Attention: TDR Forum Junkies 
Read this from Yesterday's Oregonian about Silent Fixes on GM's new gas engines (99-02).
11/22/03
JOCELYN PARKER
General Motors Corp. is quietly buying back from customers some of its priciest light trucks, including the GMC Yukon and Chevrolet Silverado, because of loud knocking noises in their engines. Thousands of vehicles, most from the 1999 to 2002 model years, may be affected.
Some experts say the knocking, caused by contact between the engine's pistons and cylinders, might prove damaging in the long run.
GM acknowledges the problem but denies that it causes damage and has resisted a nationwide recall. The company, which said the problem surfaced when it moved to a new family of engines, says it does not affect engine performance and that it was corrected in later-model vehicles.
The problem is, there's no apparent fix for the earlier models, leaving some buyers angry and worried. "I paid almost $35,000 for this truck. The truck is almost worthless," said Greg MacNeil, who purchased his 2001 Chevrolet Silverado two years ago. "In good conscience, I couldn't sell this truck to someone else. "
Ron Martiny of Oshkosh, Wis. , said he had just driven home from Florida in February 2002 when his Silverado's engine started knocking, too. His dealer told him the sound was normal. But a month ago, GM bought back his $40,000 truck, he said.
It's unclear exactly how many vehicles or how many kinds of GM vehicles have this noise, but customers and several lemon law lawyers say the problem occurs within months after customers drive them off dealer lots.
Lemon law lawyers say they occasionally get calls about engine knock with other automakers' vehicles, but they report an unusually high incidence of this kind of problem with GM vehicles.
"In the last year, this problem became really obvious," said Brian Parker, a Michigan lemon law attorney.
According to GM dealer service bulletins, vehicles with the engine knock include 1999 through 2002 Chevy and GMC pickups and sport-utility models with 4. 8-, 5. 3- and 6. 0-liter V8 engines.
The bulletins say the noises are not detrimental to the vehicles, but some experts say knocking is abnormal and can damage the engine.
Dan Powell, who lives near Orlando, Fla. , and owns a 2001 Yukon XL with an engine knock, was so incensed by the knocking that he created a Web site, www.pistonslap.com, that discusses the engine problem and seeks feedback from others with the issue. Powell is also suing to get his money back for the vehicle.
GM spokesman Tom Read said the company is working with angry consumers on a "case-by-case basis. " Read wouldn't comment on any litigation but said the knocking affects only "a small percentage of vehicles. "
Read also wouldn't confirm or deny that the company is offering warranties, cash offers or buybacks for the vehicles.
What a consumer gets for the problem really depends on how hard they're willing to fight, lawyers say.
A lawsuit is generally the only way GM will buy the cars and trucks back, Martiny's attorney, Vince Megna, added. "GM has always bought the vehicle back, but only after being pushed," he said.
Clarence Ditlow, executive director for the Center for Auto Safety, said GM's stance on the issue is not surprising because repairing all those vehicles would cost millions of dollars. And if the defect doesn't cause a safety or emissions issue, it's tough to get a national recall.
The National Highway Traffic Safety Administration says it doesn't track these sorts of problems because they aren't safety-related.
Carbon buildup
GM officials say carbon and the amount of clearance between the piston and the cylinder wall are the primary causes of the knocking.
Usually, when the piston moves up and down in the cylinder, a component called the ring land, which is near the top of the piston, does not come in contact with the cylinder wall. But when carbon forms on the ring land over time, the ring land gets wider and begins to hit the wall. When the two come in contact, the driver will hear the knocking noise, said Chris Meagher, assistant chief engineer for GM's small block V8 engines.
Spacing is also an issue, because when there's too much room between the piston and the cylinder wall, a greater amount of rocking can occur and can cause more noise, experts say.
Read said GM has addressed the issue by making design changes to the piston in some 2002 vehicles and all 2003 vehicles with the noise. GM has cut the amount of space between the piston and the cylinder so that the amount of rocking is reduced. The changes also keep the ring land from contacting the cylinder wall when carbon builds up, Meagher said.
Read said the knocking issue came about when GM started making a new family of truck engines in 1999. The company, however, vows that the knocking won't cause any damage to the engine because the carbon that has formed on the ring land isn't hard enough to damage the cylinder wall.
"Current analysis of 150,000 mile- and 300,000 mile-engines that have exhibited cold start noise show no significant wear," Read said.
While it remains unclear whether the knocking causes damage, lawyers and consumers say the piston's contact with the cylinder wall can't be good.
Knocking, for instance, has been known to cause damage to the piston, and in some cases it has resulted in premature engine wear.
Regardless, consumers, many of whom are loyal GM customers, say they're disappointed that there isn't a repair for the problems.
"I would love to have it fixed if they have a fix," Powell said. "Except for the engine, it's a nice vehicle. "
And despite the controversy, GM's trucks got high marks in J. D. Power and Associates' 2003 reliability and dependability surveys. The Silverado, for instance, ranked second in initial quality in the study's full-size pickup category.
11/22/03
JOCELYN PARKER
General Motors Corp. is quietly buying back from customers some of its priciest light trucks, including the GMC Yukon and Chevrolet Silverado, because of loud knocking noises in their engines. Thousands of vehicles, most from the 1999 to 2002 model years, may be affected.
Some experts say the knocking, caused by contact between the engine's pistons and cylinders, might prove damaging in the long run.
GM acknowledges the problem but denies that it causes damage and has resisted a nationwide recall. The company, which said the problem surfaced when it moved to a new family of engines, says it does not affect engine performance and that it was corrected in later-model vehicles.
The problem is, there's no apparent fix for the earlier models, leaving some buyers angry and worried. "I paid almost $35,000 for this truck. The truck is almost worthless," said Greg MacNeil, who purchased his 2001 Chevrolet Silverado two years ago. "In good conscience, I couldn't sell this truck to someone else. "
Ron Martiny of Oshkosh, Wis. , said he had just driven home from Florida in February 2002 when his Silverado's engine started knocking, too. His dealer told him the sound was normal. But a month ago, GM bought back his $40,000 truck, he said.
It's unclear exactly how many vehicles or how many kinds of GM vehicles have this noise, but customers and several lemon law lawyers say the problem occurs within months after customers drive them off dealer lots.
Lemon law lawyers say they occasionally get calls about engine knock with other automakers' vehicles, but they report an unusually high incidence of this kind of problem with GM vehicles.
"In the last year, this problem became really obvious," said Brian Parker, a Michigan lemon law attorney.
According to GM dealer service bulletins, vehicles with the engine knock include 1999 through 2002 Chevy and GMC pickups and sport-utility models with 4. 8-, 5. 3- and 6. 0-liter V8 engines.
The bulletins say the noises are not detrimental to the vehicles, but some experts say knocking is abnormal and can damage the engine.
Dan Powell, who lives near Orlando, Fla. , and owns a 2001 Yukon XL with an engine knock, was so incensed by the knocking that he created a Web site, www.pistonslap.com, that discusses the engine problem and seeks feedback from others with the issue. Powell is also suing to get his money back for the vehicle.
GM spokesman Tom Read said the company is working with angry consumers on a "case-by-case basis. " Read wouldn't comment on any litigation but said the knocking affects only "a small percentage of vehicles. "
Read also wouldn't confirm or deny that the company is offering warranties, cash offers or buybacks for the vehicles.
What a consumer gets for the problem really depends on how hard they're willing to fight, lawyers say.
A lawsuit is generally the only way GM will buy the cars and trucks back, Martiny's attorney, Vince Megna, added. "GM has always bought the vehicle back, but only after being pushed," he said.
Clarence Ditlow, executive director for the Center for Auto Safety, said GM's stance on the issue is not surprising because repairing all those vehicles would cost millions of dollars. And if the defect doesn't cause a safety or emissions issue, it's tough to get a national recall.
The National Highway Traffic Safety Administration says it doesn't track these sorts of problems because they aren't safety-related.
Carbon buildup
GM officials say carbon and the amount of clearance between the piston and the cylinder wall are the primary causes of the knocking.
Usually, when the piston moves up and down in the cylinder, a component called the ring land, which is near the top of the piston, does not come in contact with the cylinder wall. But when carbon forms on the ring land over time, the ring land gets wider and begins to hit the wall. When the two come in contact, the driver will hear the knocking noise, said Chris Meagher, assistant chief engineer for GM's small block V8 engines.
Spacing is also an issue, because when there's too much room between the piston and the cylinder wall, a greater amount of rocking can occur and can cause more noise, experts say.
Read said GM has addressed the issue by making design changes to the piston in some 2002 vehicles and all 2003 vehicles with the noise. GM has cut the amount of space between the piston and the cylinder so that the amount of rocking is reduced. The changes also keep the ring land from contacting the cylinder wall when carbon builds up, Meagher said.
Read said the knocking issue came about when GM started making a new family of truck engines in 1999. The company, however, vows that the knocking won't cause any damage to the engine because the carbon that has formed on the ring land isn't hard enough to damage the cylinder wall.
"Current analysis of 150,000 mile- and 300,000 mile-engines that have exhibited cold start noise show no significant wear," Read said.
While it remains unclear whether the knocking causes damage, lawyers and consumers say the piston's contact with the cylinder wall can't be good.
Knocking, for instance, has been known to cause damage to the piston, and in some cases it has resulted in premature engine wear.
Regardless, consumers, many of whom are loyal GM customers, say they're disappointed that there isn't a repair for the problems.
"I would love to have it fixed if they have a fix," Powell said. "Except for the engine, it's a nice vehicle. "
And despite the controversy, GM's trucks got high marks in J. D. Power and Associates' 2003 reliability and dependability surveys. The Silverado, for instance, ranked second in initial quality in the study's full-size pickup category.
