2024–2025 GM LK0 Coolant Smell? Inspect the Cylinder Head Before Calling It a Hose

Coolant Smell From The Top?

A coolant smell from the top of a 2.5L LK0 engine should start a search, not a hose order. On the GM vehicles covered by bulletin 24-NA-184, the trail can begin at porous spots in the cylinder head. The useful sequence is to cool the engine, preserve the highest fresh wet point, rule out accessible external connections, and inspect the spark-plug bore and head casting only after that evidence points inward.

When a normal sight line ends at a deep bore, a small articulating camera can preserve what the technician sees before cleaning or disassembly changes it. The AUTOOL SVB208 automotive borescope is one way to record that hidden surface. It cannot identify a liquid by sight, see through the casting, prove porosity from one stain, remove spark plugs safely, or authorize cylinder-head replacement.

Think in four images: the dry landmark, the first wet point, the path into the bore, and the same location after a controlled repeat. That small photo grid is more useful than a dozen disconnected close-ups.

Cool the engine before preserving the scene

If the temperature warning appears, steam is present, or coolant is escaping rapidly, shut the engine down and arrange recovery. Do not remove a hot pressure cap. A hot system can release scalding liquid, and topping up before documenting the level can erase the rate and location of loss.

After a complete cold soak, photograph the reservoir level and the upper engine before cleaning anything. Record mileage, outside temperature, trip length, odor timing, previous top-ups, heater performance, and whether the wetness appeared before or after recent service. Place clean absorbent material beneath the vehicle if safe, but keep pets and children away from coolant.

Odor alone is not source proof. Residue from a prior spill can smell again when warm, and airflow can carry vapor away from the actual leak.

Open the LK0 bulletin fence

GM 24-NA-184 names the 2025 Buick Enclave and 2024–2025 Chevrolet Traverse and GMC Acadia with the 2.5L LK0 in North America. Confirm the VIN, engine RPO, build data, previous repairs, and the latest GM service information. A similar-looking engine or the same symptom outside that fence does not inherit the bulletin’s cylinder-head conclusion.

The document is technical service guidance, not a recall notice and not automatic warranty approval. Check the VIN separately for open programs. Even a covered vehicle may have an ordinary hose, cap, pump, housing, radiator, reservoir, heater, turbo-cooling, or service-spill issue.

Trace the highest fresh wet point

Coolant travels down castings, collects in pockets, and is blown rearward by airflow. Start at the highest accessible dry surface and move downward in short sections. A forming bead or a wet edge that returns after drying matters more than a crusty deposit at the bottom of the engine.

Use consistent lighting. Photograph a wide landmark view, a mid-range route view, and a close view of the suspected source. Note whether the liquid is newly forming or merely reflective residue. If approved dye is already present, follow current GM instructions for interpreting it; color under a lamp still does not tell you whether the source is above the point photographed.

Clear the external connections first

Inspect accessible hose joints, quick-connects, clamps, coolant outlets, reservoir seams, vent paths, and evidence of earlier filling. Look for a clean track through surrounding dust, a first wet edge, or residue that begins above the cylinder head. Do not tighten a connection speculatively; overtightening can damage plastic fittings or move the evidence.

A cold pressure test may help reproduce a leak, but pressure, cap, adapter, and time must come from current service information. More pressure is not more proof. Confirm the tester and adapter hold before interpreting a falling needle, and never substitute shop air.

Observation	Next justified move	What it does not prove
Fresh bead at an external connector	Document and repair that source	The cylinder head also leaks
Pressure drops and the upper exterior stays dry	Inspect the named hidden areas	Porosity by itself
Old residue does not return	Clean, heat-cycle, and watch	An active leak
Coolant appears in a plug bore	Preserve the path and follow GM diagnosis	Casting source without repeat evidence

Inspect the plug bore only after access is earned

Spark-plug removal belongs with a cooled engine, controlled ignition/fuel state, clean wells, correct tools, and the current torque procedure. Debris dropped into a cylinder or thread damage can create a second repair. Index every plug and coil by cylinder before moving them.

GM directs technicians to inspect the spark-plug bore and cylinder-head area for coolant seepage. Enter with the camera centered, avoid scraping seals or electrodes, and establish orientation with a recognizable feature. Record a slow pass rather than spinning the probe. A shiny surface may be fuel, oil, coolant, cleaner, or optical glare; context and a repeatable wet path are essential.

Build a four-view seepage record

Organize the evidence so another technician can reconstruct it:

1. A wide view showing which bank, cylinder, and side of the engine is involved.
2. A dry approach view showing the highest clean landmark.
3. A close bore/head view showing where liquid first appears.
4. A repeat view after the approved pressure or heat condition, at the same angle.

Add the cold level, test pressure and duration, cap/adapter used, cylinder identity, and whether other external areas stayed dry. This is not decoration; it separates a migrating drip from seepage that begins at the casting.

Leave porosity unproved when the casting stays dry

If the scoped areas remain dry and the pressure record is stable, stop forcing the bulletin to fit. Expand the search to the water pump, radiator, reservoir/cap, heater circuits, turbocharger coolant routes, underbody traces, interior heater-core evidence, and internal loss only as current diagnostics direct.

If the bore is wet but the path begins at an external fitting above it, repair the upstream source first. If coolant loss continues with no external evidence, a professional may need combustion-gas, oil, plug, compression, or cylinder evidence. None of those tests should be inferred from a single odor.

Verify cold level after controlled heat cycles

After the confirmed repair, clean old residue by the approved method, restore every connector and fastener, fill and bleed with the specified coolant, and repeat the same cold pressure check. Heat-cycle the system far enough to open the relevant paths while monitoring temperature and heater operation.

Let the vehicle cool fully on level ground. Compare the reservoir with the first photograph, then recheck the same four image locations. A successful result is a stable cold level, no returning odor or first-wet point, a dry documented route, normal temperature, and no new code—not simply a clean floor after one short idle.

Official references

• GM bulletin 24-NA-184: LK0 coolant leak or smell from the top of the engine
• GM VIN recall and program lookup