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opinions on the root cause of this exhaust valve failure
Can anyone offer an opinion on the root cause of this exhaust valve failure. In particular, the white residue that accumulated on the failed valve. It is cylinder 6 of a Honda J35A7 engine in a 2010 Odyssey Ex-L. The engine has 256k km (160k mile). I've owned the vehicle since new. It has been maintanined per the maintenance schedule. No late oil changes, and no significant oil consumption problems. No serious problems until recently when it developped a persistent misfire on cylinder six. It had an S-VCM brand VCM disabler installed 26 months ago at 218k km (136k miles). I don't think that is related to the S-VCM since, but I'm open to opinions. All other cylinders pass a leak down test perfectly. Was it a just random failure? Is the white substance indicative of a root cause other than the valve itself? I'm asking in order figure out next steps, beyond obviously repairing the valve(s) or replacing the entire head.
Re: opinions on the root cause of this exhaust valve failure
Sunken exhaust valve seats are unfortunately kind of a common bug in Honda engines. Staying on top of valve adjustments can help to mitigate the chance of burning a valve, but it's just kind of a lottery as to which engines it will hit.
Re: opinions on the root cause of this exhaust valve failure
Originally Posted by snowblower
Can anyone offer an opinion on the root cause of this exhaust valve failure. In particular, the white residue that accumulated on the failed valve. It is cylinder 6 of a Honda J35A7 engine in a 2010 Odyssey Ex-L. The engine has 256k km (160k mile). I've owned the vehicle since new. It has been maintanined per the maintenance schedule. No late oil changes, and no significant oil consumption problems. No serious problems until recently when it developped a persistent misfire on cylinder six. It had an S-VCM brand VCM disabler installed 26 months ago at 218k km (136k miles). I don't think that is related to the S-VCM since, but I'm open to opinions. All other cylinders pass a leak down test perfectly. Was it a just random failure? Is the white substance indicative of a root cause other than the valve itself? I'm asking in order figure out next steps, beyond obviously repairing the valve(s) or replacing the entire head.
Re: opinions on the root cause of this exhaust valve failure
Originally Posted by Bibby 3340
looks to be coolant leakage.
No.
Since the exhaust valve burned it is more likely that it was not maintaining proper contact with the seat.
The white deposits are most likely ash from fuel deposits encountering high heat and burning/ashing on the valve(s).
When there isnt proper valve lash(too tight) the valve does not properly seat on the head. This is the way the exhaust valves cool/transfer heat.
Intake valves can last much longer as the intake charge is much cooler and of course the fuel also absorbs any heat as well as lubricates the seat.
Exhaust valve seats errode away, there is no cool intake charge or fuel to absorb heat and lubricate the seat.
These need to be checked for adjustment more frequently.
IIRC Honda recommends 90K mile valve adjustment. That may be fine for intake, but exhaust should be checked every 30k miles.
opinions on the root cause of this exhaust valve failure
