Engine - Knocking, Rattling/Tapping Noise

BULLETIN NUMBER:
SB99-01-S001

ISSUE DATE:
JANUARY 1999

GROUP:
ENGINE

1996-97 HOMBRE (TH) 2.2L ENGINE: KNOCK, RATTLE, AND TAP NOISE

AFFECTED VEHICLES

1996-97 Hombre (TH) models equipped with 2.2L engine.

SERVICE INFORMATION

Condition:
On some affected vehicles, the engine may emit a knocking, rattling, tapping, or ticking noise before it has reached operating temperature. The noise may also occur at operating temperature under light load or deceleration conditions. This noise does not result in any damage but may be objectionable to some vehicle owners.

This noise should not be confused with other sources of noise such as accessory drive ticks, exhaust system rattles, clutch or flywheel noise, etc.

Possible Cause:
Under certain conditions, the piston may be excessively rocking in the cylinder bore.

Diagnosis:
If possible, have the customer leave the vehicle overnight to allow the engine to stabilize at ambient temperature. Start the vehicle and as soon as possible, operate the engine between 2,000 and 2,200 RPM. if necessary, on automatic transmission equipped models, shift the vehicle manually into 1st or 2nd gear to maintain the RPM range when driving.

IMPORTANT
In manual 1st or 2nd, the vehicle may not be able to maintain normal traffic speed within the range between 2,000 and 2,200 RPM. Be aware that other drivers may not be prepared for a vehicle traveling at a much slower speed. If possible, attempt to go to a rural area or to an area that has light traffic.

NOTE
The noise may be louder if the ambient temperature is cooler and will be much less noticeable with the engine at operating temperature.

Correction:
To correct this condition, replace all of the piston and rod assemblies using part numbers listed in the Parts Information section of this bulletin. Follow the procedures outlined in this bulletin and the appropriate Workshop Manual for the proper service procedure.

SERVICE PROCEDURE

1. Remove the engine accessory bracket to expose the front of the engine block and cylinder head mating area.

2. Inspect the engine to see if it has a bright orange or red letter "A" marking. This marking is located on the front of the engine block behind the accessory bracket, directly above the timing chain housing cover and below the engine block-to-cylinder head mating area. If so, the pistons must be replaced using the appropriate part numbers from the table in the Parts Information section of this bulletin.

3. Disassemble the engine as needed to remove the pistons using the service procedures outlined in Engine Mechanical section of the appropriate Workshop Manual. If this engine has the "A" marking, disassemble the pistons from the rods and discard the pistons.

4. Using a ball-type or self-centering honing tool, deglaze the cylinder bore lightly, only to remove any deposits that may have formed.

5. For engines with "A" marking, assemble the pistons to the connecting rods using J 24086-C.

IMPORTANT
Prior to assembly, it is necessary to properly orient the pis tons on the connecting rod and to orient the piston rod assembly properly in the engine to prevent noise. Inspect the lower end of the connecting rod on one side of the connecting rod, and located a "bump" that points toward the small end of the connecting rod. This "bump" is located at the top of the thrust face of the connecting rod where the beam of the connecting rod forms into the large end. This "bump" should face away from the arrow on the piston crown.

NOTE
It is necessary to use tool J 24086-C or a fixture that does not put pressure against the piston. All press loads must be supported by the connecting rod. Any load on the piston or piston skirt will distort the piston.

6. Inspect the piston rod bearings for wear using service procedures outlined in the Workshop Manual. If necessary, replace with the correct size as indicated by the measurements taken. Three sizes are available from AIPDN.





7. Scrub the cylinder bore and replacement pistons with soapy water to remove any foreign material. Thoroughly dry the parts, install new piston rings (Figure 1), and coat the cylinder bore, piston skirt, and piston rings, with engine oil.

8. Install all four (4) pistons or piston and rod assemblies using the service procedures outlined in the Workshop Manual.

IMPORTANT
All four pistons must be replaced.





PARTS INFORMATION

WARRANTY CLAIM INFORMATION





Use the published labor operation as shown.

Labor Time includes administrative time allowance.