Cummins Killer Dowel Pin: Which Engines, Signs and the Fix

The killer dowel pin, or KDP, is a small locating pin pressed into the front of the 5.9 Cummins block behind the timing gear housing. On some engines it can work loose over time, fall into the timing gears and cause serious damage, from a broken gear housing to a ruined timing gear set. It is most associated with the 12-valve 5.9 Cummins used in 1989 to 1998 Dodge trucks, and many owners of early 24-valve engines check theirs as well. The fix is a tab kit that bolts over the pin so it cannot back out.

Why it is called the killer dowel pin

The pin locates the gear housing during assembly and does little after that. Heat cycling can loosen it in its bore. When it walks out, it can drop into the gear train, and the damage happens without much warning, which is how it earned its name.

Which engines are affected

The issue is tied mainly to 12-valve engines. Some owners of early 24-valve engines inspect the pin too, since the parts are similar. Later common-rail engines are not usually discussed in connection with it. If you are unsure, inspecting the pin while the timing cover is off for other work is cheap insurance.

Signs the pin is loose

• Often none before failure, which is why many owners fix it preventively.
• A new ticking or rattling from the timing cover area.
• Coolant or oil leaks near the timing cover after a gear housing crack.

How the fix is done

1. Remove the fan shroud, fan and belt, and often the radiator for room.
2. Remove the crank pulley and damper, then the timing cover.
3. Check the pin’s position; if it has moved, tap it back into its bore.
4. Bolt the tab from the kit over the pin using the gear housing bolt it is designed for.
5. Refit the timing cover with a new gasket and front crank seal, then reassemble.

Follow the kit maker’s instructions and torque values. While the cover is off, it is a good time to inspect the timing gears and front seal.

Other 5.9 Cummins weak points

The KDP is one of several known issues; see 5.9 Cummins problems, 12-valve vs 24-valve vs common rail and Cummins generations. For specs, see 5.9 Cummins specs.

If the damage is done

A pin that has gone through the gears can crack the gear housing or block. If the damage is extensive, a replacement engine may be the practical route; see the engines on 5.9 Cummins engines and Cummins engines, and budget with engine replacement cost.

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