Cummins N14 STC, Celect, Celect Plus – Service Manual 002-032   Cylinder Head Capscrews

Use a petroleum-based solvent to clean the capscrews.

Clean the capscrews thoroughly with a wire brush, a wire wheel (soft), or use a non-abrasive bead blast to remove the deposits from the body and threads.

Inspect the cylinder head capscrews for damaged threads, corroded surfaces, or a reduced diameter (due to capscrew stretching).

NOTE: Do not reuse a capscrew that has damaged threads or a reduced diameter from having been stretched.

Do not reuse cylinder head capscrews with corrosion or pitting that exceeds 1 sq cm [0.155 sq in] in area.

Example:

Acceptable: [3/8 x 3/8 in]

Unacceptable: [1/2 x 1/2 in]

Do not reuse cylinder head capscrews with corrosion or pitting that exceeds 0.12 mm [0.005 in] in depth.

Do not reuse cylinder head capscrews if corrosion or pitting is located within 3.2 mm [0.125 in] of the fillet or threads.

Using the flange head capscrews with the torque plus angle method of installation places the capscrew beyond the yield point, and permanently stretches the capscrew at each use. These capscrews can be reused throughout the life of the engine unless the capscrew exceeds the specified free length. The capscrew free length must be checked to avoid bottoming out in the cylinder block during installation.

Use service tool, Part Number 3823546, to check the capscrew free length.

The capscrews can be checked using a set of calipers if service tool, Part Number 3823546, is not available. The maximum allowable free length (dimension ‘X’), measured from the bottom of the flange to the end of the capscrews, is 185.6 mm [7.130 in].

To check the capscrew free length, place the head of the capscrew in the appropriate slot with the flange against the base of the slot.

NOTE: Capscrew length must be checked without the hardened washer.

If the end of the capscrew touches the foot of the gauge, the capscrew is too long and must be discarded.

The capscrew can be used again if there is clearance between the end of the capscrew and the bottom base of the tool.

Immediately after cleaning and inspecting, apply a film of clean engine lubricating oil to capscrews that are to be used again.