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The piston-cooling valve is normally closed at low en-
gine speed, this to prevent the oil pressure from drop-
ping at low idle. As engine speed increases, the piston-
cooling valve opens to direct the oil to six calibrated
nozzles, one under each piston.
Piston-cooling nozzles
If piston cooling is cut-off, reduced or wrongly aimed,
the piston will seize after a relatively short period under
load. Oil for the piston cooling does not pass through
the oil filters during pressure feed but from the oil tank
via the oil pump and on to the piston cooling nozzles.
Therefore, the greatest possible cleanliness must be
observed in all work connected with the oil tank, suc-
tion lines and suction strainers, likewise the piston
cooling valves, the nozzles and their ducts.
The piston cooling nozzles must never be straight-
ened or repaired in any other way. If damaged or de-
formed, they must be unreservedly replaced with new
ones. Great care should, therefore, always be taken
when working on pistons, connecting rods, cylinder
liners in piston cooling engines so as not to damage the
nozzles.
Clogged piston cooling nozzles must not be cleaned
and re-used, because of the risk of dirt particles being
left in the system. When servicing after piston seizure,
the oil cooling drillings must be blown clean and all
the piston cooling nozzles replaced.
The nozzles aim the oil jets at a carefully selected area
inside the piston, see arrow.
Front main bearing cap
Oil pump
Oil pump
Removing
1.
Remove the starter motor, oil filters, coolant
pump, sump.
2.
Remove the suction and delivery pipes from the oil
pump, the oil pump rear bracket and housing for
the relief valve.
3.
Remove the front main bearing cap together with
the oil pump.
4.
Do not separate the oil pump from the main bear-
ing cap.
Should it happen that the oil pump has been sep-
arated from the main bearing cap, adjust the pump
according to the instructions overleaf.
