simscape thermal liquid source

Hey there,

I got a problem with Simscape. I build up a motor cooling model in Simscape using the thermal and the thermal liquid library. As it turned out when using a volumetric flow source for my cooling liquid source of my cooling cycle I don't get the expected fluid flow as a result . Instead I get a backflow in some pipes of my cooling system. When I use a pressure source to build up my potential for the fluid everything flows as expected. I don't understand this behavior because the formulas of the two types of sources are basically the same and I used used the same values for volumetric flow / pressure differential. So why should it end up in different flows when I used the same values?