Yanmar 3TNV Series Service Manual page 88

Point6
1) Removing pipe seals of 4 valve head.
[Disassemble]
Take off a rocker arm cover in case of 4 valve
head after removing fuel injection pipes and pipe
seals.
[NOTICE]
Attention is necessary because a fuel nozzle is
caught in a pipe seal and the pipe seal is damaged
when a rocker arm cover is lifted with a pipe seal
sticking to the rocker arm cover.
Insert a minus driver in the slit part of the rocker
arm cover, and remove it when removing a pipe
seal.
[Reassemble]
Replace the used pipe seal with a new one when
removing a pipe seal.
2) Breather system (A reductor to intake air system
of blowby gas)
Emitting blowby gas is harmful to natural
environment. Therefore blowby gas reductor is
adopted to TNV series naturally- aspirated engines
as breather system (Turbocharged engines
emitblowby gas).
The system of model 3/4TNV84 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 mixes with splash oil, and
becomes oil mist-blowby gas ith 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.
[Disassemble]
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.
4. Disassembly, Inspection and Reassembly of Engines
73