Busted Piston

[Rooftop Rocket]

Anyone heard of this happening?

Bought an 07 Yukon Denali 6.2L with 169,000 miles from a used car lot. Getting up in the miles, but it was almost perfect condition inside and out. Which made us believe it was probably an older owner who just put highway miles on it.

Engine didn't make a noise until the day after purchase. After research, we decided it was the common lifter tick.

3 weeks after purchase, I had to get on it to get into a break in traffic. It makes a clunking sound and starts knocking.

We assume the worse and have it towed home, but it will start and run. Just doesn't sound too good. Thinking its a collapsed lifter, we order a set of LS7's and start taking the motor apart.

What we found was way worse. The #6 piston had apparently just broke apart and chewed up the top of the piston and bottom of the head.

Also, the valves are fine, not even bent. Only thing we can come up with, is the piston merely started breaking apart.

So now, we're on eBay searching for parts. Just wondering if anyone else has seen or even heard of this happening?

Thanks

 

[Wake]

The only time I've ever seen anything like that was when the engine sucked something in. I wonder if someone had it apart before and a loose screw, nut, bolt found its way into the intake or head. It doesn't look to me like the piston broke apart and did that. It just looks like it was beat up from something being inside the combustion chamber.

Maybe take a look down the exhaust to see if anything is in there, the cat should stop it from being blown out.

 

[Rooftop Rocket]

Thanks Wake, we also considered that same possibility, but we had been driving it for 3 weeks. Surely it would have fell in way before that wouldn't ya think? Anything is possible though.

 

[about20ninj45]

Thanks Wake, we also considered that same possibility, but we had been driving it for 3 weeks. Surely it would have fell in way before that wouldn't ya think? Anything is possible though.

Studying those pics, is that water inside of your engine?

 

[Rooftop Rocket]

Studying those pics, is that water inside of your engine?

Yes, I wasn't sure how to drain the engine coolant completely before removing the head. Most came out, but still had a little left, even after removing the radiator. The pic was taken immediately after head removal, before the excess coolant was cleaned up.

 

[about20ninj45]

If you disconnected the the lower radiator hose and run the engine before dissassembly, you would pump out all the fluid. Make sue you shop vac all those liquids out or you risk hydrolocking the motor after you fix it. To fix that engine, you might also want to disassemble that connecting rod and check the bearings caps. It could have been that the bolts holding the caps on the connecting rod were loose causing the piston to come in contact with the heads, while the valves were closed.

 

[Wake]

Thanks Wake, we also considered that same possibility, but we had been driving it for 3 weeks. Surely it would have fell in way before that wouldn't ya think? Anything is possible though.

Not necessarily. It could have been hung up inside the intake or head until it finally worked itself loose. To me it looks like something was in there and I don't see anything missing in your pic.