Dodge RAM TRUCK 1500 1995 Service Manual page 912

I - S8 5.2L ENGINE
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S Y S T E M
A gear—type positive displacement pump is
mounted at the underside of the rear main bearing
cap. The pump draws oil through the screen and in­
let tube from the sump at the rear of the oil pan. The
oil is driven between the drive and Idler gears and
pump body, then forced through the outlet to the
block. An oil gallery in the block channels the oil to
the inlet side of the M l flow oil filter. After passing
through the filter element, the oil passes from "the
center outlet of the filter through an oil gallery that
channels the oil up to the main gallery which ex­
tends the entire length on the right side of the block.
The oil then goes down to the No. 1 main bearing,
back up to the left side of the block and into the oil
gallery on the left side of the engine.
Galleries extend downward from the main oil gal­
lery to the upper shell of each main bearing. The
crankshaft is drilled internally to pass oil from the
main bearing journals to the connecting rod journals.
Each connecting rod bearing has half a hole in it, oil
passes through the hole when the rods rotate and the
hole lines up, oil is then thrown off as the rod ro­
tates. This oil throwoff lubricates the camshaft lobes,
distributor drive gear, cylinder walls, and piston
pins.
The hydraulic valve tappets receive oil directly
from the main oil gallery. The camshaft bearings re­
ceive oil from the main bearing galleries. The front
camshaft bearing journal passes oil through the cam­
shaft sprocket to the timing chain. Oil drains back to
the oil pan under the number one main bearing cap.
The oil supply for the rocker arms and bridged
pivot assemblies is provided by the hydraulic valve
tappets which pass oil through hollow push rods to a
hole in the corresponding rocker arm. Oil from the
rocker arm lubricates the valve train components.
The oil then passes down through the push rod guide
holes, and the oil drain back passages in the cylinder
head past the valve tappet area, and returns to the
oil pan.
O I L PUMP
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PUMP
PRESSURE
The MINIMUM oil pump pressure is 41.4 kPa (8
psi) at curb idle. The MAXIMUM oil pump pressure
is 207-552 kPa (80-80 psi) at 3,000 EPM or more.
CAUTION If oil pressure Is 2E30 at curb Idle, DO
HOT run engine at 3,000 R P M .
REMOVAL
(1) Remove the oil pan.
(2) Remove the oil pump from rear main bearing
cap,
INSTALLATION
(1) Install oil pump. During Installation slowly ro­
tate pump body to ensure driveshaft-to-pump rotor
shaft engagement.
(2) Hold the oil pump base flush against mating
surface on No.5 main bearing cap. Finger tighten
pump attaching bolts. Tighten attaching bolts to 41
N°m (30 ft. lbs.) torque.
(3) Install the oil pan.
PiSTGN AND CONNECTING ROD ASSEMBLY
The pistons are elliptically turned so that the di­
ameter at the pin boss is less than its diameter
across the thrust face. This allows for expansion un­
der normal operating conditions. Under operating
temperatures, expansion forces the pin bosses away
from each other, causing the piston to assume a more
nearly round shape.
All pistons are machined to the same weight, re­
gardless of size, to maintain piston balance.
The piston pin rotates in the piston only and is re­
tained by the press interference fit of the piston pin
in the connecting rod.
(1) Remove the engine from the vehicle.
(2) Remove the cylinder head.
(3) Remove the oil pan.
(4) Remove top ridge of cylinder bores with a reli­
able ridge reamer before removing pistons from cyl­
inder block. Be sure to keep tops of pistons covered
during this operation.
(5) Be sure the connecting rod and connecting rod
cap are identified with the cylinder number. Remove
connecting rod cap. Install connecting rod bolt guide
set on connecting rod bolts.
(6) Pistons and connecting rods must be removed
from top of cylinder block. When removing piston and
connecting rod assemblies, rotate crankshaft to cen­
ter the connecting rod in the cylinder bore and at
BDC. Be careful not to nick crankshaft journals.
(7) After removal, install bearing cap on the mat­
ing rod.
Check the crankshaft connecting rod journal for ex­
cessive wear, taper and scoring.
Check the cylinder block bore for out-of-round,
taper, scoring and scuffing.
Check the pistons for taper and elliptical shape be­
fore they are fitted into the cylinder bore (Fig. 4).