I have had my GMC sierra 1500 for almost 3 years. I have a little under 59,000 miles on the truck. A few thousand miles ago a tech at the gm dealer let me know that they had to add some coolant and it was something I should keep an eye on. I brought the vehicle back to have them look into it. They let me know that the radiator has a small leak. It is not big enough to have fluid hit the…
2018 GMC Sierra engine problems
moderate 39 complaints filed with NHTSA · avg repair $3,100 · see engine across all vehicles →
Failure mileage
Complaints
39
Recalls
0
Avg fix
$3,100
When does it fail?
Of the 39 engine complaints filed for the 2018 GMC Sierra, here's the actual mileage breakdown — failures cluster heaviest at 25,000-50,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
What stands out
Owners have filed 39 engine complaints with NHTSA against this vehicle, but no formal recall covers the issue — the federal record reflects what manufacturers have admitted, not everything owners are reporting.
No new NHTSA engine complaint has been filed on this vehicle in over 5 years — the issue may be aging out of the active population.
The failure pattern owners describe
The 2018 GMC Sierra 1500 accumulates complaints centered on four recurring engine and cooling system failures. AFM lifter collapse dominates the cluster—owners describe sudden violent shuddering, power loss, and engine noise between 17,000 and 169,000 miles, with diagnostic scans showing misfire codes (P0301, P0307, P0308). Internal inspection repeatedly finds broken lifters, bent pushrods, scored camshafts, and metal debris; most require full engine replacement ($12,000–$14,200). Many failures occur just outside or beyond the 5-year/60,000-mile powertrain window, leaving owners unprotected. Radiator coolant leaks occur routinely in the 40,000–60,000-mile range with no warning lights; one dealership confirmed stocking replacements as standard practice, yet GM denies warranty coverage. Fuel injector failures trigger repeated misfire codes and sudden power loss during highway driving; one case at under 6,000 miles and another showing severe gasoline contamination in oil analysis. Engine structural failures—connecting rod failure, spun main bearings, and spontaneous shutdown at 78 mph—occur without preceding warning. Across all failures, GM either denies warranty, provides no assistance, or opens a case without resolution. Multiple owners report researching online and finding many similar failures, and dealers openly acknowledge these as known recurring issues for the model.
Same GMC Sierra engine reports on nearby years: 2015 · 2017 · 2019 · 2020 · 2021
Failure modes owners describe
AFM Lifter Failure
The Active Fuel Management (AFM) lifter mechanism fails catastrophically, often breaking apart or collapsing internally. This causes the pushrod to bend, camshaft to score or become damaged, and metal debris to circulate in the engine. Owners report the failure can occur suddenly while driving, creating a safety hazard.
When: Between 17,000 and 169,000 miles; most commonly reported in the 40,000–90,000-mile range, with some occurring just outside or beyond the 60,000-mile powertrain warranty window.
Symptoms owners cite: Sudden dramatic shuddering and loss of power while driving; Check engine light illumination (often P0301, P0307, P0308 misfire codes); Abnormal ticking, knocking, banging, or popping sound from engine; Reduced power or hesitation upon acceleration; Smoke from exhaust or engine compartment; Engine vibration and running rough; Excessive oil on spark plugs; Low cylinder compression (75 PSI vs. 200+ PSI normal); Metal shavings or debris found inside engine
Codes mentioned: P0301, P0307, P0308
Repairs/costs cited: Full engine replacement typically required due to extent of internal damage; ranges from $12,000–$14,200+ per owner reports. Some owners report $8,400 for lifter, camshaft, and pushrod replacement, but complete engine replacement is the common outcome.
Recalls/TSBs owners mention: No recall identified for most VINs; GM may open case number for review but provides no financial assistance. Warranty denial common because failure often occurs just outside the 5-year/60,000-mile powertrain window.
Fuel Injector Failure
Fuel injectors fail internally, causing repeated misfire conditions and fuel delivery issues. In one case, an injector O-ring split, leaking fuel onto the manifold. This leads to loss of power, hesitation, and poor acceleration.
When: One complaint at under 6,000 miles; another at 88,400 miles with oil analysis showing severe gasoline contamination.
Symptoms owners cite: Repeated misfire codes (P0300, P0307); Sudden loss of power and hesitation while driving; Engine struggles to accelerate, especially at highway speeds or during merging; Smell of gasoline; Poor fuel economy; Lack of acceleration response; Gasoline contamination in engine oil (detected via oil analysis)
Repairs/costs cited: Injector replacement performed at dealership; one owner reports replacement of both fuel injectors and high-speed fuel pump. Three-month out-of-service period noted in one complaint.
Recalls/TSBs owners mention: Service Bulletin 18-NA-137 addresses fuel injection seal issue; covered under warranty if within period. Beyond warranty, repairs are owner responsibility.
Radiator Coolant Leak
Radiators develop leaks, typically along outer edges or at seal points, causing coolant loss without obvious external cause. Multiple owners report this is a known recurring issue; one dealer reports stocking replacement radiators as a matter of routine for this model.
When: Reported between 42,000 and 60,000 miles, well before typical component life expectancy.
Symptoms owners cite: Coolant smell emitting from vehicle; Abnormal rate of coolant loss requiring frequent replacement; Temperature gauge rising during driving, especially under towing load; Coolant dripping from front of vehicle; Visible crack in radiator upon inspection; No warning lights alerting to malfunction
Repairs/costs cited: Radiator replacement; one owner paid $876 and received only $250 from GM warranty contribution.
Recalls/TSBs owners mention: GM denies warranty coverage for most radiator failures in the 2018 model year, citing it as out of warranty. Prior TSBs exist for 2014–2017 models but do not cover 2018 model year, despite identical design.
Engine Knock, Ticking, and Structural Failure
Owners report abnormal internal engine noise (ticking, knocking, popping), metal shavings in the oil, and catastrophic structural failures including bent connecting rods and spun main bearings. One vehicle experienced a complete engine shutdown at highway speed with oil pouring from a hole in the block.
When: Failures range from 17,000 miles (ticking at startup) to 150,000 miles; one catastrophic failure at 58,000 miles.
Symptoms owners cite: Abnormal ticking, knocking, or popping sound at startup or while driving; Metal shavings discovered inside engine; Complete engine failure with loss of power at highway speed (78 mph reported); Oil pouring from engine block; Vehicle shuts down with no warning; No warning lights preceding failure
Repairs/costs cited: Engine replacement required; one owner reported $14,221.96 for full engine replacement at 65,449 miles.
Recalls/TSBs owners mention: Manufacturer notified but case remains unresolved; some referred to NHTSA Hotline. No recall identified for affected VINs.
Reduced Power / Stall Conditions
Vehicle suddenly loses power or stalls without warning during driving, displaying 'Reduced Power' messages or no warning at all. Symptoms include jerking, hesitation on acceleration, and inability to restart reliably. One complaint involved multiple component failures (starter, battery, fuel pump, oil pump, oil pump sensors, fuel injectors) that recurred after repair.
When: Between 72,000 and 169,000 miles.
Symptoms owners cite: Sudden loss of power without warning light; Vehicle stalls while driving; Hesitation before accelerating from stoplight; 'Reduced Power' message displayed; RPMs increase abnormally; Jerking motion of vehicle; Hard time restarting after stall; Smoke from exhaust; Vehicle unable to maintain speed
Codes mentioned: P2635
Repairs/costs cited: One case involved replacement of starter, battery, fuel pump, oil pump, oil pump sensors, and fuel injectors; failure recurred despite repairs. Vehicle parked out of service at owner's report.
Recalls/TSBs owners mention: Manufacturer notified but provided no assistance; vehicle remains unrepaired in at least one case.
Exhaust Manifold Bolt Fracture
Exhaust manifold mounting bolts fracture, causing potential for exhaust leakage and structural instability.
When: 64,000 miles.
Symptoms owners cite: Abnormal ticking sound from engine compartment
Repairs/costs cited: Exhaust manifold bolts require replacement.
Engine Mount Failure (Driver's Side)
Driver's-side engine mount cracks or wears prematurely, risking engine separation from vehicle frame.
When: At or before 5 years of age (2018 model).
Symptoms owners cite: Dealership diagnosis of cracked or worn engine mount; Risk of engine falling out if not replaced
Repairs/costs cited: Engine mount replacement required.
Fuel Vaporization and Hard Start (Hot Climate)
In hot ambient temperatures (over 100°F), fuel vaporizes in the fuel lines after prolonged idle or low-speed operation, preventing reliable engine restart.
When: Chronic issue in high-ambient-temperature environments; long idle periods and low-speed driving under 25 mph.
Symptoms owners cite: Engine stalls after long periods of running or idle; Hard time restarting; Check code P2635 and random secondary codes; Gas pedal depression sometimes helps restart
Codes mentioned: P2635
Repairs/costs cited: Dealership indicated fuel vaporization in lines but noted TSB PIP5507B does not cover 2018 model year despite unchanged design.
Recalls/TSBs owners mention: TSB PIP5507B exists but does not include 2018 model year coverage.
Radiator Condenser Leak (AC System)
AC condenser on radiator leaks at the same location as noted in prior-year TSBs, causing loss of coolant to the cooling system and inability to maintain AC cooling.
When: At 2 years 3 months of ownership; vehicle is out of warranty by mileage.
Symptoms owners cite: AC blowing warm air; Coolant loss (separate from AC refrigerant issue)
Repairs/costs cited: Condenser replacement required; warranty denied due to mileage.
Recalls/TSBs owners mention: Prior TSBs exist for 2014–2017 model years; 2018 model not covered despite recurring issue.
Excessive Oil Consumption and Metal Debris (6.2L AFM)
6.2L engine with AFM system exhibits extreme oil consumption and elevated metal particulate in oil analysis, indicating internal wear or damage.
When: At 120,789 miles.
Symptoms owners cite: Extreme oil consumption; Heavy metal in oil (detected via analysis); Loud ticking from engine
Repairs/costs cited: Engine inspection available; repair details not specified.
Synthesized from 39 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 3 most recent
This vehicle has 88400 miles, it out of warranty, which I know this, I use amsoil asm sig series syn SAE 0w-20 , 5.3l gas. Two years ago, I changed oil at richard Buick GMC in dayton, oh and sent a sample of the oil to oil analyzers for an analysis, they set it back, it showed there was a level 4 severe gasoline in the oil. They changed the high speep fule pump, both in jectors, and it thought it…
Tl* the contact owns a 2018 GMC sierra 1500. The contact stated that while driving at various speeds, the temperature gauge indicated that the vehicle was overheated. No warning light was illuminated. The vehicle was taken to beck & masten Buick GMC north (11300 fm 1960 west, houston, tx 77065, (877) 380-8433) where it was diagnosed and determined that the radiator was leaking coolant and that…
Had engine trouble with your 2018 GMC Sierra?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the engine problem on the 2018 GMC Sierra?
It's a documented issue but not catastrophic. 39 complaints have been filed. Repairs average $3,100 and most owners catch it before it causes a breakdown.
At what mileage does the engine typically fail?
Across the 19 complaints that reported odometer mileage, most engine failures cluster between 42,000 and 90,000 miles, with the median around 59,000. A quarter of owners report trouble before 42,000; a quarter make it past 90,000. Maintenance history matters more than the odometer alone — this is the reported failure window, not a guarantee.
What does it cost to fix?
Independent shops typically charge around $3,100 for engine repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to engine?
No active recalls currently cover engine issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2018/GMC/Sierra.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.