GM used defective engine cylinder heads for millions of 4.8/5.3 liter V8 engines from 2001-2006. The cylinder heads crack causing coolant to flow into the oil and cause excessive sludge to form and cause engine failure. GM knows about the problem and issued tsb to it's service departments:1 information on gradual coolant loss over time with no evidence of leak found #06-06-01-019B - (06/12/2007). These defective cylinder heads can cause overheating and complete engine failure.

- Keller, TX, USA

Cylinder heads are leaking coolant into the engine. This causes excessive lifter noise when first started after the engine has been sitting for several hours and requires coolant to be added almost daily. This condition will eventually ruin the engine requiring the engine to be replaced. This problem is known by GM to be a defect in the casting process, yet no help is offered by GM to fix the problem.

- San Ramon, CA, USA

The contact owns a 2004 Chevrolet Tahoe. The contact stated that there was a cooling fluid leak, and she had to add cooling fluid consistently. The vehicle was taken to a private mechanic, who stated that there was cooling fluid leaking into the oil pan in the engine. The failure was reported to the manufacturer who acknowledged there was a technical service bulletin, but refused to provide assistance for the repair. The failure mileage was 84,000. The current mileage was 86,000.

- Kalamazoo , MI, USA

Engine started with a ticking noise when cold. Would go away after engine warmed up. Upon inspection found 2 exhaust manifold bolts sheared on #7 cylinder, 1 broken on #8. ticking coming from exhaust leak on #7. upon research found that this is a common issue with these engines. Why is there no recall or safety notice as it presents a real hazard for fire and exhaust fumes entering passenger compartment.

- Amelia, OH, USA

The contact owns a 2004 Chevrolet Tahoe. The contact stated that the cylinder heads fractured on the vehicle and the engine overheated. The contact had the vehicle inspected by a mechanic and it was found that coolant leaked into the engine. The contact was told that if this continues the engine will eventually fail. The vehicle was not repaired. The VIN was not available. The failure mileage was 115,000 and the current mileage was 117,000.

- Lakewood, CO, USA

I started having problems with my 2004 Chevy Tahoe is September 2009 when the vehicle only had 71,000 miles. The vehicle was using a lot of oil and I took it to the dealership and they notified me that their was no oil leaks and performed a compression test. Since that date I have needed to add additional oil in between oil changes. In the last couple of months it started to use a lot of coolant. I have added about 4 gallons of coolant in the past two months. I took the vehicle to the dealer and was notified that the left cylinder head was leaking coolant in the engine. After further research I found that the castech heads in this model were porous which caused them to crack. The dealer is recommending that the engine be replaced at a cost of $6400. I feel Chevy should be responsible for this repair since they are aware that the problem has to do with the castech heads.

- Fallbrook, CA, USA