1998 DODGE RAM 1500 Engine timing

DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - LUBRICATION
CONDITION POSSIBLE CAUSES CORRECTION
OIL LEAKS 1. Gaskets and O-Rings. 1.
(a) Misaligned or damaged. (a) Replace as necessary.
(b) Loose fasteners, broken or
porous metal parts.(b) Tighten fasteners, Repair or
replace metal parts.
2. Crankshaft rear seal 2. Replace as necessary (Refer to 9
- ENGINE/ENGINE BLOCK/
CRANKSHAFT OIL SEAL - REAR -
REMOVAL).
3. Crankshaft seal flange.
Scratched, nicked or grooved.3. Polish or replace crankshaft.
4. Oil pan flange cracked. 4. Replace oil pan (Refer to 9 -
ENGINE/LUBRICATION/OIL PAN -
REMOVAL).
5. Timing chain cover seal,
damaged or misaligned.5. Replace seal (Refer to 9 -
ENGINE/ENGINE BLOCK/
CRANKSHAFT OIL SEAL - FRONT
- REMOVAL).
6. Scratched or damaged vibration
damper hub.6. Polish or replace damper.
OIL PRESSURE DROP 1. Low oil level. 1. Check and correct oil level.
2. Faulty oil pressure sending unit. 2. Replace sending unit (Refer to 9
- ENGINE/LUBRICATION/OIL
PRESSURE SENSOR/SWITCH -
REMOVAL).
3. Low oil pressure. 3. Check oil pump and bearing
clearance.
4. Clogged oil filter. 4. Replace oil filter (Refer to 9 -
ENGINE/LUBRICATION/OIL FILTER
- REMOVAL).
5. Worn oil pump. 5. Replace oil pump (Refer to 9 -
ENGINE/LUBRICATION/OIL PUMP
- REMOVAL).
6. Thin or diluted oil. 6. Change oil and filter.
7. Excessive bearing clearance. 7. Replace as necessary.
8. Oil pump relief valve stuck. 8. Replace oil pump (Refer to 9 -
ENGINE/LUBRICATION/OIL PUMP
- REMOVAL).
9. Oil pick up tube loose, damaged
or clogged.9. Replace as necessary.
DRENGINE - 3.7L 9 - 7
ENGINE - 3.7L (Continued)

CRANKSHAFT
DESCRIPTION SPECIFICATION
Metric Standard
Main Bearing
Journal
Diameter63.488 - 63.512
mm2.4996 - 2.5005
in.
Bearing
Clearance0.002 - 0.034
mm-
Out of Round
(MAX)0.005 mm 0.0002 in.
Taper (MAX) 0.006 mm 0.0004 in.
End Play 0.052 - 0.282
mm0.0021 - 0.0112
in.
End Play (MAX) 0.282 mm 0.0112 in.
Connecting Rod
Journal
Diameter57.908 - 57.892
mm-
Bearing
Clearance0.015 - 0.055 -
Out of Round
(MAX)0.005 mm 0.0002 in.
Taper (MAX) 0.006 mm 0.0002 in.
CAMSHAFT
DESCRIPTION SPECIFICATION
Metric Standard
Bore Diameter 26.02 - 26.04
mm1.0245 - 1.0252
in.
Bearing Journal
Diameter25.975 - 25.995
mm1.0227 - 1.0235
in.
Bearing
Clearance0.025 - 0.065
mm0.001 - 0.0026
in.
Bearing
Clearance
(MAX)0.065 mm 0.0026 in.
End Play .075 - .200 mm 0.003 - 0.0079
in.
End Play (MAX) .200 mm 0.0079 in.
VALVE TIMING
DESCRIPTION SPECIFICATION
Intake
Opens (ATDC) 0.0É
Closes (ATDC) 236É
Duration 236É
Exhaust
Opens (BTDC) 233É
Closes (ATDC) 17É
Duration 250É
Valve Overlap 17É
VALVES
DESCRIPTION SPECIFICATION
Metric Standard
Face Angle 45É - 45.5É
Head Diameter
Intake 48.52 - 48.78
mm1.9103 - 1.9205
in.
Exhaust 36.87 - 37.13
mm1.4516 - 1.4618
in.
Length (Overall)
Intake 113.45 - 114.21
mm4.4666 - 4.4965
in.
Exhaust 114.92 - 115.68
mm4.5244 - 4.5543
in.
Stem Diameter
Intake 6.931 - 6.957
mm0.2729 - 0.2739
in.
Exhaust 6.902 - 6.928
mm0.2717 - 0.2728
in.
Stem-to-Guide
Clearance
Intake 0.018 - 0.069
mm0.0008 - 0.0028
in.
Exhaust 0.047 - 0.098
mm0.0019 - 0.0039
in.
Max. Allowable
Stem-to-Guide
Clearance
(Rocking Method)
Intake 0.069 mm 0.0028 in.
Exhaust 0.098 mm 0.0039 in.
Valve Lift (Zero
Lash)
Intake 12.00 mm () 0.472 in.
Exhaust 10.90 mm 0.4292 in.
9 - 14 ENGINE - 3.7LDR
ENGINE - 3.7L (Continued)

OIL PRESSURE
SPECIFICATION SPECIFICATION
Metric Standard
At Curb Idle
Speed (MIN)*25 kPa 4 psi
@ 3000 rpm 170 - 758 kPa 25 - 110 psi
* CAUTION: If pressure is zero at curb idle, DO
NOT run engine at 3000 rpm.
TORQUE
DESCRIPTION N´m Ft.
Lbs.In.
Lbs.
Camshaft
Non - Oiled Sprocket Bolt 122 90 -
Bearing Cap Bolts 11 - 100
Counterbalance shaft
retaining bolt28 - 250
Timing Chain Cover-Bolts 58 43 -
Connecting Rod Cap-Bolts 27 20 -
PLUS 90É TURN
Bed Plate-Bolts Refer to Procedure
Crankshaft Damper-Bolt 175 130 -
Cylinder Head-Bolts
M11 Bolts Refer To Procedure
M8 Bolts Refer To Procedure
Cylinder Head Cover-Bolts 12 - 105
Exhaust Manifold-Bolts 25 18 -
Exhaust Manifold Heat
Shield-Nuts8-72
Then loosen 45É
DESCRIPTION N´m Ft.
Lbs.In.
Lbs.
Flexplate-Bolts 95 70 -
Engine Mount Bracket to
Block-Bolts61 45 -
Rear Mount to Transmission-
Bolts46 34 -
Generator Mounting-Bolts
M10 Bolts 54 40 -
M8 Bolts 28 - 250
Intake Manifold-Bolts 12 - 105
Refer to Procedure
for Tightening
Sequence
Oil Pan-Bolts 15 - 130
Oil Pan-Drain Plug 34 25 -
Oil Pump-Bolts 28 - 250
Oil Pump Cover-Bolts 12 - 105
Oil Pickup Tube-Bolt and Nut 28 - 250
Oil Dipstick Tube to Engine
Block-Bolt15 - 130
Oil Fill Tube-Bolts 12 - 105
Timing Chain Guide-Bolts 28 - 250
Timing Chain Tensioner Arm 28 - 250
Hydraulic Tensioner-Bolts 28 - 250
Timing Chain Primary
Tensioner-Bolts28 - 250
Timing Drive Idler Sprocket-
Bolt34 25 -
Thermostat Housing-Bolts 12 - 105
Water Pump-Bolts 58 43 -
9 - 16 ENGINE - 3.7LDR
ENGINE - 3.7L (Continued)

²Excessive steam (white smoke) emitting from
exhaust
²Coolant foaming
CYLINDER-TO-CYLINDER LEAKAGE TEST
To determine if an engine cylinder head gasket is
leaking between adjacent cylinders, follow the proce-
dures in Cylinder Compression Pressure Test (Refer
to 9 - ENGINE - DIAGNOSIS AND TESTING). An
engine cylinder head gasket leaking between adja-
cent cylinders will result in approximately a 50 - 70%
reduction in compression pressure.
CYLINDER-TO-WATER JACKET LEAKAGE TEST
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING WITH COOLANT PRES-
SURE CAP REMOVED.
VISUAL TEST METHOD
With the engine cool, remove the coolant pressure
cap. Start the engine and allow it to warm up until
thermostat opens.
If a large combustion/compression pressure leak
exists, bubbles will be visible in the coolant.
COOLING SYSTEM TESTER METHOD
WARNING: WITH COOLING SYSTEM TESTER IN
PLACE, PRESSURE WILL BUILD UP FAST. EXCES-
SIVE PRESSURE BUILT UP, BY CONTINUOUS
ENGINE OPERATION, MUST BE RELEASED TO A
SAFE PRESSURE POINT. NEVER PERMIT PRES-
SURE TO EXCEED 138 kPa (20 psi).
Install Cooling System Tester 7700 or equivalent to
pressure cap neck. Start the engine and observe the
tester's pressure gauge. If gauge pulsates with every
power stroke of a cylinder a combustion pressure
leak is evident.
CHEMICAL TEST METHOD
Combustion leaks into the cooling system can also
be checked by using Bloc-Chek Kit C-3685-A or
equivalent. Perform test following the procedures
supplied with the tool kit.
REMOVAL
(1) Disconnect the negative cable from the battery.
(2) Raise the vehicle on a hoist.
(3) Disconnect the exhaust pipe at the left side
exhaust manifold.
(4) Drain the engine coolant(Refer to 7 - COOL-
ING - STANDARD PROCEDURE).
(5) Lower the vehicle.(6) Remove the intake manifold(Refer to 9 -
ENGINE/MANIFOLDS/INTAKE MANIFOLD -
REMOVAL).
(7) Remove the master cylinder and booster assem-
bly(Refer to 5 - BRAKES/HYDRAULIC/MECHANI-
CAL/POWER BRAKE BOOSTER - REMOVAL).
(8) Remove the cylinder head cover(Refer to 9 -
ENGINE/CYLINDER HEAD/CYLINDER HEAD
COVER(S) - REMOVAL).
(9) Remove the fan shroud and fan blade assem-
bly(Refer to 7 - COOLING/ENGINE/RADIATOR FAN
- REMOVAL).
(10) Remove accessory drive belt(Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(11) Remove the power steering pump and set
aside.
(12) Rotate the crankshaft until the damper tim-
ing mark is aligned with TDC indicator mark (Fig.
5).
(13) Verify the V6 mark on the camshaft sprocket
is at the 12 o'clock position (Fig. 6). Rotate the crank-
shaft one turn if necessary.
(14) Remove the crankshaft damper(Refer to 9 -
ENGINE/ENGINE BLOCK/VIBRATION DAMPER -
REMOVAL).
(15) Remove the timing chain cover(Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - REMOVAL).
Fig. 5 Engine Top Dead Center
1 - TIMING CHAIN COVER
2 - CRANKSHAFT TIMING MARKS
9 - 22 ENGINE - 3.7LDR
CYLINDER HEAD - LEFT (Continued)

(16) Lock the secondary timing chains to the idler
sprocket using Special Tool 8429 Timing Chain Hold-
ing Fixture (Fig. 7).NOTE: Mark the secondary timing chain prior to
removal to aid in installation.
(17) Mark the secondary timing chain, one link on
each side of the V6 mark on the camshaft drive gear.
(18) Remove the left side secondary chain ten-
sioner. Refer to Timing Chain and Sprockets.
(19) Remove the cylinder head access plug (Fig. 8).
Fig. 6 CAMSHAFT SPROCKET V6 MARKS (#1 TDC, Exhaust stroke)
1 - LEFT CYLINDER HEAD2 - RIGHT CYLINDER HEAD
Fig. 7 Using Special Tool 8429
1 - SPECIAL TOOL 8429
2 - CAMSHAFT CHAIN
3 - CRANKSHAFT TIMING GEAR
Fig. 8 Cylinder Head Access Plugs
1 - RIGHT CYLINDER HEAD ACCESS PLUG
2 - LEFT CYLINDER HEAD ACCESS PLUG
DRENGINE - 3.7L 9 - 23
CYLINDER HEAD - LEFT (Continued)

(20) Remove the left side secondary chain
guide(Refer to 9 - ENGINE/VALVE TIMING/TIMING
BELT/CHAIN AND SPROCKETS - REMOVAL).
(21) Remove the retaining bolt and the camshaft
drive gear.
CAUTION: Do not allow the engine to rotate. Severe
damage to the valve train can occur.
CAUTION: Do not overlook the four smaller bolts at
the front of the cylinder head. Do not attempt to
remove the cylinder head without removing these
four bolts.
NOTE: The cylinder head is attached to the cylinder
block with twelve bolts.
(22) Remove the cylinder head retaining bolts.
(23) Remove the cylinder head and gasket. Discard
the gasket.
CAUTION: Do not lay the cylinder head on its gas-
ket sealing surface, due to the design of the cylin-
der head gasket any distortion to the cylinder head
sealing surface may prevent the gasket from prop-
erly sealing resulting in leaks.
INSTALLATION
NOTE: The cylinder head bolts are tightened using
a torque plus angle procedure. The bolts must be
examined BEFORE reuse. If the threads are necked
down the bolts should be replaced.
Necking can be checked by holding a straight edge
against the threads. If all the threads do not contact
the scale, the bolt should be replaced (Fig. 9).CAUTION: When cleaning cylinder head and cylin-
der block surfaces, DO NOT use a metal scraper
because the surfaces could be cut or ground. Use
only a wooden or plastic scraper.
(1) Clean the cylinder head and cylinder block
mating surfaces (Fig. 10).
(2) Position the new cylinder head gasket on the
locating dowels.
CAUTION: When installing cylinder head, use care
not damage the tensioner arm or the guide arm.
(3) Position the cylinder head onto the cylinder
block. Make sure the cylinder head seats fully over
the locating dowels.
NOTE: The four smaller cylinder head mounting
bolts require sealant to be added to them before
installing. Failure to do so may cause leaks.
(4) Lubricate the cylinder head bolt threads with
clean engine oil and install the eight M11 bolts.
(5) Coat the four M8 cylinder head bolts with
MopartLock and Seal Adhesivethen install the
bolts.
NOTE: The cylinder head bolts are tightened using
an angle torque procedure, however, the bolts are
not a torque-to-yield design.
(6) Tighten the bolts in sequence using the follow-
ing steps and torque values:
Fig. 9 Checking Cylinder Head Bolts for Stretching
(Necking)
1 - STRETCHED BOLT
2 - THREADS ARE NOT STRAIGHT ON LINE
3 - THREADS ARE STRAIGHT ON LINE
4 - UNSTRETCHED BOLT
Fig. 10 Proper Tool Usage For Surface Preparation
1 - PLASTIC/WOOD SCRAPER
9 - 24 ENGINE - 3.7LDR
CYLINDER HEAD - LEFT (Continued)

²Step 1: Tighten bolts 1-8, 27 N´m (20 ft. lbs.).
²Step 2: Verify that bolts 1-8, all reached 27 N´m
(20 ft. lbs.), by repeating step 1 without loosening the
bolts. Tighten bolts 9 thru 12 to 14 N´m (10 ft. lbs.).
²Step 3: Tighten bolts 1-8, 90 degrees (Fig. 11).
²Step 4: Tighten bolts 1-8, 90 degrees, again.
Tighten bolts 9-12, 26 N´m (19 ft. lbs.)
(7) Position the secondary chain onto the camshaft
drive gear, making sure one marked chain link is on
either side of the V6 mark on the gear then using
Special Tool 8428 Camshaft Wrench, position the
gear onto the camshaft.
CAUTION: Remove excess oil from camshaft
sprocket retaining bolt before reinstalling bolt. Fail-
ure to do so may cause over-torqueing of bolt
resulting in bolt failure.
(8) Install the camshaft drive gear retaining bolt.
(9) Install the left side secondary chain guide(Re-
fer to 9 - ENGINE/VALVE TIMING/TIMING BELT/
CHAIN AND SPROCKETS - INSTALLATION).
(10) Install the cylinder head access plug.
(11) Re-set and install the left side secondary
chain tensioner(Refer to 9 - ENGINE/VALVE TIM-
ING/TIMING BELT/CHAIN AND SPROCKETS -
INSTALLATION).
(12) Remove Special Tool 8429.
(13) Install the timing chain cover(Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - INSTALLATION).(14) Install the crankshaft damper(Refer to 9 -
ENGINE/ENGINE BLOCK/VIBRATION DAMPER -
INSTALLATION). Tighten damper bolt 175 N´m (130
Ft. Lbs.).
(15) Install the power steering pump.
(16) Install the fan blade assembly and fan shrou-
d(Refer to 7 - COOLING/ENGINE/RADIATOR FAN -
INSTALLATION).
(17) Install the cylinder head cover(Refer to 9 -
ENGINE/CYLINDER HEAD/CYLINDER HEAD
COVER(S) - INSTALLATION).
(18) Install the master cylinder and booster assem-
bly(Refer to 5 - BRAKES/HYDRAULIC/MECHANI-
CAL/POWER BRAKE BOOSTER - INSTALLATION).
(19) Install the intake manifold(Refer to 9 -
ENGINE/MANIFOLDS/INTAKE MANIFOLD -
INSTALLATION).
(20) Refill the cooling system(Refer to 7 - COOL-
ING - STANDARD PROCEDURE).
(21) Raise the vehicle.
(22) Install the exhaust pipe onto the left exhaust
manifold.
(23) Lower the vehicle.
(24) Connect the negative cable to the battery.
(25) Start the engine and check for leaks.
CAMSHAFT(S)
DESCRIPTION
The camshafts consist of powdered metal steel
lobes which are sinter-bonded to a steel tube. Four
bearing journals are machined into the camshaft.
Camshaft end play is controlled by two thrust walls
that border the nose piece journal. Engine oil enters
the hollow camshafts at the third journal and lubri-
cates every intake lobe rocker through a drilled pas-
sage in the intake lobe.
REMOVAL
CAUTION: When the timing chain is removed and
the cylinder heads are still installed, DO NOT force-
fully rotate the camshafts or crankshaft indepen-
dently of each other. Severe valve and/or piston
damage can occur.
CAUTION: When removing the cam sprocket, timing
chains or camshaft, Failure to use Special Tool
8379 will result in hydraulic tensioner ratchet over
extension, requiring timing chain cover removal to
reset the tensioner ratchet.
(1) Remove cylinder head cover(Refer to 9 -
ENGINE/CYLINDER HEAD/CYLINDER HEAD
COVER(S) - REMOVAL).
Fig. 11 Cylinder head Tightening Sequence
* - INDICATES SEALANT ON THREADS
DRENGINE - 3.7L 9 - 25
CYLINDER HEAD - LEFT (Continued)

(2) Set engine to TDC cylinder #1, camshaft
sprocket V6 marks at the 12 o'clock position.
(3) Mark one link on the secondary timing chain
on both sides of the V6 mark on the camshaft
sprocket to aid in installation.
CAUTION: Do not hold or pry on the camshaft tar-
get wheel (Located on the right side camshaft
sprocket) for any reason, Severe damage will occur
to the target wheel resulting in a vehicle no start
condition.
(4) Loosen butDO NOTremove the camshaft
sprocket retaining bolt. Leave the bolt snug against
the sprocket.
NOTE: The timing chain tensioners must be
secured prior to removing the camshaft sprockets.
Failure to secure tensioners will allow the tension-
ers to extend, requiring timing chain cover removal
in order to reset tensioners.
CAUTION: Do not force wedge past the narrowest
point between the chain strands. Damage to the
tensioners may occur.
(5) Position Special Tool 8379 timing chain wedge
between the timing chain strands, tap the tool to
securely wedge the timing chain against the ten-
sioner arm and guide (Fig. 12).(6) Hold the camshaft with Special Tool 8428 Cam-
shaft Wrench, while removing the camshaft sprocket
bolt and sprocket (Fig. 13).
(7) Using Special Tool 8428 Camshaft Wrench,
gently allow the camshaft to rotate 5É clockwise until
the camshaft is in the neutral position (no valve
load).
(8) Starting at the outside working inward, loosen
the camshaft bearing cap retaining bolts 1/2 turn at
a time. Repeat until all load is off the bearing caps.
CAUTION: DO NOT STAMP OR STRIKE THE CAM-
SHAFT BEARING CAPS. SEVERE DAMAGE WILL
OCCUR TO THE BEARING CAPS.
NOTE: When the camshaft is removed the rocker
arms may slide downward, mark the rocker arms
before removing camshaft.
(9) Remove the camshaft bearing caps and the
camshaft.
Fig. 12 SECURING TIMING CHAIN TENSIONERS
USING TIMING CHAIN WEDGE - Typical
1 - SPECIAL TOOL 8379
2 - CAMSHAFT SPROCKET
3 - CAMSHAFT SPROCKET BOLT
4 - CYLINDER HEAD
Fig. 13 Special Tool 8428
1 - Camshaft hole
2 - Special Tool 8428
9 - 26 ENGINE - 3.7LDR
CAMSHAFT(S) (Continued)