2005/04/11 Caterpillar

Engine: Commercial

3500 and 3500B Family All

Engine News SEBD9349, April 2005, "Tightness of Bolted Joints with the Torque Turn Procedure". Disregard this article. The following information is correct.

The 3500 Engines have several bolted joints that use a torque turn procedure at assembly. These bolted joints include main bearing caps, cylinder heads, and crankshaft counterweights.

In order to tighten the bolts, a specific preliminary torque is applied. This is followed by a torque-turn angle that is measured in degrees. The resultant torque will vary greatly due to the following factors: properties of the material, metallurgical properties and environmental conditions. Due to these variables, tightening bolts to a specific torque would yield significantly different clamping force. In certain critical joints, a minimal variation of clamping force is important.

To ensure the proper bolt stretch and the proper clamping force, the torque turn procedure is used. As a result of this procedure, it is not possible to verify the tightness of this type of joint after assembly.

Refer to the following articles:

• Engine News, SEBD9264, "Recommended Lubrication and Torque Procedure for Main Bearing Cap Bolts"

• Engine News, SEBD9264, "Recommended Lubrication and Torque Procedure for Connecting Rod Bolts"

• Engine News, SEBD9264, "Recommended Lubrication and Torque Procedure for Crankshaft Counterweight Bolts"

• Engine News, SEBD9335, "Procedure for Cylinder Head Bolt Tightening"

• Guideline for Reusable Parts and Salvage Operations, SEBF8301, "Inspection and Reuse of Critical Fasteners Used in All Engines"