Im getting a flow recir error in heat disenfect
I did a pressure test on hydroblock but found no leak, This is a fresenius 2008k machine

Check your dearation motor/pump.If not the dearation check V41 by a valve test in Diagnostics

Make sure the hose in the back of machine for the vent isn't pinched close either.

Actually loboy is correct, the dearatn pumphead is the problem, but the funny thing is, when you test the deaeration pressure, it is OK , but the pump is shot. What gave it away for me was when I put the pressure guage on the dearation pump to test the negative presure, and it was fine, but when I put it in rinse, ( or heat disinfect ) the valve 43 opens as it should, and the pressure went to a positve level...it should go to zero or close to it. Just change the pump head, calibrate the pressure, and try it in heat.. solved my problem everytime.

if the machine has over 20k hours, and your pump and pump head is good, could be the mixing rod in hydroblock is falling apart. Pull dearation oriface out and collect fluid in white drain bucket. If you see small black specks, this could be the problem. I Had a piece break off and plug valve hole on bottom of hydroblock.