On Wed, 12 Feb 2014 20:32:23 -0500, micky
wrote:

I've pressure washed running engines for decades and NEVER cracked a
manifold

Do you try to not get the manifold wet?

Why bother? Like I mentioned earlier, spraying a running engine has
never cracked a manifold, head, block or other parts of an engine.

Engine cleaners work best on a hot running engine.