This service bulletin provides information for maintenance cleaning of the fuel injectors and gasoline detergent additive.
full bulletin at NHTSA ↗2007 Hummer H3 engine problems
moderate 31 complaints filed with NHTSA · avg repair $3,100 · see engine across all vehicles →
Failure mileage
Complaints
31
Recalls
0
Avg fix
$3,100
1fire
When does it fail?
Of the 31 engine complaints filed for the 2007 Hummer H3, here's the actual mileage breakdown — failures cluster heaviest at 50,000-75,000 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 31 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 11 years — the issue may be aging out of the active population.
Is there a fix? Manufacturer service bulletins
The manufacturer has issued service bulletins covering engine on this vehicle — documented repair instructions, service campaigns, or warranty extensions sent to dealers. A TSB isn't a recall (it's not a free safety remedy), but it's the manufacturer acknowledging the issue and how to fix it.
This bulletin provides information on identifying Non-GM Engine Calibrations for Gasoline Engines using the Tech 2 or GDS 2.
full bulletin at NHTSA ↗This service bulletin provides guidelines and diagnostic/repair information to technicians regarding vehicle engine oil consumption.
full bulletin at NHTSA ↗This service bulletin provides technicians with information to help identify the differences between what is considered a fluid leak, and what is considered fluid seepage.
full bulletin at NHTSA ↗This technical bulletin advises of a new fuel injection cleaner kit used for decarbonizing the intake valves to correct conditions of rough idle, Crank no start, extended crank or misfire, MIL with DTCs, and explains how Top Tier fuels should be used to reduce carbon build-up.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
Owners of 2007 H3s describe cascading engine and cooling system failures that start early and recur often. The plastic radiator upper tank is the most consistent problem—hairline cracks appear at 50,000 to 100,000 miles, sometimes without any rough use, causing rapid coolant loss. Mechanics at one shop reported seeing six cracked H3 radiators in six months. Replacement runs $1,000–$1,100 and requires AC system discharge because the receiver drier must be disconnected.
Engine stalling is the second major complaint. The engine shuts down unexpectedly at low speeds—on mountain roads, in town, at traffic lights—sometimes causing loss of power steering and near-accidents. One owner documented RPM fluctuations on video before shutdown; dealers repeatedly claim they cannot reproduce the issue. Cold starts and mornings seem to trigger it more often.
Beyond radiators and stalling, owners report manifold cracks or gasket failure (exhaust fumes in cabin, burned oil), cylinder head valve seal leaks (reduced power, misfires, shaking), PassLock security system start failures (crank but no-start, then works after 10-minute wait), and catastrophic failures like engine fire and metal shavings in oil. Five attempts to diagnose and repair stalling under warranty yielded no fix. One case involved transmission destruction when the radiator failed and coolant contaminated transmission fluid.
Dealer response has been inconsistent—some refuse to service vehicles once warranty expires, others cannot reproduce intermittent issues in the shop, and some acknowledge the plastic radiator is a known defect but no recall has been issued.
Same Hummer H3 engine reports on nearby years: 2006 · 2008
Failure modes owners describe
Plastic radiator hairline cracks and leaks
Plastic upper tanks on the radiator develop hairline cracks at low mileage, often in the 50,000–100,000 mile range, causing coolant leaks. Multiple owners report this as a well-known, recurring issue with H3s from 2006–2009. The cracks occur without trauma or rough use. One owner reported a mechanic shop seeing six cases in six months. Radiator replacement is expensive—one owner paid $966.57, another was quoted $1,100—because the AC receiver drier must be disconnected, requiring refrigerant discharge and recharge.
When: 50,000–100,000 miles; one failure at 65,370 miles
Symptoms owners cite: Coolant smell (vaporizing); Coolant leaks beneath vehicle; Coolant blown into engine compartment; Temperature gauge normal despite leak
Repairs/costs cited: Radiator replacement: one quoted at $1,100 with 2-year/24,000-mile warranty on replacement plastic radiator; one owner paid $966.57 including AC service. Repair requires AC system discharge and recharge.
Recalls/TSBs owners mention: NHTSA campaign 15V421000 mentioned (visibility-related); one owner reported manufacturer would 'participate' in repair costs if diagnosed as manufacturer defect; one owner states no recall issued despite widespread problem.
Engine stalling at low speed
Engine shuts off while driving at speeds between 0 and 50 mph, often without warning. Stalling can happen on mountain roads, at traffic lights, at gas stations, or during initial morning drives. One owner lost power steering three times on mountain cliffs due to stalling. Another reported stalling four times over 70,000 miles with dealer unable to reproduce. Video evidence from one owner shows RPMs fluctuating erratically before shutdown, followed by repeated restart failures over 15 minutes before normal operation resumes. Stalling is more common in cold weather and mornings.
When: Intermittent; often at startup or during first drive of the day; one case at ~70,000 miles
Symptoms owners cite: Sudden engine shutdown at low speed; Loss of power steering; RPM fluctuations (up and down) before shutdown; Repeated restart failures followed by brief operation; More frequent in cold/snow conditions; Lingers 15 minutes then resolves
Repairs/costs cited: One owner had five attempted 'repairs' under warranty with no success; dealers unable to reproduce issue in shop.
Engine fails to start—PassLock security system malfunction
Engine cranks normally but will not start, then starts reliably after a 10-minute wait. One owner identified a pattern: security light blinking on dashboard indicates no-start condition; steady light means normal start. Failure can occur at any time—at gas stations, first thing in the morning. One owner replaced manifold and was reimbursed by manufacturer; another had anti-theft light illuminate during intermittent start failures.
When: Intermittent; one case at 84,822 miles; another at 74,000 miles
Symptoms owners cite: Engine cranks but does not start; Security/anti-theft light blinking or illuminated; Starts normally after ~10 minutes wait; Occurs unpredictably, becoming more frequent
Repairs/costs cited: One owner replaced manifold out of pocket, was reimbursed; another waited 10 minutes between attempts.
Recalls/TSBs owners mention: One owner reports manufacturer was notified and owner was reimbursed for manifold replacement.
Engine overheating and coolant loss
Vehicle overheats while driving, triggering check engine light. Coolant leaks rapidly—one owner refilled coolant, and it leaked dry within 4 hours despite light driving and no AC use. Another owner's coolant tanks were empty the morning after refilling. One case involved coolant mixing with transmission fluid when radiator failed, destroying the transmission. Thermostat replacement did not resolve recurring failure in one case.
When: One case at 136,000 miles; one at early 2008 (2007 model); one at low mileage; one at ~56,800 miles
Symptoms owners cite: Vehicle overheats while driving or at stop; Check engine light illuminates; Rapid coolant loss; Coolant leaking from radiator area
Repairs/costs cited: One case: speed sensor replaced (did not resolve); thermostat replaced (failure recurred). One case: transmission destroyed due to coolant/transmission fluid mixing.
Exhaust manifold issues—cracks and gasket failure
Exhaust manifold develops small holes or cracks, burning oil and emitting odors, or manifold gasket fails, allowing exhaust fumes to enter the cabin. One owner reported a small hole in the manifold at 120,000 miles burning out oil. Another reported white steam from the engine at 40 mph and cracked radiator seal (possibly manifold-related). A third experienced exhaust fumes filling the vehicle at 50 mph, requiring manifold gasket replacement.
When: 120,000 miles (hole); 65,370 miles (steam/seal); 160,000 miles (gasket); one at 84,822 miles (manifold replaced)
Symptoms owners cite: Burning oil smell; White steam emitting from engine; Exhaust fumes inside cabin; Oil indicator illuminated
Repairs/costs cited: One owner paid out of pocket for manifold repair at 120,000 miles; one had manifold gasket replaced; one owner replaced manifold and was reimbursed by manufacturer.
Recalls/TSBs owners mention: One case: manufacturer notified and claim filed; one case: manufacturer notified.
Cylinder head valve seal failure
Valve seals in cylinder heads fail, causing loss of acceleration power and performance loss. One case involved 70% leakage in valve seals of the second and fifth cylinder heads, with the fifth head being the primary cause. Another owner experienced frequent misfires, engine nearly stalling at idle, and vehicle shaking, with multiple complaints online about cylinder head replacement requirements.
When: 65,000 miles (dominant failure in fifth cylinder head)
Symptoms owners cite: Loss of acceleration power; Frequent misfires; Engine nearly stalls at idle; Vehicle shaking/vibration; Lack of power and efficiency; Juddering while accelerating
Repairs/costs cited: One case: both cylinder heads had 70% leak and were identified as needing replacement; cylinder head replacement cost 'hundreds at a minimum' per owner reports.
Engine mechanical failure—stalling, rough operation, metal shavings
Engine stalls and dies at various times without warning or indication, sometimes in dangerous situations like intersections. One owner found metal shavings in oil, suggesting internal engine wear or damage. Another case involved violent shaking and stalling at 40 mph; dealer diagnosed need for engine or cylinder replacement but vehicle was not repaired.
When: 56,800 miles (violent stall); mileage unknown for others
Symptoms owners cite: Sudden stalling and shutdown while driving; Metal shavings in oil; Violent shaking before stall; No warning or indication before failure
Repairs/costs cited: One case: dealer diagnosed engine or cylinder replacement needed but owner did not repair; no repair costs cited.
Engine fire—electrical or ignition source
Engine fire originated behind glove compartment area, with smoke and flames observed while vehicle was parked at a gas station. Fire department and police responded. Owner moved vehicle away from fuel pumps to prevent explosion.
When: Occurrence during brief stop at gas station
Symptoms owners cite: Burning smell; Smoke rolling from engine compartment; Fire behind glove compartment
Repairs/costs cited: No repair details provided.
Synthesized from 31 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 5 most recent
Tl* the contact owns a 2007 Hummer h3. While driving approximately 40 MPH, the vehicle shook violently and stalled without warning. The vehicle could not be restarted. The vehicle was towed to the dealer where it was diagnosed that the engine or the cylinder needed to be replaced. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was 56,800.…
Tl* the contact owns a 2007 Hummer h3. While driving 35 MPH, the engine oil indicator illuminated and an odor emitted from the vehicle. The contact replaced the oil and took the vehicle to an independent mechanic where it was discovered that there was a small hole in the manifold, which burned out the oil. The contact paid out of pocket to have the vehicle repaired. The manufacturer was notified…
Noticed radiator fluid dripping underneath vehicle. Opened the hood and found radiator coolant had been blown all over interior engine compartment. Enough coolant remained in the reservoir to prevent overheating. I noticed the incident just in time. *tr
Driving down the road and it stop and it would not start engine lock up
If returning soon after shut off ; it will not restart. Have to wait awhile for it to restart. It's weird because there are no other problems. It has been doing this for awhile now.
Had engine trouble with your 2007 Hummer H3?
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 2007 Hummer H3?
It's a documented issue but not catastrophic. 31 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 28 complaints that reported odometer mileage, most engine failures cluster between 59,614 and 120,000 miles, with the median around 73,550. A quarter of owners report trouble before 59,614; a quarter make it past 120,000. 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/2007/Hummer/H3.
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.