Which parts fail
Components named in complaints (engine, cooling system, oil leaks, timing chain, exhaust).
Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2008 Hummer H3 owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2008 Hummer H3. The contact stated that the vehicle intermittently failed to start up without warning. The contact stated that after waiting ten minutes the vehicle started. The contact stated that recently the failure had become more frequent. The contact had taken the vehicle to a dealer however, the mechanic was unable to determine the cause of the failure. The manufacturer was not notified of the failure. The vehicle was not repaired. The failure mileage was approximately 1,000.
Engine was replaced at 163,000 miles now at 168,000 miles the frame is rusted beyond repair and is about to give at any moment nothing really left near rear axels. This could have definitely caused a horrible accident to myself or others having a big car just give way and collapse. Took it to mechanic who warned me first then next day took it to body shop that said nothing could be done. Basically both said get rid of it for parts as fast as you can and don't look back. After the body shop guy actually showed me the rusted out areas i was scared to even drive it like the 10miles back to my house. It sucks after spending all that money on an engine and now having this issue and now having to buy a new car.
The contact owns a 2008 Hummer H3. The contact stated that while driving at various speeds, an abnormal knocking sound was coming from the engine. The check engine warning light was illuminated. The contact stated that the failure worsened while driving at highway speeds. The contact called the dealer and the manufacturer and notified them about the failure. The contact was informed by both that there were no recalls on the vehicle. The vehicle was not repaired. The failure mileage was unknown.
The last dealership I went to they advised to come th the dealership but when I got there nobody wasn't trying to work there instead the said that it was going to be hard to work on it cause nobody work on those cars anymore and then they said they were going to order the part but never call me back for it. Call them but gave me the runaround basically.
exhaust leaking in cab of the car .Exhaust bolts broke or manifold cracked problem i heard about on line .on a long trip could make you passout with the fumes .please check it out .on most inline 5 cyclinder engines GM makes .Thank you [redacted]
Radiator has a 8 inch horizontal hair line crack that lets the coolant leak. The crack is on top right corner( drivers side). The radiator top is made from plastic that is prone to cracking due to framework bumping into it causing strain on radiator top which after time causes the top right corner to establish a hairline crack and cause the coolant to leak. Many Hummer H3 vehicles owners have complained about this issue of having hairline cracks in top right corner. Hummer has replaced several Hummer owners radiators at no cost, due to a design flaw that the top right radiator bumps into the framework causing stress on it and cracking. GM has updated the radiator to accommodate for this issue, but has not showed interest in saying that this is a big issue. Why would they allow this to happen to thousands of Hummer H3 owners if they know this is a design flaw which they are aware of. …
The security lock system on my Hummer H3 intermittently flashes during start causing the vehicle to not crank. Normally I have to wait 10 to 20 minutes for the system to reset itself and she starts right up, but today it's been 8 hours. Finally I had to call for a tow to the GM dealership. We got lucky today. At 10 am my wife thought she was going into labor, we get to the truck and no start. Just a flashing security lock symbol flashing at me. Ended up using her car. This is definitely a safety concern, what if her water had broke or my son was needing medical attention. I know GM knows of this defect because I have read thousands of complaints about this exact problem online. They will not fix it unless made to.
The antilock safety is preventing me from starting my vehicle. When it does start, and I go to an intersection to turn the truck will then stall out. It can cause a wreck. It is a huge safety issue, time consuming, and money consuming when I have to wait 10 minutes to try to start my truck, or it doesn't start, I have to replace it for $450+ which I don't have to replace the ignition switch and it's dangerous because if it does let it start I have to be careful because it will stall out on any given second causing a catastrophe!!! There are multiple people with the same issues on their vehicles. GM should be responsible to do a recall and fix this problem.
Tl* the contact owns a 2008 Hummer H3. While driving 45 MPH, the temperature gauge displayed that the vehicle's temperature was very high. The contact merged to the side of the road and poured antifreeze into the vehicle. The failure recurred numerous times. The vehicle was taken to a dealer. The technician diagnosed that the radiator had fractured and needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure. The failure mileage was 74,000. The VIN was unavailable. ...updated 08/10/15
Tl* the contact owns a 2008 Hummer H3. When the vehicle was taken to be serviced for NHTSA campaign number: 15V421000 (visibility), the technician discovered that two bolts located on the exhaust manifold were fractured. As a result, carbon monoxide was leaking inside the vehicle. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 54,000.
Engine complaints in other H3 years
Frequently asked questions
How common are engine problems on the 2008 Hummer H3?
NHTSA has 22 complaints about the engine & cooling of the 2008 Hummer H3, 19% of the model year's 113 complaints. The component named most often is exhaust system › manifold/header/muffler/tail pipe (1 mentions).
Is there a recall for 2008 Hummer H3 engine problems?
No. NHTSA lists no engine & cooling recall for the 2008 Hummer H3, though it has 2 recalls for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2008 Hummer H3 engine problems start?
Half of the complaints with a recorded mileage happened before about 74,000 miles, and 13% before 25,000 miles.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.