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Hello, noticed I had some oil coming from a spark plug hole. I noticed the spark plug wasn’t that tight so I tightened it up, but just for peace of mind, would the oil be from blowby through the spark plug hole? Running OMP and premix at the moment. (New motor break in)
Agree with FDAUTO, It may be just assembly lube from the new build. Clean it up and see if anything else shows up. Also noticed in the pictures that you got the plugs installed backwards - Per the Mazda OEM spec, the BUR7 plugs are supposed to go in the Leading (L) hole, and BUR9's go in the Trailing (T). You need to swap those - never run the hotter heat range plug in the trailing location.
what i think stands out more is the plug in the knock sensor hole. what is that about?
brand new motor you say.... wipe the oil off and see if it comes back. probably just some purging going on
it’s running off of a haltech, and I have single Bosch knock sensor on the front iron. There’s probably about 1-1.5 hrs of run time that caused that amount of oil.
Originally Posted by Pete_89T2
Agree with FDAUTO, It may be just assembly lube from the new build. Clean it up and see if anything else shows up. Also noticed in the pictures that you got the plugs installed backwards - Per the Mazda OEM spec, the BUR7 plugs are supposed to go in the Leading (L) hole, and BUR9's go in the Trailing (T). You need to swap those - never run the hotter heat range plug in the trailing location.
good catch on the plugs, I didnt even notice I had them swapped, thanks for pointing that out!
The plugs shouldn't be loose enough to allow anything to leak by like that, then you would be losing some compression. Hard to tell from the picture alone but it looks like the crush washers may not even be crushed thought which would indicate the plugs weren't tightened enough. I wouldn't just crank down on them though, I would check to see if they are tight first before giving it another Ugga Dugga. I'm leaning towards oil that was left in those outer pockets if the plugs are tight.
Last edited by boostin13b; Apr 1, 2024 at 12:48 PM.
How much premix are you running? With the OMP .5 oz. is usually considered appropriate
0.75oz per builder recommendation during break in period, but 0.5oz will be what I run it at. I’ll take the plugs out and make sure they’re in the correct spots and tighten them appropriately. Just out of curiosity, what happens when you have them flipped? 7s in the trailing and 9s in the leading?
The plugs shouldn't be loose enough to allow anything to leak by like that, then you would be losing a ton of compression. Hard to tell from the picture alone but it looks like the crush washers may not even be crushed thought which would indicate the plugs weren't tightened enough. I wouldn't just crank down on them though, I would check to see if they are tight first before giving it another Ugga Dugga. I'm leaning towards oil that was left in those outer pockets if the plugs are tight.
It takes more than a tiny plug/block leak to affect compression. That's such a small amount of oil the leak is VERY minor.
it’s running off of a haltech, and I have single Bosch knock sensor on the front iron. There’s probably about 1-1.5 hrs of run time that caused that amount of oil.
i see... the plug is just weird because it serves no purpose at all. its just along for the ride lol its like people that cap the ports on the side of the LIM
0.75oz per builder recommendation during break in period, but 0.5oz will be what I run it at. I’ll take the plugs out and make sure they’re in the correct spots and tighten them appropriately. Just out of curiosity, what happens when you have them flipped? 7s in the trailing and 9s in the leading?
With the hotter heat range plug in the trailing position (BUR7's), it's more likely to cause engine knock/ping/detonation. You NEVER want that to happen in a rotary.
It takes more than a tiny plug/block leak to affect compression. That's such a small amount of oil the leak is VERY minor.
I would think it would be harder to push out oil than gas through the threads. Yes the car would run because the threads will still hold most of the compression but if the plugs are loose, that is still an issue. We saw this happening with the Triton engines with Ford back in the early 2000's, plugs were either backing out or blowing out the threads completely. Poor metal quality/machining IIRC. The ones that would come in and have loose plugs would be throwing rich bank codes due to the loss of air from that cylinder causing that one to run rich. Cars still ran and most customers didn't know anything was wrong aside from a check engine light and sometimes a little ticking noise.
Either way, in this case, oil shouldn't be making it past the plugs in my opinion.
I would think it would be harder to push out oil than gas through the threads. Yes the car would run because the threads will still hold most of the compression but if the plugs are loose, that is still an issue. We saw this happening with the Triton engines with Ford back in the early 2000's, plugs were either backing out or blowing out the threads completely. Poor metal quality/machining IIRC. The ones that would come in and have loose plugs would be throwing rich bank codes due to the loss of air from that cylinder causing that one to run rich. Cars still ran and most customers didn't know anything was wrong aside from a check engine light and sometimes a little ticking noise.
Either way, in this case, oil shouldn't be making it past the plugs in my opinion.
I basically agree, but such a tiny seepage would not be noticeable on compression or leakdown. A significant leak or very loose plug is another matter entirely.
Did you notice any oil on the threads? If not, the oil running down could have been just left over from the rebuild and ran down when it got hot. Typically when an engine is built, it is turned over by hand many times with the plugs out to confirm even compression sounds and this may blow oil and assembly lube out of the plug holes and sits in those holes there. If not cleaned up it would run down when engine reaches temp but it does look a bit dirty to be brand new oil and assembly lube.
Did you notice any oil on the threads? If not, the oil running down could have been just left over from the rebuild and ran down when it got hot. Typically when an engine is built, it is turned over by hand many times with the plugs out to confirm even compression sounds and this may blow oil and assembly lube out of the plug holes and sits in those holes there. If not cleaned up it would run down when engine reaches temp but it does look a bit dirty to be brand new oil and assembly lube.
yea there was oil on the threads. I took out all the plugs and made sure they were in the correct spot then tightened them all appropriately. Seemed to start better and run better lol no oil leaking after about a half hr of driving
The gas/oil mix would be under high pressure the moment before it ignites. Would it be pushed by the threads if the plugs are loose, and not ignite?
Even with loose plugs, it will hold enough compression to ignite, just not as well. It also throws your mixture off when you lose some of it through the threads, how much depends on how lose they are. Usually not much, but like I said above, it was enough to set rich codes in when I was working on Fords in the early 2000's.
Were they loose when you pulled them out? They shouldn't have been really tight but shouldn't have just backed out with an easy wrist turn either.
some were quite loose. As in I could back them out by hand with some effort. Not sure how it happened, maybe overlooked, a dumb mistake.
Originally Posted by Redbul
What does the builder say?
I haven’t brought it up to him yet. If it’s just a matter of user error then no harm no foul, but if it’s persistent even after the corrections, I will definitely see what he thinks on it.
some were quite loose. As in I could back them out by hand with some effort. Not sure how it happened, maybe overlooked, a dumb mistake.
Good to know. Always nice to have that "peace of mind" finding the culprit. Even better when it didn't damage anything. I've seen it happen quite a bit over the years. People either tighten plugs with a 1/2" breaker bar or they are so afraid to strip the threads so much they don't crush the washer and this happens.
What you're seeing is just combustion chamber leakage from loose spark plugs. I was changing plugs and discovered the same thing on my '94 some years ago. The engine seemed to run normally.
What you're seeing is just combustion chamber leakage from loose spark plugs. I was changing plugs and discovered the same thing on my '94 some years ago. The engine seemed to run normally.
I think you’re right. I tightened them up appropriately, and so far no issues. Seems to start better too lol
