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