Cleaning engine block


Daily Driver
I have a current interest in this subject;
block 2.jpg

The 2 liter engine I'm building apparently sat for a long while with water in it, but not closed, so evaporation (I think) made it worse. I need to clean it out.


True Classic
I have a current interest in this subject
Yikes, that's nasty.
By the way, I realized I was thinking of someone else earlier when I asked for your input on chemicals. Another of our members is some type of chemical engineer and has offered excellent info on prior discussions. And I was thinking that was you...sorry for the mix up.
I'd be thinking lye for a block with that much build up. Are there still any hot tanks being used in your area? I know they have been banned in CA and NV. If you want to try it yourself, you'll have to do some research to determine the right way to use it. Be safe, follow standard protocol for working with caustic agents.

One problem I considered when thinking about cleaning the coolant passages on a aluminum head was how to keep the passages full of the cleaning agent. The internal passages (head or block) are like underground caves traveling in/out, up/down, around partitions, etc. Difficult to fill all cavities, avoid air pockets, and keep it from leaking out other ports.


Daily Driver
Yikes, that's nasty
I think I can put the water pump back on and only have a little to close; the engine block's already on a stand and fairly level, so I could fill it almost to the top with something and soak it a while- though that won't necessarily clean at the bottom without circulation or movement of some sort.

Simon Oaten

Daily Driver
couple of other things to think abt:

1. are the deck / bores in good condition - and any cleaning agent shouldn't affect these surfaces
2. as steve mentioned - making sure the aux shaft bearings are "eaten" tis important ......

oxlaic acid - does work ok - but leaves a "coating"

and you need to immerse the part for a period of time (4-10 hrs depending upon temp / degree of corrosion etc etc). - think big plastic rubbish bin!

I tape-up the deck/bores, and use conc hydrochloric acid and paint brushes, and then multiple rinses. one has to ensure appropriate PPE, and then dry machined surfaces incld all bolt holes / spray with protective coating (wd40 etc).

it normally takes 2 or 3 goes to get water galleries "clean" with no surface coating ......and no probs (with care) of aux shaft / deck / bores....

acid is dangerous - so gloves / eyes / air need to be taken care of ......

disposal of diluted acid should also be considered .......



True Classic
Some progress, today I take some time and tried with sulfuric acid ( for home 19% ) to wash water galeries, before work I closed on side with metal covers and cut from wood plate for close water pump hole, then all bolt on and pour in around 1.5 liter on acid, from time to time I add to refill up to top, after around 1 hour remove acid and wash with water then I add mixture of water and soda to neutralize, after all it was very good cleaning option and cheap.
Some small corrosion was left and I think that will try once again same process over weekend to get clean as new.
Will later or tomorrow upload few photos.

How to protect water galeries after all cleaning until engine will not run? Any suggestion guys?


True Classic
Nice report, thank you Andreav.

Sulfuric acid will work, but be careful as it can also work too good...meaning it will eat the metal also. I would definitely not try it on the aluminum head. The strength (19% seems a fairly weak dilution) and length of time it is allowed to sit (one hour would be the longest I'd try at first) will make a big difference in how much material is eaten (good and bad). So what you did sounds about right. Better to leave a bit of rust remaining than to damage your block. And neutralizing is vital (you might even consider doing that step twice).

With cast iron it will begin to flash rust immediately after exposing the fresh metal, especially when the water flush and neutralization are done. There are some rust preventatives that you could fill the cavities with, but the typical commercial ones are rather expensive. One possibility is to use Phosphoric Acid; it leaves a phosphate coating as it removes the rust (a chemical consequence of the conversion process). That coating is a good rust preventative. It is much weaker than Sulfuric Acid (although the dilution strength of either can be adjusted to be about equal), so it will need to be a higher % and it will take longer. However that means it is also safer on the metal. It still requires a flush and neutralization, but the phosphate layer should prevent the flash rust from forming for several days to a couple of months (depending on the conditions).

Or you can fill it immediately with "anti-freeze" (engine coolant). It has anti-corrosion agents that will slow down the rust process. It might be tempting to fill it with some type of oil or other petroleum product. But I would not recommend that; it can contaminate the cooling system by coating the walls of everything with what is essentially an insulation layer, making the system less effective at cooling your engine.

For the most part it is impossible to completely prevent any rust from happening. Basically what you are doing is removing the previously accumulated build up of rust and starting the clock over (which will be good for many more years again).

Do you happen to have any pictures of the process or the result? Thanks Andreav.


True Classic
Here are few photos below, thank you on explanation Jeff, you can call me Andrea, Andreav is nickname and it is name and first letter from surname.

Do you think that maybe second time I tried with phosphoric, I have also bought 3 liters of phosphoric acid but I didnt be secure if coating will be problem inside on block.
By that over weekend will try with phosphoric and then neutralising, coat and maybe after to spray light coat of antifreeze will be good and will stop corrosion for some time, until engine is not assembled?
It is like black coating? Will be safe this to run later in engine with anti-freeze?
Phosphoric acid what have is 3x % but dont cook on metal like sulfuric acid.

Please can you confirm me after neutralising with soda, I need to wash all with clean water and dry?



True Classic
Nice job. Looking at the pictures, it seems some areas worked very well but others not as much. Were you able to fill all areas with the acid? I am wondering if that may be why it did not clean as well in places? But it looks good.

If you have phosphoric acid you can try it. Maybe try to position the block so the acid has more contact in the areas that were not completely cleaned the first time. 30'ish percent is fine, I've used 40% and it was safe on the metal (for rusty gas tanks). When the rust is really bad it is faster to use a stronger acid first, then the phosphoric to treat it. The phosphate coating it leaves is actually not a "coating" but the surface of the metal as the rust is chemically converted. So it will not interfere with the cooling system like some coatings can. It is a light grey to dark grey (almost black) color. The amount of rust that was treated will determine the color; worse rust leaves a darker color (more chemical reaction).

After treating with acid I rinse with lots of water first. Then neutralize with soda. If it looks like a lot of the soda is left behind, then maybe flush again with water. But a small trace of soda will not hurt. If you can dry the treated area thoroughly then I would not bother with putting antifreeze until it is ready for use. Putting a little may actually leave more water than protection. Filling the block's passages with antifreeze (and keeping it full) will help more, but that is difficult to do. Even if a little rust forms before you can assemble the engine it should be ok. It will form inside the engine after the cooling system is filled anyway. Really no way to completely stop it from happening.

That block has oil squirters? Uno Turbo or Punto GT?
Sorry for my confusion on your name.


True Classic
Here are explanation about photos, I think it was cleaned very well. Firts photo is showing real condition after cleaning and was properly dry off with compressed air.
Second photo is same as first but there was left some water or just humid place which was after some time left surface corrosion.
Third photo is hard to say but I think, like on second and third photo is layer of paint, grey paint from outside, do you think this is possible? That factory paint or with mistake paint some of insde on water galeries?
I have fill block up to max, to deck and was positioned that there is equal acid everywhere.
Okay I will try over weekend another shoot with phosphoric acid and hope that this will finish work fantastic and will again upload photos.

Okay after neutralising with soday best will be to dry not again risne with water?
In first attempt I have after soda fill with water all, probably not good? But I didnt prepare on time liquid with soda and there was some soda what was not melt in water fully because I use water.

After all cleaning it is on schedule trial assembling to meassure CR and adjust on 10-10.5 then again all on beggining, painting outisde of engne block and then slowly assembling of engine.

Yes block have oil squirters, it is 1600 Tipo block, but if someone will be interested in oil squirters as retrofiting, I will have soon them separately, new made.


True Classic
Third photo is hard to say but I think, like on second and third photo is layer of paint, grey paint from outside, do you think this is possible?
That was the photo that I was referring to as less successful than the rest. But now I understand it may be for other reasons. Unfortunately it may not be possible to clean everything perfectly, just the nature of these things I guess. But more important is overall you have got most of the inside of the block very clean with a good job and it will be fine.

When I flush after the acid, it is first with only water, running for awhile through the system (like water flowing from a garden hose). That is to rinse out as much acid as possible. Then I mix the soda in clean water (like in a bucket) and fill the system. Let that soak for a while to neutralize any remaining acid. Then if it looks like much soda settled and dried inside, I will flush again with just water (same like before with the hose). So no matter how you do it there will be water remaining inside. No way to avoid that. If you can dry out all of that water then there will be less rust (like comparing your first and second photos). But it may be difficult to get all of the water out, so some light rust may form (like the second photo). I think it is the best than can be done, and not enough to be any problems. Most important is it is much better than before.

It will be interesting to see what you get with using phosphoric acid next. But it is not necessary in my opinion, I think what you now have is good. If you have some and decide to try, I will be interested to see photos to compare with the current ones. I have not done this to a block, but with many other parts so I am following your project.

Another good cleaning chemical for cooling systems is Oxalic acid. It is very mild and more for a complete cooling system "flush" to generally clean it (great for radiators). It will not remove the heavy scale but will get rid of most rust and normal accumulation. Many of the good cooling system flush products in the past were Oxalic acid, until our government decided it should not be dumped on the ground so stopped it. But you can still get plain Oxalic acid and make your own flush. It comes as a powder that is mixed in water and run through the system for about an hour. Then rinsed with water, and finally neutralized with soda mix (mosty to protect soft materials like hoses). But if are starting with everything new (clean block, new radiator, etc), then this isn't necessary.

Regarding oil squirters. I would like to hear more about what you can do for a retrofit. Feel free to contact me by email (same address as before) or by message here. Thanks.