Crankcase ventilation system (oil trap) clogging is a common cause of oil leaks and running problems. When the system is clean, internal engine pressure stays controlled and idle smooths out.

Oil leaks from seals and gaskets (excessive pressure pushes oil out). Rough idle. Oily intake manifold or air filter housing.

Required spare parts: Crankcase vent box (oil trap) O-ring seal. Intake manifold gasket (recommended to change if intake manifold is removed). Throttle valve gasket (if you also clean the throttle valve). Required tools: Socket set (10, 12, 13 mm) and ratchet with extensions. Combination wrenches (13 mm and 21 mm). Slotted screwdrivers (small and large).

Crankcase vent box cleaning is possible with the intake manifold in place, but removing the manifold is highly recommended. It provides significantly more working space and allows thorough cleaning of the idle control motor and throttle.

Hoses and connectors: Remove the crankcase ventilation hoses (pipe from box to intake manifold or turbo). Idle control motor: Remove 10 mm bolts, green connector at rear, and air hoses. Intake pipes: Remove the boost pipe or accordion hose to the throttle. Throttle valve: Remove throttle valve connector and 3 pcs 12 mm nuts. Remove throttle cable rod. Intake manifold: Open 8 pcs 13 mm bolts on intake manifold. Also remove intake manifold support and alternator ground point (12 mm). Electrical and sensors: Remove engine temperature sensor connector (white) from rear of cover and any electrical wire clips (10 mm).

If your car has an EGR system (exhaust gas recirculation), expect longer working time. The EGR valve and its pipes are often in the way, and their removal and cleaning is laborious. In EGR-free models, maintenance is much faster (approx. 2 hours).

Oil trap (crankcase vent box): Wash the box with solvent from inside until no more black sludge comes out. Make sure the channels inside the box are open. Idle control motor: Clean with carburetor cleaner or equivalent so the slider inside moves easily. Throttle valve: Clean the edges and body of the throttle from carbon.

Replace new gaskets and O-ring. Make sure the crankcase vent box gasket sits properly against the block to avoid oil leaks after service. Tighten intake manifold bolts evenly.