Oil coming out of cam cover breather

[tony2311]

My nephew overfill the engine by a litre of engine oil and ran it for over 500miles. :zx11:, He only told me when oil was coming out though the cam breather into air filter and a oil leak, i have change the oil, clean up the air box and throttle, The crank case breather was full of mayo, i clean the pipe up but cant get the plastic box mounted of the engine off to clean it.
Oil is still coming from the cam cover breather into airbox it will stop if i take the oil cap off, the car runs fine, no fault code, idle smooth, So whats causing it?

[SammoVWT]

It may be residual oil in the breather system, i guess taking the oil cap gives it a new way to let the pressure out of the crank case

[tony2311]

The intake system was all clean up, oil is coming from the pipe on the cam cover itself

[martin1810]

The one way valve in the breather is probably not working so pressure is building up in the top of the engine.

[tony2311]

where is the one way valve, the engine is a 1.4 8v 2001

[martin1810]

I am not sure with that engine. If you pull the beather pipe off the cam cover, does the engine breath ok through the breather hole. If it des the valve wil be in the pipework somewhere. Keep blowing through pipes until you find something that restricts air flow.