I own a 2004 GMC Sierra 1500 that is currently being repaired for cracks in both engine heads. The truck has 90,000 miles on it and I have kept up on all necessary maintenance. The problem began approx. 2 months ago when I noted a knocking sound after starting the truck cold. The knocking would dissipate after the truck warmed up. I was told the sound was caused from dirty lifters and not to be concerned as long as sound dissipated after it was warm. Upon having my oil changed 2 days ago, coolant was noted in the oil. (hints the knocking) the heads were pulled and both were cracked around where the heads bolt to the block. In talking to the mechanic, the cast they used when making the heads was bad. Apparently around the bolt holes, the aluminum is thin. GMC however accepted millions of these and are still using them today. The repair is costing me $3,400.

- Mather, CA, USA

Engine failure 2004 GMC Sierra service bulletin 06-06-01-019B internal coolant loss leak in cylinder heads mfg by costech lead to my engines death with just 89,000 miles. This is a know problem since 2004 and from other people I have learned GM will not cover expenses.

- Hopkinton, MA, USA

Reduced engine power, this has happened about 7 times. When this happens the engine shuts down to 1500 rpms maximum. Took to dealer, they told me that it was the throttle body valve and actuator assembly. This part was replaced at a cost of $481. Within two weeks the same problem has happened twice more. This is dangerous when traveling in traffic.

- Adair, OK, USA