I'll tell you my tale of woe about coolant foaming.
I have three machines that have high pressure pumps. My Sharp is one of them. I used Valcool 800 and it foamed. I used Hangsterfers S500cf and it foamed like the dickens. I put in all the antifoam crap and that cured the problem for a day.
Clogged all the filters with the stuff. I called the Hangsterfers rep and he sent me 10 gal of NeoSol 300 for free. That cured the problem.
I spent a lot of time checking PH and hardness of water. Sent in samples to the lab....
Changes to Neosol and the issue went away