View Full Version : How to clean engine block and head water deposits?

12-28-2007, 12:43 PM
Anyone know how to clean out deposits in water jackets of the block and head?

There are some nasty looking deposits in there.. see pics. Looks kind of like the "popcorn" on an acoustic-treated ceiling. I had thought my machinist would know what to do, but he said they don't allow the super-caustic dips anymore that'd clean stuff like that.

Any ideas, or do people just live with it in there nowadays?

One challenge is that I've already had the block bored and honed, although I suppose if it was important enough I could clean the deposits and do it again.


Looking at cylinder through side of block:

View through open plug on end of block:

12-28-2007, 12:57 PM
Muriatic acid works the best. Plug up the holes, fill the block and let soak. Drain, flush, repeat as required. Do the same with the head.
It won't harm any of the machined areas.

12-29-2007, 10:52 AM
Excellent, I'll try that.

- Any tricks to make sure all the crud gets flushed out once it falls off?

- Do you know if the muriatic acid will damage the new engine plugs, or machined surfaces if some spills on that?

Thanks again!

12-29-2007, 11:10 AM
Just lots of flushing with a hose. If you have, or have access to, a power washer, stick the nozzle wherever you can and use that, followed by the hose treatment and compressed air. Most of the crud should be in solution anyway.
The acid shouldn't hurt any of the machined surfaces. It's what I use to remove melted aluminum from cylinder walls after engine boo boos.

12-29-2007, 01:04 PM
ok--I'm here at Osh wondering how much to get. Do you use the stuff 1:1 or dilute it? Bottle says it's 31% Hcl by weight. Thanks.

12-29-2007, 01:34 PM
MT, based on the pictures you posted, I'd get a couple of gallons. Try the first pass at a 50% dilution. If that has little effect, go full strength.
Any leftover makes great concrete cleaner, for the rare spot that shows up under an LBC.

12-29-2007, 02:35 PM
Be sure to get and use an air filtration mask made to absorb the vapors from the acid. Gloves and a full face mask are also a good idea.

12-29-2007, 02:51 PM
Excellent point. I guess that I've had safe working practices drummed into me for so long that sometimes I just assume too much!

12-30-2007, 01:28 PM
Given I want to handle the acid as little as possible, how long of a soak are we talking about--hours, days, weeks?

12-30-2007, 02:33 PM
MT, I'd let the first try sit overnight, but monitor the process. If it still looks as though the solution is working after that period,(bubbling, etc.) let it sit longer. That may be sufficient, or you may have to repeat with fresh.
I understand your concern about handling the stuff no more than nesessary.

03-02-2008, 10:33 PM
Hey bugeye, I'm finally getting around to doing this.

Is there danger in letting it sit *too* long?

It's been sitting several hours and doesn't appear to have really done anything, and I'd like to let it sit all week while I'm away. My wife could check on it to make sure it isn't leaking or something.

03-04-2008, 04:32 PM

My limited experience with muriatic acid is that when first introduced to rusty metal there will be an initial foamy reaction. It appears as effervescence and there should be some rust sediment breaking free. Once the bubbling stops, it is pretty much done.

Drain off the acid solution into a acid resistant container. Rinse the engine block with a solution of baking soda and water to neutralize any of residual muriatic acid solution. After draining of the baking soda solution rinse the block with water. The used acid solution can be neutralized by mixing in the baking soda solution but use care. The reaction will be allot of foaming caused by the release of carbon dioxide from the liquid. Slowly add the baking soda solution so the container doesn't "boil over".

Another caution when working with acid, always add the water to the acid when diluting an acid. The previous advice of gloves, face mask, etc. is also good.

06-03-2008, 11:49 PM
This worked GREAT! Be careful, though, not to drip the excess around since it will stain concrete, and be aware that the fumes will dissolve oil protecting machined surfaces, thus causing them to rust.

So big tip--use the muriatic acid BEFORE you do the machine work. It will save you a trip back to the machinist, as was the case for me.

And I don't think you can leave it in there too long... as others have suggested, overnight seemed to be the point at which it was no longer doing anything, and time for a fresh fill if the deposits still remain. I found 2-3 cycles got it sparkly clean, and my deposits were really bad.