2009 Chevrolet 1500 w/ 4.8L bent valve. Only 65,000 miles

[ryan_jdsales]

My Dad was driving on interstate with cruise control set at 78 mph and all of sudden engine started making noise and dash lit up like Christmas tree. Pulled over and noticed miss and limped 5 miles back to GM shop. Codes pulled were #5 and #7 hard miss. They pulled valve cover, checked valves and said engine had burned up valves. He called and wanted to bring home (3 hrs away) so I hauled home on trailer. Rechecked their diagnosis and found that when applying air to #5 cylinder, had bad leak to exhaust. Disassembled figuring valve had burnt, and found when pulled head that #5 exhaust valve was bent and had minor contact with piston. Could barely catch w/ fingernail where valve contacted piston. Not sure why #7 set a code, nor why exhaust valve is bent on #5. Anyone have any ideas of why this happened? I did not pull head on RH side of engine to see if there was any damage.

[Jsdirt]

The #7 probably threw a code due to the violent hammering of #5.

 

I chalk this up to shoddy manufacturing practices at the factory - either substandard metals, or half-assed assembly. We've been building engines for over 100 years now - this type of failure is inexcusable.

[Doug_Scott]

Are these engines interference engines? If so, then you will want to verify that the cam timing is still correct. You have a chicken/egg issue here and need to determine source of bent valve. Are there any marks on the valve face or seat? How was the head gasket between cylinder 5 and 7?

[ryan_jdsales]

I do not know if the 4.8 is an interference engine, however, no other valves touched piston on LH side and I pulled all plugs on RH side and all were in perfect shape. Had I seen other evidence of valves touching Pistons I would've pulled timing cover to check. The head gasket appeared to me to be in perfect shape. I did not see any valve seat or face damage ruling out foreign object in cylinder. I've done a lot of head gasket analysis on Deere Ag engines, so I would hope I know what I am looking at, but this is the 1st gas engine I've been in for probably 10 years. It appears that valve may have stuck, since it does not move freely in bore and then piston bent the head on it. These valves are a lot smaller than what I am used to working with, so am assuming they are more touchy to sticking and it does not take much contact to bend.

[Jsdirt]

Wouldn't surprise me if they stuck - that's just basic machine shop cleanliness issues right there - a shred of metal in the valve guide, probably. Or maybe a lifter hung up in similar fashion. Anything's possible today.

 

I would bet on these engines being an interference design. GM wouldn't want you to fix it yourself when the 10-speed-bicycle-sized chain snaps in 2.

[Doug_Scott]

If the valve did stick, you should be able to see why once you remove the valve. Do not spray any solvents on it trying to remove that valve though, you may just wash off any crud on the stem. Ever get one of those days where you just cannot think of the right word? Crud is the only word I can come up with. I am talking about that crap that oil leaves behind when it is dirty and gets cooked onto metal surfaces.

 

Sticking valves is not that common from what I have been reading online. Take a good look at the lifters and lifter bores as well. Check for any bent push rods too. Interference engines do not normally only bend one valve when cam timing goes out. They will bend at least one valve per cylinder, unless you happen to have the engine seize or stop dead after first contact.

[Jsdirt]

Sludge.

 

Yeah, at the very least they'd hit the 4 that were near the exhaust / intake strokes at the time. I'd have to think the momentum of a V8 would carry it around to smash them all, even at idle.

 

Odd problems cropping up these days!

[ryan_jdsales]

Machine shop called and said that the intake valve on number seven cylinder was also bent. 5 exhaust and 7 intake are side by side. Still perplexed on what happened. Anyone have any ideas.

[txab]

Valve springs maybe

[Doug_Scott]

Machine shop called and said that the intake valve on number seven cylinder was also bent. 5 exhaust and 7 intake are side by side. Still perplexed on what happened. Anyone have any ideas.

 

Did you take a look at all the possible head gasket leak points around cylinder 5 and 7? Is it possible that somehow coolant got into both cylinders via a blown head gasket? Something affected those two valves. It pretty much has to be the same thing, if it is hard to understand how two light bulbs with identical usage can blow at the same time, how hard to understand two unique occurrences happening at the same time, with identical results, in the same confined area? There are not many ways to bend only two valves, one in each of two side by side cylinders, and valves.

 

The valves either hung open, and where closed by the pistons, or, some foreign material went through engine cylinders 5 and 7, or they both got shocked by a sudden temperature change, like being sprayed by engine coolant, once exhaust valve is opened, up until intake closes. I am not really a fan of the coolant reasoning, it has always sounded like a scientific reason, and usually they give those reasons when they cannot really explain it in a way normal people can understand and relate to.

[ryan_jdsales]

Root cause is stuck lifters. So now the million dollar question is: How does a person remove these lifters. I can only get them to come up about a 1/2" by wiggling. Pulled the other lifters and they slip right out. Seems as if they are galled at some point.

[ryan_jdsales]

Was able to remove 1 of the lifters. Took about an hr and 20 minutes to get this one out. Worked for about an hr and a half on the other lifter and still don't have out. Anyone have to do this before? After removing the first one, slid good lifter in bore and it moved freely in bore.

[ryan_jdsales]

[Jsdirt]

I've never heard of, or seen that happen before in my life!

 

Why am I not surprised I'm seeing it in '16 on a low mile engine ...

[ryan_jdsales]

I've never heard of, or seen that happen before in my life!

 

Why am I not surprised I'm seeing it in '16 on a low mile engine ...

Don't u know the rules of a service department: (Service Manager training 101)

 

1. Never say I've never seen it before

2. Never say that it happens all the time

3. Always say we see it once in a while