Sump or Oil Pan (Automobile)

3.2.

Sump or Oil Pan

The sump (Fig. 3.18) is attached to the bottom of the cylinder block underneath the
crankcase. The functions of the sump are
(a) to store the engine’s lubrication oil for circulation within the lubrication system;
(b) to collect the oil draining from the sides of the crankcase walls and if ejected directly
from the journal bearings;
(c) to provide a centralized storage area for any contaminants like liquid fuel, water,
combustion products blown past the piston ring, and worn metal particles ;
(d) to provide a short recovery period for the hot churned-up and possibly aerated oil before
it is re-circulated in the lubrication system; and
(e) to provide some inter-cooling between the hot oil inside and the air steam outside.
The sump (Fig. 3.18) may be made from a single sheet-steel pressing or it may be an
aluminium-alloy casting with cooling fins and strengthening ribs. Both the constructions have
a flanged joint face, which matches with a corresponding joint face on the underside of the
crankcase. A soft flexible gasket is used in between to seal the joint and is tightened down by
set-screws. The sump generally has a shallow downward slope at one end, which changes into
a relatively deep but narrow-walled reservoir at the other end. The incoming oil flows towards
the deep end, where it submerges the pick-up pipe and strainer of the lubricating system. A
drain plug is located at the lowest level in the sump for easy drainage of used oil. Generally the
sump is not designed to add to crankcase rigidity, except in some transverse front-wheel-drive
engines.


Cast aluminium alloy sump dissipate heat much better than pressed steel sumps, and it
does not promote resonant (vibration) noise specifically when it has strengthened ribs on the
outside. On the other hand, the pressed-steel sump can withstand impact load without any
serious damage, but the cast structure does not take any impact and can crack.
The oil pan.
Fig. 3.18. The oil pan.
Sometimes baffle plates are used inside the sump to stop oil surge due to bouncing, rolling,
and pitching of the vehicle, or to guide and prevent splashing about of oil escaping from the
journals and bearings of both the crankshaft and the camshaft. Also, a horizontal sheet
supported in a steel frame is installed just below the sump flange joint to strain out draining
contaminants generated by combustion-gas blow-by and to minimize oil splashing.

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