Quote:
Originally Posted by keep_hope_alive
Sounds like you have a crankcase ventilation issue, hence the excessive pressure and excessive oil collection in the catch can.
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I agree.
Below is the description of PCV operation for the I4, taken from the repair manual. This system is more complex because of the turbo.
DESCRIPTION AND OPERATION > CRANKCASE VENTILATION SYSTEM
DESCRIPTION > OPERATION
The primary control is through the positive crankcase ventilation (PCV) valve (2) which meters the flow
at a rate depending on intake manifold vacuum. The PCV valve is an integral part of the camshaft cover.
Fresh air is introduced to the engine through PVC (1) under normal operating conditions. If abnormal
operating conditions occur, the system is designed to allow excessive amounts of blow by gases to back
flow through the crankcase vent valve (3) into the intake system to be consumed by normal combustion.
Only on turbocharged engines, there is a one way valve (2) in the camshaft cover in order to prevent the
crankcase from being pressurized by positive pressure in the intake manifold when the turbocharger is in
operation. When the turbocharger is operational, the pressure in the intake manifold can exceed
atmospheric pressure which, without the one way valve, would force oil and PCV gases out of the
camshaft cover and into the induction system, via the hose to the camshaft cover. This can cause
coking of the throttle body and induction system, and can reduce the efficiency of both combustion and
the intercooler system, in normal operation the PCV gases are drawn into the air stream post intercooler
(6). However, when the turbo is spooled up the turbo can become the vacuum source for the vent
system. PVC#4 controls the max. flow so the crankcase stays at a normal vacuum during normal
operating conditions.