will be maintained at a value that corresponds with the pressure in the crankcase 11 in this condition the second valve 20 is closed and allows no passage of crankcase gases to the suction pipe 9 via the opening 35 this in turn results in that the pressure in the crankcase 11 increases during this course of events there will be a certain flow of crankcase gases from the third chamber 32 via the restrictor 34 and further on to the suction pipe 9 however the restrictor 34 is so dimensioned that the building up of pressure in the crankcase 11 is not affected to any considerable extent if the pressure in the crankcase 11 should exceed a maximum permissible limiting value the valve device 15 will assume the condition that is shown in fig3 c in this regard the first valve 19 will be influenced towards its closed condition as a consequence of the prevailing high pressure in the crankcase 11 and thus also in the pipe 16 affecting the first diaphragm 21 in a direction in which the valve element 24 a sealingly bears against corresponding opening 25 in this case the pressure in the third chamber 32 will gradually drop towards a value which corresponds to the pressure in the suction pipe 9 due to the fact that gas is allowed to flow to the suction pipe 9 via the restrictor 34 finally the.