Unlike Power Stroke and Duramax diesels, the Cummins uses an intake grid heater to warm incoming air for cold starts, not glow plugs. The grid heater sits in the intake between the intake horn and the manifold. On the 6.7L Cummins in particular, the bolt that secures the grid heater terminal has a reputation for loosening or failing and dropping into the engine, so many owners address the grid heater proactively. Here is how to replace it safely.
Why owners service the grid heater
- Weak or no cold-start assist, causing hard cold starts and white smoke
- On the 6.7L, concern over the grid heater bolt backing out and being ingested
- Corrosion or electrical faults at the terminal stud
- An electrical code related to the intake air heater circuit
Step-by-step replacement
- Disconnect the batteries. The grid heater carries very high current, so this is not optional.
- Remove the intake horn or air inlet piping to expose the top of the intake and the grid heater terminal stud.
- Note and label the heavy power cable and any sensor connectors, then disconnect them.
- Remove the intake horn bolts and lift the horn to access the grid heater element between the horn and the manifold.
- Remove the old grid heater and gaskets. Inspect the terminal hardware carefully; on the 6.7L this is the notorious bolt.
- Clean the sealing surfaces and install the new grid heater with fresh gaskets, following the correct orientation.
- Reinstall the intake horn, torque all fasteners, especially the terminal stud hardware, to spec, and reconnect the power cable securely.
- Reconnect the batteries and verify the grid heater cycles on a cold start.
The 6.7L grid heater bolt
On the 6.7L Cummins, the small bolt securing the grid heater's electrical terminal is a known weak point. If it loosens and drops, it can be pulled into the engine with serious consequences. When you have the intake apart, inspect this hardware, use the correct updated fastener, and torque it precisely. Some owners install a redesigned grid heater or a delete of the internal bolt hazard using a purpose-built kit, but any change to the intake air heater should keep cold-start function intact.
Getting a reliable result
Because the grid heater draws enormous current, electrical integrity is everything:
- Always disconnect the batteries before touching the terminal stud.
- Clean and tighten the power cable connection so it does not arc or overheat.
- Torque the terminal hardware exactly to spec, not by feel.
- Verify the grid heater actually cycles by watching for the wait-to-start behavior and the brief voltage draw on a cold start.
A healthy grid heater means clean, quick cold starts with minimal white smoke. If cold starting is still poor afterward, confirm battery health and the heater relay next.
Frequently asked questions
Does a Cummins have glow plugs?
No. Cummins diesels use an intake grid heater to warm incoming air. Glow plugs are found on Power Stroke and Duramax engines.
Why is the 6.7L grid heater bolt a concern?
The terminal bolt can loosen and drop into the intake, where it may be ingested by the engine. Inspecting and correctly torquing that hardware is a key part of the job.
How do I know my grid heater is working?
On a cold start it should cycle, drawing high current briefly and reducing white smoke. A weak cold start with heavy smoke suggests a failed heater or relay. Need parts? Email sales@coredieselparts.com.
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