Manifold and Muriatic Acid

[Donchnz]

Manifold Help
I am in the process of completing a total rebuild of my Atomic 4 engine and have used your on line discussions as my guiding light in the rebuild process along with my trusty Moyer rebuild book. Believe me you guys are great, I could never have gotten this far if it wisent for all the articles, thank you all. Uniformity I am almost at the end of the process and I think I might have ruined my manifold, can anyone offer some advice
I have kept the manifold for last, all I had to do was to recondition the inlet and exit ports. The tap required was a half inch pipe thread. The threads came out perfect my problems started when I wanted to clean the dirt and old paint off of the manifold
I remembered hearing about people using muriatic acid deluded to clean the inside of the engine. I placed the manifold in a bucket of muriatic acid used for pool use and deluded the acid by five times, water to acid. The result after fifteen minutes in this solution was a slow bubble action. I removed the manifold out of the acid and placed into a bucket of water to soak and then power washed it clean. It came out clean but it had had a metallic odor and the exhaust ports still had black suit. I wire brushed the outside in preparation for painting. Then I noticed a clear orange looking fluid forming a quarter inch line along the cylinder firing order numbers. I cleaned it off with break cleaner and continued to wire brush.
I Took Sunday off, and when I returned Monday, the clear orange fluid had returned, the remander of manifold looked great except for this strange fluid. The Manifold was completely dry when I finished the first day. I am totally baffled and worried, what happened, I will pressure test this week.
1. Does anyone know what that clear orange fluid is?
2. Was the muriatic acid the wrong thing to use on cast manifold?
3. Did I do long term harm the manifold.
Vince

[David Masury]

You may not have done anything wrong... a few years ago I had a spare engine that the manifold was almost completely blocked... I took the route similar to yours and repeatedly put muriatic acid in the manifold, proded with wire etc until it came clean... then rinsed it very well... then I rinsed it again with baking soda in the water... that was the proocess.

Remember that the cast iron surface is somewhat porus and you may have still some acid in there that is ever so slightly active....I would removed the manifold and try rinsing again with baking soda and water to neutralize the acid...if you have access to a compressor blow out the manifold then re-install with a new gasket... if you are having leaks around the manifold/block joint. check the surfaces, they should be clean. If for some chance they are pitted you can get a gasket material from an automotive supply place that is made for that condition and make a new gasket that will fill the pits and seal the joint... do not over tighten the bolts.

David

[keelcooler]

Sounds like an old freeze crack.

[ILikeRust]

I used muriatic acid right from the big plastic bottle it came in to clean the water passages of my block, head and manifold. I plugged up as many holes as I could, poured the acid in until the casting was as full with acid as I could get it, and then carefully tipped it in different orientations to get the acid to flow around as much as possible.

It foamed up and sizzled and made some vapors and acrid smoke (don't breathe it!! ), and after a while finally settled down.

Here's what it looked like on my manifold:



Once you drain the acid out and give everything a very thorough flushing and rinsing with a lot of fresh water, you really want to be sure the acid is neutralized by then soaking the item in a solution of water and baking soda.

I found that even after I had flushed an item with fresh water, if I hit it with the baking soda solution, I would still get a little fizzing, indicating a lingering presence of acid. And the first time around, I neglected to give the head a baking soda rinse, and the next day, it was covered in a bloom of bright orange surface rust. I gave it another quick acid bath to get rid of that rust, and then rinsed it and neutralized it with baking soda solution, which prevented any further acid attack.

In my experience, that extra step of neutralizing the acid with baking soda solution is important to really kill off any remaining acid.

Now, if you're continuing to get some liquid seeping out of the casting somewhere, I agree with keelcooler that you might have a fine crack somewhere in the casting. The acid would find its way into the crack and then it would be hard to get it out of there, so that later it would slowly dribble out of the crack, leaving orange, rusty stains with it.

[hanleyclifford]

I agree with the suggestion to neutralize that acid with baking soda. The next step should be the pressure test to see if it will hold 20 psi. Then remove the two freeze/expansion plugs and clean the chamber thoroughly, mechanically, and with air pressure. Then either replace the plugs or tap out with 3/4" NPT and install plugs.

[starbrdtck]

The cleaning out of the A4 manifold and water passages

There is a product I use often in the A4s that i work on and it works very well. It is a de-scaling non toxic agent for heat exchangers. The name is maritime descaler.Hope this helps Michael, jenkins marine bullhead city AZ