Pressurised crank case normal on 204 engine?

[Fluff34567]

Weird one and goes against my engineering logic .. I started the engine recently having forgot to reinstall the oil filler cap. Apart from a rough running engine I noticed a significant pressure coming from the oil filler.

Installing the cap caused the engine to run smoothly.

Anyone want to confirm and start the engine with filler cap removed and see what happens ?

 

[DXX]

It is normal to have some ‘blow-by’ gases, however excessive blow-by will be caused by worn cylinder bores / piston / piston rings.
Get a cylinder compression check by a reputable garage.

 

[Dellmassive]

can you get a video clip of it?

 

[Fluff34567]

No video at the moment as its all apart for the EGR change and the charge cooler cleaning.

 

[Loz]

The crankcase breathes through a pipe and into the air intake; opening the cap provides an easier path for the air.

 

[Mooncat]

Just to expand on the post above, the rough running is due to the air that enters via the oil filler opening being after the Mass Air Flow meter.