farm.
Jerry

Here is what I've learned about CLR, engine block crud and time...

If you need to remove your water pump and use CLR in your block to remove crud at the back it will work. At first I left the CLR in there 2 days before draining and neutralizing it. It removed quite a lot, but it was obvious there was more. Then I tried vinegar (strong) which also worked but seemed to lose its punch after a couple of days and thus was going to be more expensive of a process. Then I poured CLR in there and let it sit for 7 full days. Then I drained it, got a lot more out and neutralized it. I learned something interesting about neutralizing with baking soda and water: if you dissolve about 1/4 box of soda in a gallon of water and use this, you will cause a lot more of the crud to come out. Watching it as well as I could, I can tell the CLR soaked deep into the crud. The baking soda causes the same bubbling reaction that baking soda and vinegar (or any acid) cause and this bubbling action helps remove more junk. Be careful not to pour too much in too quickly. At first it will react and bubble rather violently. I think the reaction causes the crud to break off and into smaller bits where it will flush out easily. The secret seems to be that you must leave the soda/water mix in there for hours, change it and then add some more soda/water. At the end I wasn't getting any more crud out of there, so I'm going to stop, put it back together and try oxalic acid with the engine running later. I would conservatively say I washed enough junk out of the back of that block to fill a beer can. And it could have been one and a half or two beer cans. The vast majority at the end was fine, like black beach sand or volcanic sand and it came out in a slurry.

Another hint: buy a nylon barb fitting (threaded) and attach a rubber tube to this. Stick a bolt in the end to plug it. This will make your work easier.

Hope it helps somebody.
Jon