Takeuchi TB014 Werkstatt-Handbuch Seite 526

4. Disassembly, inspection and reassembly of engines
Point 6
Breather system (A reductor to intake air system of
blowby gas)
Emitting blowby
environment. Therefore blowby gas reductor is
adopted to TNV series engines as breather system.
The system of model 3TNV76 is shown as a
representative of that breather system in the right
figure. Some of the combustion gas passes through
the clearance between the cylinder and the piston,
piston ring, and flows to the crankcase. This is said as
blowby gas. While it passes into the cylinder head and
the rocker arm cover, the blowby gas mixes with
splash oil, and becomes oil mist-blowby gas. Next, oil
is separated from mist-blowby gas with passing
through the baffle plate inside a rocker arm cover.
And it passes through a diaphragm assy and a intake
manifold, and is reduced in the combustion chamber.
Pressure inside a crankcase is controlled by the
function of the diaphragm assy, and suitable amount
of blowby gas is reduced in intake air system.
[Disassembly]
When a rocker arm cover is taken off, check whether
oil or the like enter the diaphragm space from a small
hole on the side of a diaphragm cover or not without
disassembling the diaphragm.
[NOTICE]
1)When a diaphragm is damaged, pressure control inside the crankcase becomes insufficient, and troubles
occur. When the internal pressure of the crankcase decreases too much due to the damage of a spring,
much blowby gas containing oil is reduced in intake air system, and it may cause the combustion defect
by the early dirt of the intake valve or the urgent rotation of the engine by the oil burning.
When pressure progresses in the crank case too much due to the wrong operation of the diaphragm and
so on, it is considered that oil leakage from the joint of a oil pan, a oil seal and so on will occur. When a
diaphragm is damaged, blowby is discharged from the breathing hole on the side of diaphragm cover, and
not reduced in the intake manifold. Therefore, be careful of the diaphragm trouble.
2)At lube oil replacement or lube oil supply
The amount of lube oil isn't to be beyond the standard upper limit (in the engine horizontality, the upper
limit mark of the dip stick). Since the blowby gas reductor is adopted, be careful that the amount of oil mist
may be inducted in the combustion chamber and the oil hammer sometimes may occur, when the lube oil
quantity is beyond the upper limit or an engine is operated beyond the allowable maximum angle of an
engine.
[Reassembly]
Replace the diaphragm with new one, when it is damaged.
gas is harmful to
Diaphragm cover
Spring
Center plate
natural
Diaphragm
Breather baffle
Baffle plate
Breather system componert
61
Rocker arm cover
Intake maniforld
Blowby gas
Diaphragm
Spring
Diaphragm cover
Baffle plate
Rocker arm
cover
Cylinder head
Blowby gas flow