Q: My 2006 Chevy Colorado pickup has developed a misfire. I took it to a shop. They ran some tests and said it has low compression due to a faulty intake valve. They said this was common for this truck. I'm pondering my options, as it's a shame to give up on this truck with only 72,000 miles on the odometer. What are your suggestions for what to do?
A: Ed, you're correct this is a common fault on GM's 2.8- and 3.5-liter engines built from 2004 to 2006. The intake valve seats deteriorate and compression is lost. In 2008, GM offered a special coverage adjustment, extending the warranty period for a failure of this type to seven years or 100,000 miles. Unfortunately, you are far beyond the time frame.
All is not lost. A valve job should get your Colorado running sweet again! The cylinder head is removed and either replaced with an exchange unit or remanufactured by a local machine shop. A lower timing gear tensioner holding tool saves time during disassembly/reassembly, and the job can be performed with the engine remaining in the chassis.
It's prudent during a job like this to also consider renewing belts, hoses, water pump and a few other miscellaneous parts along with the cylinder head work. Remanufactured/exchange cylinder heads run about $700 and the labor to do the job is perhaps 10-12 hours. Not an inexpensive repair, but it pales in comparison to buying another truck!
Q: My son's car has begun to overheat at times. I'm trying to get him to get it serviced before he destroys the engine. Can you provide me with some causes and ammunition to get him moving on this?
A: This needs prompt attention! A head gasket failure, damaged cylinder head or worse can result, costing several thousand dollars! If the engine is losing coolant due to a leak, the cause should be fairly evident, and perhaps not that difficult to resolve. Common leakage causes are failed hoses, loose connections, a leaky water pump, or heater core (leaks inside the cabin).
When does the high temperature condition occur? If at low speed/in traffic, an inoperative electric cooling fan could be the cause. Can he hear the fan cycling on at times? On longitudinal engines (inline) the mechanical fan likely includes a fan clutch to increase airflow under high temperature conditions. This may be faulty.
At high speed/load, the cause could be a restricted radiator (bugs or debris clogging exterior, and/or the air conditioner condenser in front of the radiator, or clogging interior passages), a missing or damaged air deflector (which directs air to the radiator) or a worn water pump impeller, among other possibilities.
Your son can improve the chances for an accurate diagnosis and repair if he can explain or demonstrate the symptom to the service provider.
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at email@example.com; he cannot make personal replies.
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