Hey guys...I've decided to come to the experts here and see if someone can give me any info. I have an 02 Olds Bravada (same drivetrain as the Trailblazer, Envoy and Rainier). It has the 4.2 I6, approx 60K miles. Oil changed 3K miles with 5w/30 dino oil. Recently, in the last few thousand miles, I've noticed what sounds like a lifter knock, esp when cold or under "heavy" loads, like towing my 3500# camper. When it first started I immediately changed the oil and filter eventhough it wasn't 3000 miles yet thinking that it might help. No luck. In desperation, I added a can of Sea Foam to "quiet" things down...didn't work...now I'm concerned about having to do some major engine work. I already have to rebuild the 350 in the LeSabre...I don't want to have to do it here too. Suggestions? I really hate taking it to the dealer, but it might be my only shot. Up until this, it was very difficult to hear the engine running it was so smooth and quiet. And overall, it's a great truck.
Those motors are known for having as much piston slap as an LS1. Sounds like lifter tick, but it's the pistons slapping in their bores. Fairly common on GM engines with the "skirtless" piston design. My father's '02 Trailblazer needed a piston sleeve replaced at 5k miles, had a bad knock/tick and eventually had head sealing issues. GM warrantied it after a lot of fighting considering the truck was 4 years old with only 5k miles.
