Worst case of a high pressure in the crank case I have heard of was caused by blow by at the valve stems and cylinder liners. The real cause was that the engine was "dusted" due to not securing the air intake and air got into the engine with out going through the air filter. Dust "sanded" and increased all the tolerances causing pressure in the crank case. The dirty air also "ate up" the turbo blades. This was on a brand new coach that came from the factory with the loose air intake hose. A big problem that no one wanted to stand behind as it was a "maintenance issue". It was finally resolved and fixed but was a real mess. Suggest you do whatever you must to get the problem identified and resolved. The bill to fix the one I know about was about $30,000.
