Hello! I asked myself whether the crankcase ventilation system always consists of normal hose connections for petrol engines. Or is there also the case where valves can be installed there, for example, on the connectors? What sources of fault are there in addition to leaks in such a system? Specifically, I asked myself this with a Citroen C3 from 2003 with 1.4 l machine, since there is the following problem: In the crankcase ventilation hose to the air filter is located si a lot of yellowish smear, which has reduced the hose diameter. Towards air filter, in the air filter itself and direction throttle valve there is also an oily, yellowish substance. It is probably an emulsion of oil and condensation water. Then I wondered if the hose system could be defective. I once took off all 3 connection clips and blown in each connection (yes, is not a delicious matter). Interestingly, for one piece only air in one direction, but hardly in the other. The reason can actually only be a built-in valve?! Could it be that due to a defective valve in the crankcase ventilation system the blow-by-gases are not removed correctly and all, including oil nebulae, in which a hose lands, where they mix with condensate due to the low outside temperatures? Finally a piece of hose was replaced. Could it be that this, because it is a little different nods, which caused problems? Or do you rather tap on e.g. piston rings or valve shaft seals? To the info: – no smear on the oil cover – no visible oil dilution – no oil in the cooling water – No rising bubbles in the cooling water with open balance tank and running engine in idle mode (we had to check it at increased speed) – No noticeable smoke from the exhaust I’m curious about your answers.