turbo boost pressure getting into base oil

[grafexcavating]

My 2006 granite with a 370 410 maxidine motor has been pushing turbo boost pressure into the return oil line on turbo then causing oil to be pushed out blow by tube which makes a huge mess down the side of truck. I have put two Mack remanufactured turbo on truck, then went to a local rebuilder for the third one. The truck now will occasionally does the dirty boost failure once and awhile. It seems to do it under long heavy pulls under max boost. I did have the cam changed early in its life to a non emission cam because this engine out of factory was a dog at low rpm. Cam change fixed that problem. Not sure if this is contributing to this turbo oil seal problem. Has anyone experienced this problem?

[turckster]

Are you sure the turbo oil return is the issue? I had overhauled a Cummins M11, the customer returned within a week with the right side of the engine covered in oil. Under a load and a hard pull it would push the dipstick out of the tube and push engine oil out of the dipstick tube. Eventually found the valve guides were moving up/down with the valves causing boost to come into the crankcase. It was a reman Cummins head BTW.

I have never seen turbo seals cause what you are experiencing, not saying it hasn't happened, just never seen it. I've seen many things cause excessive crankcase pressure but not bad turbo seals, especially seeing the same issue with multiple turbos. I'd look for excessively worn guides, cylinders, bad/down cylinder, etc.

[theakerstwo]

With cat and DD engine this is a common problem and I remember one mack years ago same way.The brg has to be bad for pressure to pass by.Also a air compressor will do same thing.I have seen engine overhaul due to excess crank pressure due to a bad air compress two times.I have seen a few turbos that has blown up and metal lodged in oil return tube.New turbo is install with the return pluged and now oil floods the exhaust thru the seals.