Dodge Nitro. Manual — part 103

2. If valves or seats have been reground, check valve tip height (A). See Fig. 152. If valve tip height is

greater than 43.65 mm (1.7185 in.) intake or 46.48 mm (1.8299 in.) exhaust, grind valve tip until within
specifications. Make sure measurement is taken from cylinder head surface to the top of valve stem.

3. Install new valve stem seals.

4. Install valve springs. See INSTALLATION.

5. Install cylinder head(s). See INSTALLATION.

ROCKER ARM SHAFT/ROCKER ARM/LASH ADJUSTER

DESCRIPTION

ROCKER ARMS

2007 Dodge Nitro R/T

2007 ENGINE 4.0L - Service Information - Nitro

Fig. 153: Rocker Arm Assembly
Courtesy of CHRYSLER LLC

Rocker arms are made of light weight permanent mold aluminum alloy with a roller (3) type follower operating

1 - RETAINER
2 - SWIVEL PAD
3 - ROLLER

2007 Dodge Nitro R/T

2007 ENGINE 4.0L - Service Information - Nitro

against the camshaft. See Fig. 153. The valve actuating end of the rocker arms are machined to retain hydraulic
lash adjusters, eliminating the need for manual valve lash adjustment.

ROCKER ARM SHAFTS

Fig. 154: Rocker Arms & Shafts
Courtesy of CHRYSLER LLC

The rocker arm shafts are tubular steel and are supported by several forged aluminum alloy pedestals, which are
fastened to the cylinder head. Four shafts are used, one for each intake and exhaust rocker arm bank on each
cylinder head. The shafts are hollow to provide a duct for lubricating oil flow from the cylinder head to the
valve mechanisms. One hollow dowel per pedestal is used to locate the pedestal to the cylinder head, orient the
exhaust rocker shaft, and serve as a cam bearing oil feed passage. See Fig. 154.

OPERATION

ROCKER ARMS

The rocker arm is the pivot point between the camshaft lobe and the valve.

DIAGNOSIS AND TESTING

LASH ADJUSTER (TAPPET) NOISE DIAGNOSIS

Proper noise diagnosis is essential in locating the source of a NVH complaint. Locating a lash adjuster (tappet)
type noise can sometimes be difficult. As a result, an initial misdiagnosis may occur.

Refer to the following chart indicating possible lash adjuster (tappet) noise sources and possible sources that
could lead to a misdiagnosis.

2007 Dodge Nitro R/T

2007 ENGINE 4.0L - Service Information - Nitro

Refer to Lash Adjuster (Tappet) Noise Chart for Possible Causes and Correction of a lash adjuster (tappet) type
noise.

LASH ADJUSTER (TAPPET) NOISE CHART

POSSIBLE NOISE SOURCES

POSSIBLE NOISE MISDIAGNOSIS SOURCES

Spongy/soft/aerated lash adjusters.

Exhaust leak.

Missing lash adjuster swivel contact pads.

Exhaust rocker arm-to-cylinder head cover contact.

Intake rocker-to-camshaft bearing journal contact.

Piston pin bore fit.

Rocker arm bind-up.

Timing drive hydraulic tensioner tick.

Intake rocker arm-to-spark plug tube contact.

Accessory drive belt deterioration.

Excessive cam end play.

Piston-to-bore clearance knock.

Broken valve spring.

Crankshaft bearing noise.

Broken/loose camshaft sprocket bolt.

Incomplete cam lobe machining.

Cracked lash adjuster cartridge body.

POSSIBLE CAUSES

CORRECTION

1. Engine oil level-too high or too low. This may
cause aerated oil to enter the adjusters and cause
them to be spongy.

1. Check and correct engine oil level.

2. Insufficient running time after rebuilding cylinder
head.

2. Low speed running of up to 1 hour may be
required to fully evacuate trapped air from the valve
train system. During this time, turn engine off and
let set for a few minutes before restarting. Repeat
this several times after engine has reached normal
operating temperature.

3. Air trapped in lash adjuster (after 1 hour run
time).

3. See below:
(a) Check lash adjusters for sponginess while
installed in cylinder head. Depress part of rocker
arm over adjuster. Normal adjusters should feel very
firm. Very spongy adjusters can be bottomed out
easily.
(b) Before proceeding, perform Lash Adjuster
Bleeding procedure.
(c) If lash adjuster(s) are still spongy, replace with
new adjuster/rocker arm assembly*.

4. Low oil pressure

4. See below:
(a) Check and correct engine oil level.
(b) Check engine oil pressure.
(c) Check for excessive bearing clearance and
correct.
(d) Check for worn oil pump.

5. Oil passage to cylinder head(s) plugged with
debris.

5. Check cylinder head oil passages and cylinder
head gasket restrictor for blockage. Clean or replace

2007 Dodge Nitro R/T

2007 ENGINE 4.0L - Service Information - Nitro