Crankcase Pressure / Turbos

Keith Browning · January 28, 2016

I could swear I recall somebody mentioning that they had a leaking 6.4L kick their ass and discovered high crankcase pressure pushing oil out of crank seals but it was not caused by the bottom end... pressure blowing through the turbo oil drain. I have someone reaching out to me so I don't have the truck or any other info. Compression is good supposedly.

Anyone?

Bueller?

Matt Saunoras · January 29, 2016

A few years ago I had a 6.4 with an aftermarket crankcase vent canister installed. It was restricted and the pressure buildup in the engine eventually blew out the high pressure turbo compressor seal and caused the engine to ingest a bunch of its oil. The intake manifold was soaked and the pistons/heads had severe carbon built up.

I have also seen a few 6.4s with high crankcase pressure that drops substantially when the cac tubes are disconnected. I believe the theory is that the high pressure turbo compressor seal can leak boost into the crankcase. There is really nothing stopping boost from flowing into the crankcase once it is past the seal and since the air is compressed within the housing this is possible.

I would think a 6.4 turbo that leaks boost into the crankcase is also going to be leaking oil into the intake when the turbos are not boosting. Thick black sludge in the compressor outlet would tell the story.