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A burnt valve. I haven't read much of those occurring yet I'm sure they do. Poor metallurgy/hardening is all I can think would cause it, it is nothing user oriented that caused that. Just bad luck.

Will you have it repaired?
 

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Any idea what may have caused this? Low mile car, purchased it when it had 30k miles, View attachment 251280
and its out of warranty. Any ideas of how to avoid it happening again? Common issue?
Any codes, check engine light (CEL)? It's was likely a manufacturing defect; perhaps inadequate clearance between the exhaust cam lobe and the bucket follower over the valve spring. This would keep the valve from fully seating in the head when closed, preventing it from transferring its heat to the cylinder head. The valve then overheats and fails. Although this isn't much comfort, at least the valve head didn't break off and destroy the piston. Additionally, carbon deposit formation in the valve guide may have caused the valve to stick open slightly with the same end result. You would have noticed a skip in engine and the computer would have detected excessive misfires, setting off the CEL. However with the low mileage I'd go with the former and this usually happens to the intake valve. Another factory defect could be that the valve seat might not have been sufficiently hardened, causing valve seat and valve face wear resulting in exhaust gas leakage. The only real way to know is to measure the valve clearances before disassembling the head.
I also want to mention that fuel detonation (pinging, knocking,) can damage exhaust valves from overadvanced ignition timing or excessively lean air fuel mixtures. Too much boost without sufficient fuel enrichment in a turbo car can also do this. Any of these would likely provoke the CEL to come on. This is not an exhaustive list by any means but it may lead you to find out what happened. If I were in your situation I'd want to know too.
 

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Discussion Starter · #4 ·
A burnt valve. I haven't read much of those occurring yet I'm sure they do. Poor metallurgy/hardening is all I can think would cause it, it is nothing user oriented that caused that. Just bad luck.

Will you have it repaired?
I couldn't find any burnt valve issues either. I plan on fixing it, the head is on its way to the machine shop to see if they can put a new valve seat in it that was damaged also. I can take a bad luck situation, but I don't want to have to worry about it happening again. Seams like this model has been around long enough now that if it were a common issue there would be more flags on the net. Thanks for your response.
JP
 

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Discussion Starter · #5 ·
Any codes, check engine light (CEL)? It's was likely a manufacturing defect; perhaps inadequate clearance between the exhaust cam lobe and the bucket follower over the valve spring. This would keep the valve from fully seating in the head when closed, preventing it from transferring its heat to the cylinder head. The valve then overheats and fails. Although this isn't much comfort, at least the valve head didn't break off and destroy the piston. Additionally, carbon deposit formation in the valve guide may have caused the valve to stick open slightly with the same end result. You would have noticed a skip in engine and the computer would have detected excessive misfires, setting off the CEL. However with the low mileage I'd go with the former and this usually happens to the intake valve. Another factory defect could be that the valve seat might not have been sufficiently hardened, causing valve seat and valve face wear resulting in exhaust gas leakage. The only real way to know is to measure the valve clearances before disassembling the head.
I also want to mention that fuel detonation (pinging, knocking,) can damage exhaust valves from overadvanced ignition timing or excessively lean air fuel mixtures. Too much boost without sufficient fuel enrichment in a turbo car can also do this. Any of these would likely provoke the CEL to come on. This is not an exhaustive list by any means but it may lead you to find out what happened. If I were in your situation I'd want to know too.
Thanks for all the info Robert, good stuff. There were no codes, and engine ran smooth as silk prior to the the cylinder dropping all at once. We were running highway speeds on our way to the airport and I got a light vibration ant slight loss of power. I new we had an issue when we got off the highway and rolled off the RPM's and it got rough but still running. I thought I lost a coil pack. Drove it home and took it to my buddy's shop. On my way home with it is when the Check engine light came on, I would have thought it would have came on right away. This is my first Turbo cay that I've owned so I'm learning as I go.
Thanks again for the info.
JP
 

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Thanks for all the info Robert, good stuff. There were no codes, and engine ran smooth as silk prior to the the cylinder dropping all at once. We were running highway speeds on our way to the airport and I got a light vibration ant slight loss of power. I new we had an issue when we got off the highway and rolled off the RPM's and it got rough but still running. I thought I lost a coil pack. Drove it home and took it to my buddy's shop. On my way home with it is when the Check engine light came on, I would have thought it would have came on right away. This is my first Turbo cay that I've owned so I'm learning as I go.
Thanks again for the info.
JP
 

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First turbo for me, too. Also a learning experience, especially the electronics. I am definitely going to buy an XTool D8 scan tool. I was an ASE certified mechanic running a garage in the 1980s and most of what was pertinent to auto repair then applies to cars today. In those days a jumper wire was all one needed to see trouble codes. I wonder if it is worth it to replace all the exhaust valves. Certainly if there is valve seat recession and significant face wear on more than that one burnt valve. Check the cost of what the machine shop wants for the job vs. a remanufactured head. Also check the dimensions of the exhaust cam and that the variable valve timing mechanism is functioning properly.
 
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