Fig. 4.128. Scheme of system of ventilation of a case of the engine: And — clean air; In — mix of clean air with crankcase gases; With — crankcase gases; 1 — an airintaking hose; 2 — an airintaking branch pipe; 3 — the case of the air filter; 4 — sealing laying; 5 — a cover of the air filter; 6 — the filtering element; 7 and 10 — hoses; 8 — a latch; 9 — the calibrated opening in the case of butterfly valves of the carburetor; 11 — a maslootrazhatel; 12 — a cover of valves

The system of ventilation of a case (fig. 4.128) — closed compulsory, works due to depression in an inlet pipe. The oil separator 11 is placed in a cover of 12 valves.

During the operation of the engine idling and small loadings gases from a case are sucked away through a small branch on a hose 10 and the calibrated opening 9 in the case of butterfly valves of the carburetor. On full loadings ventilation is carried out on a hose 7 in the air filter, on other modes — via the air filter and a small branch.

At operation do not break tightness of system of ventilation and do not allow operation of the engine at an open maslozalivny mouth. It causes the increased carrying out of oil with crankcase gases.

Work of system of ventilation of a case can be checked as follows: during the operation of the engine at the minimum frequency of rotation of a bent shaft idling there has to be a depression in an engine case. It decides on the help of the water piezometer connected to an engine case through a branch pipe under маслощуп. If the system works abnormally, then in a case there will be pressure. It is possible in case of coking up of channels of ventilation or excessive break of gases in an engine case.

At interseasonal service of system of ventilation, at a run of 40 thousand km it is recommended: to uncover valves and ventilation hoses; to clear of resinous deposits a cover oil separator, hoses of ventilation and channels in the carburetor.