Oil on spark plug threads? (1 Viewer)

[AZBoatHauler]

Like the title indicates - I found oil coating the threads on the spark plug in cylinder 7.

I did find a thread on here saying that is known issue and seemed to indicate changing seals may not remedy the issue - what says the wisdom of the forum? Anyone else encounter this?

Rig is a 2017 with 103k miles. No codes, no driving symptoms.

 

[bloc]

Drive on.

The "issue" is when the spark plug tube starts to fill with oil. In that case changing the gaskets at the top often doesn't resolve it, the problem is where the tube is pressed into the head. See some of @Taco2Cruiser writing on the subject for more details.

I'd bet most of us have some oil on the threads and it doesn't cause an issue at all.

 

[Fisher23]

Looks normal.

 

[AZBoatHauler]

Looks normal.

definitely not normal.

 

[Zill]

This can happen due to a failed tube seal around the spark plug, but the risk of messing something else up to do the fix is not worth it (this is not an easy repair by any stretch of the imagination and most shops will not do a good job to fix it). Put a new spark plug in and drive on. The inherent mating of the threads to the head with the spark plug will make sure no oil gets into the combustion chamber when the plug is in.

My only concern would be hydro locking the engine if too much oil got into the combustion chamber when you took out the spark plug. After you install the new plug, let the engine sit overnight so the oil can seep past the rings and clear out of the combustion chamber.

 

[bloc]

For a high mileage engine, yes, normal. Not always present, but nothing to worry about. I’ve had it on a few cylinders at both of my spark plug changes.. at 105k and 195k.. with absolutely zero hint anything is unhealthy about my engine. And this was with no hint of oil in the tube itself either.

Some engines just tend to push oil or combustion byproducts up the threads.. this is not unique to Toyota by the way.

My only concern would be hydro locking the engine if too much oil got into the combustion chamber when you took out the spark plug.

There would need to be enough oil to submerge the hex and part of the insulator to come close to hydrolocking that cylinder. Not just on the threads.

 

[Zill]

For a high mileage engine, yes, normal. Not always present, but nothing to worry about. I’ve had it on a few cylinders at both of my spark plug changes.. at 105k and 195k.. with absolutely zero hint anything is unhealthy about my engine. And this was with no hint of oil in the tube itself either.

Some engines just tend to push oil or combustion byproducts up the threads.. this is not unique to Toyota by the way.



There would need to be enough oil to submerge the hex and part of the insulator to come close to hydrolocking that cylinder. Not just on the threads.

Depending on how bad the leak is, there could be a good amount of oil sitting on top of the threads (pooling up on top of the plug), and when you unthread the plug, you could get a good amount of oil to drop down in the cylinder.

I am probably being a bit conservative with that assumption, but hydro locking a 20k+ engine would not be fun.

 

[AZBoatHauler]

Engine runs just as smooth or better than before I changed plugs so thankfully I didn’t manage to make it a paperweight this time. Appreciate the input. Found an old thread on here saying it is more common in the back cylinders which is what I had/have…

 

[bloc]

Depending on how bad the leak is, there could be a good amount of oil sitting on top of the threads (pooling up on top of the plug), and when you unthread the plug, you could get a good amount of oil to drop down in the cylinder.

I am probably being a bit conservative with that assumption, but hydro locking a 20k+ engine would not be fun.

Understood, I’m saying we’d see evidence of oil on top of the gasket as well, like on the hex and ceramic, but that doesn’t seem to be there in this case.

Some with oil inside the tube definitely are in danger of that.. but for anyone paying attention as they pull the coil and go to stick a socket in there.. it should be somewhat obvious the oil needs to get removed first.

 

[Fisher23]

When I first saw one like that it made me wonder if the threads in the head were all taped to exactly the same tolerances.

 

[onelittlestar]

Understood, I’m saying we’d see evidence of oil on top of the gasket as well, like on the hex and ceramic, but that doesn’t seem to be there in this case.

Some with oil inside the tube definitely are in danger of that.. but for anyone paying attention as they pull the coil and go to stick a socket in there.. it should be somewhat obvious the oil needs to get removed first.

I pulled a few messy ones recently, but enough to hydrolock it? I feel like that would be very obvious, like pouring out of the tube obvious.

 

[Roc14]

200k miles on the LX found oil in 3 out of 8 spark plug wells. How hard is it to replace gasket and spark plug tube gaskets? Compared to valley plate leak job? I was able to do the valley plate leak and that was a pain.

 

[bloc]

200k miles on the LX found oil in 3 out of 8 spark plug wells. How hard is it to replace gasket and spark plug tube gaskets? Compared to valley plate leak job? I was able to do the valley plate leak and that was a pain.

The tube and cover gaskets aren’t difficult but likely wasted work, as they aren’t the root cause. Per an expert on working on these vehicles (@Taco2Cruiser ) the issue is where the tube is pressed into the head, and pulling the tubes to address that seal is much, much more difficult.

 

[Roc14]

The tube and cover gaskets aren’t difficult but likely wasted work, as they aren’t the root cause. Per an expert on working on these vehicles (@Taco2Cruiser ) the issue is where the tube is pressed into the head, and pulling the tubes to address that seal is much, much more difficult.

I did read that thread at this point just going to take it in to Toyota and let them take a look and see what it needs. Thanks

 

[bloc]

I did read that thread at this point just going to take it in to Toyota and let them take a look and see what it needs. Thanks

Good chance they’ll want to remove the heads. Don’t let them.. it’s worth investigating methods to have a resourceful mechanic pull and seal the base of the tubes.

Alternately you can just run it.. you can buy a whole lot of coils for the price of fixing this. Just find an appropriate interval to pull the offending coils, clean the oil, and if needed replace the coil. It’ll probably be in the tens of thousands of miles range.

 

[Roc14]

Good chance they’ll want to remove the heads. Don’t let them.. it’s worth investigating methods to have a resourceful mechanic pull and seal the base of the tubes.

Alternately you can just run it.. you can buy a whole lot of coils for the price of fixing this. Just find an appropriate interval to pull the offending coils, clean the oil, and if needed replace the coil. It’ll probably be in the tens of thousands of miles range.

Got it thanks for the tip. I'm going to pull them and take a look at the coils now it's been about a month since spark plugs were swapped out.

 

[grinchy]

Had on mine #6 if I recall. probably on original plugs still when swapped around 240k miles.

 

[Roc14]

Good chance they’ll want to remove the heads. Don’t let them.. it’s worth investigating methods to have a resourceful mechanic pull and seal the base of the tubes.

Alternately you can just run it.. you can buy a whole lot of coils for the price of fixing this. Just find an appropriate interval to pull the offending coils, clean the oil, and if needed replace the coil. It’ll probably be in the tens of thousands of miles range.

Pulled the 2 coils that had oil when I swapped out the plugs. They had less oil this time around when I pulled them there's very little oil down by the plug. Blew what I could out of the coil. It's leading me to believe the spark plug tubes' gaskets probably have a cracked when I pulled the plugs out. I didnt blow them out when I swapped the plugs. They have never been changed 12 yrs 200k miles they have to be hard by now. I'm not burning or losing oil. I measured the last oil change and pulled out almost 8 quarts. It runs smooth and quiet when on the road don't even know the engine is running at times. Definitely won't have them pull the heads.

 

[onelittlestar]

Pulled the 2 coils that had oil when I swapped out the plugs. They had less oil this time around when I pulled them there's very little oil down by the plug. Blew what I could out of the coil. It's leading me to believe the spark plug tubes' gaskets probably have a cracked when I pulled the plugs out. I didnt blow them out when I swapped the plugs. They have never been changed 12 yrs 200k miles they have to be hard by now. I'm not burning or losing oil. I measured the last oil change and pulled out almost 8 quarts. It runs smooth and quiet when on the road don't even know the engine is running at times. Definitely won't have them pull the heads.

I'm going to do the same this weekend, luckily the middle plugs were the offenders, so easy to check.

 

[Roc14]

I'm going to do the same this weekend, luckily the middle plugs were the offenders, so easy to check.

Good deal yeah mine were towards the front and not the back makes it a lot easier to pull and inspect.