Dodge Nitro. Manual — part 40

Fig. 118: Measuring Cylinder Diameter With Bore Gauge - Typical
Courtesy of CHRYSLER LLC

1. To correctly select the proper size piston, a cylinder bore gauge (2), capable of reading in 0.003 mm

(.0001 in.) INCREMENTS is required. If a bore gauge is not available, do not use an inside micrometer.
See Fig. 118.

1 - FRONT
2 - BORE GAUGE
3 - CYLINDER BORE
4 - 38 MM
(1.5 in)

2007 Dodge Nitro R/T

2007 ENGINE 3.7L - Service Information - Nitro

2. Measure the inside diameter of the cylinder bore (3) at a point 38.0 mm (1.5 inches) below top of bore.

Start perpendicular (across or at 90 degrees) to the axis of the crankshaft at point A and then take an
additional bore reading 90 degrees to that at point B.

Fig. 119: Moly Coated Piston
Courtesy of CHRYSLER LLC

3. The coated pistons (1,2) will be serviced with the piston pin and connecting rod pre-assembled. See Fig.

119.

4. The coating material is applied to the piston after the final piston machining process. Measuring the

outside diameter of a coated piston (1,2) will not provide accurate results. Therefore measuring the inside
diameter of the cylinder bore with a dial Bore Gauge is MANDATORY . To correctly select the proper
size piston, a cylinder bore gauge capable of reading in 0.003 mm (.0001 in.) increments is required.

5. Piston installation into the cylinder bore requires slightly more pressure than that required for non-coated

pistons. The bonded coating on the piston will give the appearance of a line-to-line fit with the cylinder
bore.

1 - MOLY COATED
2 - MOLY COATED

2007 Dodge Nitro R/T

2007 ENGINE 3.7L - Service Information - Nitro

REMOVAL

REMOVAL PISTON AND CONNECTING ROD

1. Disconnect negative cable from battery.

2. Remove the following components:

Oil pan and gasket/windage tray. See REMOVAL.

Cylinder head covers. See REMOVAL)

Timing chain cover. See REMOVAL).

Cylinder head(s). See REMOVAL.

3. If necessary, remove top ridge of cylinder bores with a reliable ridge reamer before removing pistons

from cylinder block. Be sure to keep tops of pistons covered during this operation. Pistons and
connecting rods must be removed from top of cylinder block. When removing piston and connecting rod
assemblies from the engine, rotate crankshaft so the each connecting rod is centered in cylinder bore.

4. Mark connecting rod and bearing cap positions using a permanent ink marker or scribe tool.

5. Remove connecting rod cap. Install the Connecting Rod Guides 8507 into the connecting rod being

removed. Remove piston from cylinder bore. Repeat this procedure for each piston being removed.

6. Immediately after piston and connecting rod removal, install bearing cap on the mating connecting rod to

prevent damage to the fractured cap and rod surfaces.

CLEANING

PISTON AND CONNECTING ROD

CAUTION: DO NOT use a number stamp or a punch to mark connecting rods or

caps, as damage to connecting rods could occur

NOTE:

Connecting rods and bearing caps are not interchangeable and should be
marked before removing to ensure correct reassembly.

CAUTION: Care must be taken not to damage the fractured rod and cap joint

face surfaces, as engine damage may occur.

CAUTION: Care must be taken not to nick crankshaft journals, as engine

damage may occur

CAUTION: DO NOT use a wire wheel or other abrasive cleaning devise to clean the

pistons or connecting rods. The pistons have a Moly coating, this coating
must not be damaged.

2007 Dodge Nitro R/T

2007 ENGINE 3.7L - Service Information - Nitro

1. Using a suitable cleaning solvent clean the pistons in warm water and towel dry.

2. Use a wood or plastic scraper to clean the ring land grooves.

INSPECTION

PISTON AND CONNECTING ROD

Check the connecting rod journal for excessive wear, taper and scoring.

Check the connecting rod for signs of twist or bending.

Check the piston for taper and elliptical shape before it is fitted into the cylinder bore.

Check the piston for scoring, or scraping marks in the piston skirts. Check the ring lands for cracks and/or
deterioration.

INSTALLATION

PISTON AND CONNECTING ROD

CAUTION: DO NOT remove the piston pin from the piston and connecting rod

assembly.

2007 Dodge Nitro R/T

2007 ENGINE 3.7L - Service Information - Nitro