The 6.7L Cummins uses an intake grid heater to warm incoming air for cold starts. It is a good system, but it hides a serious flaw that every owner should know about: the bolt that holds the grid heater together can fail and drop into the engine. When it does, the damage can be catastrophic.
What the grid heater does
Diesel engines do not use spark plugs, and Cummins engines do not use glow plugs either. Instead, the 6.7L relies on an intake grid heater, an electric heating element in the intake that warms the incoming air to aid cold starting and smooth out cold running. It is an effective, simple system that most owners never think about, until the mounting hardware becomes a problem.
Why the bolt is dangerous
The grid heater is fed power through a stud and secured with a small bolt, often referred to as the #10 bolt. Over years of heat cycling and electrical current, that bolt can loosen, weaken, or break. Because it sits right at the intake, a failed bolt can fall directly into the engine's intake path and get pulled into a cylinder.
- A dropped bolt can bounce between the piston and valves, causing severe internal damage.
- Bent valves, damaged pistons, and scored cylinders are all possible outcomes.
- In the worst cases, the engine is destroyed and requires a rebuild or replacement.
The frightening part is that it can happen with little warning on an otherwise healthy engine.
Which trucks are at risk
The concern applies broadly across 6.7L Cummins engines that use the grid heater with this style of mounting hardware. Because the failure is tied to age, heat cycles, and electrical wear, higher-mileage and older trucks are generally considered more at risk, but owners of all 6.7L trucks should be aware of it.
How owners eliminate the danger
There are a few common approaches:
- Grid heater delete or bung kit. Some owners remove the grid heater entirely and install a spacer or block-off. This removes the hardware that can fail. Keep in mind that removing the grid heater affects cold-start behavior, which matters in cold climates.
- Upgraded or secured hardware. Others address the bolt directly with better hardware or by ensuring it is properly secured, preserving cold-start function while reducing the failure risk.
- Inspection. At minimum, have the grid heater and its bolt inspected. Catching a loose or corroded bolt early is far cheaper than the alternative.
Which route is right depends on your climate and how you use the truck. If you rely on the grid heater for cold starts, securing or upgrading the hardware may make more sense than deleting it.
Frequently asked questions
Does the 6.7L Cummins have glow plugs?
No. Cummins engines do not use glow plugs. The 6.7L uses an intake grid heater to warm incoming air for cold starts. That grid heater is where the bolt-failure concern comes from.
How do I know if my grid heater bolt is a problem?
There is often no obvious symptom before failure, which is why inspection is important. Have the grid heater and its mounting bolt checked for corrosion, looseness, or damage, especially on higher-mileage trucks.
Should I delete my grid heater?
It depends on your climate. Deleting removes the failure risk but hurts cold-start performance, which matters in cold regions. Many owners in warm climates delete it, while those in cold areas prefer to secure or upgrade the hardware. Email sales@coredieselparts.com to talk through the best option for your truck.
Need parts or a second opinion on a diagnosis? The team at Core Diesel Parts can help you match the right components to your truck. Email sales@coredieselparts.com with your year, engine, and symptoms and we will point you in the right direction.
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