Manifold Acid Cleaning

[dthibaul]

Due to a pin hole leak in the in-line exhaust entry fitting I have removed the exhaust manifold and would like to clean/paint before reinstalling. Is there any reason why I can't just soak it in muriatic acid for cleaning? Full-strength or diluted? Any other suggestions?

Thanks.

[hanleyclifford]

Soaking in muriatic acid is not likely to give you the best result unless it is followed by a vigorous mechanical cleaning using wire thru the holes and blasting with air pressure. The muriatic acid alone will loosen the crud in the jacket but probably leave the junk in position to later be sent downstream to clog fittings and passages or even a pump in the case of fresh water cooling. First prize is to remove all fittings and the two expansion plugs so that you can be sure all loosened crud is not only dislodged but also ejected. If insufficient landing material remains under the expansion plug holes they can be tapped with 3/4" NPT and a plug installed.

[Al Schober]

Muriatic Acid

Your muriatic acid probably has to be diluted. The stuff I buy is 20%, and I don't like to use it at more than 10% - so I dilute 1:1. The ratio will be different if your source is 15% - check the label on the jug.
Soaking really doesn't do it for me - you really need to circulate the stuff. I use one of those pumps that attach to an electric drill. Take a suction on a plastic bucket, and route your return line back to the bucket. A 'sock' of panty hose will catch the big lumps in the return line.
Since you'll want to neutralize the acid before discard, don't use any more than you really need. I neutralize with baking soda and check with litmus paper before discard.
Need I say 'Work Safe'? Safety glasses (with side shields) and nitrile gloves.