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Discussion Starter #1
Hey folks,

I've got a peculiar issue: in the process of rebuilding my 5M, I've noticed that there's a hole near the power steering bracket that communicates with the exhaust camshaft housing and possibly the nearby oil pressure regulator. Please let me know if the link to the google pictures below don't work for anyone. I've included unlabeled and labeled pics to help.


Can anyone identify this? It's not threaded and approximately the size of an M12-M14 bolt hole.
Unfortunately, I don't have any pre-machine shop pictures to determine if it's something the shop did. All the images of exhaust side 5m heads I could find online have it plugged.

Short of taking the head back to a shop/welder, any ideas on a fix?
Does this hole see high oil pressure or is it just part of the down draining system?
JB weld? Find an appropriate sized plug + RTV silicone?

Thanks in advance
 

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Tap it out and put a threaded plug in it. I'd take it back to the place that did the work and have them fix it.
 

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Are you sure the hole goes into the oil system??

There is a engine lifting hook bolted to the front of the engine somewhere near the front of the exhaust manifold..
 

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On second look in the manual the bolt for the engine hook may only bolt to the power steering bracket?
 

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Discussion Starter #5
AJ, yeah the engine hook is directly on the power steering bracket, not direct to the head (unlike the rear lifting hook).

I've done a bit more digging. I was mistaken about the pathway. It looks like this hole forms a T with the oil pressure regulator and the drain to sump but I can't be certain (see images).

Coming from the regulator side, does it travel straight down through the same oil chamber that the rear upper timing cover seals via the Tennessee gasket? Then down to the sump through the engine block. I believe this is the same chamber that both camshaft housings drain through.

Hopefully the images orient where the passage travels through in relation to the timing covers and block.


Approximate trajectory of the passage:


If someone has a better picture of this chamber and the passages it collects, please post it! I really wish I took more pics and studied the passages. Pics below were from various sources and used to help deduce oil flow:


I guess the heart of my question is to determine whether or not this mysterious hole sees high or low oil pressure.
 

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John, Great detective work Sir!! I'm not sure at this point, have to review the TSRM further...
 

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Doesn't matter about high/low, its an oil passage, and it needs to be plugged. Here is that hole unaltered on my motor...
14106


So these holes are necessary for manufacturing. The main oil galley in the plug has a plug like this too, behind the water pump. The factory drills out the galleys, then presses these plugs in. If you get your block or head hot tanked, the machine shop will drill these out. They have stainless steel allen bolt plugs in all sizes to go back in after, but yes you have to tap the holes. You want to find the best oil safe high temp RTV you can find for these! I have had a chronic oil leak on my motor since shortly after its rebuild because I used Permatex high temp thread sealer on my plug threads. That stuff claims to be oil resistant, but it doesn't hold up. I found some grey Aisin high temp oil proof RTV at my local parts store amazingly enough, I will try that next.
 

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Discussion Starter #8
Thanks, Suprafiend. The reason I wanted to know if it was high/low pressure is because it determined my method of plugging. If it was low pressure, I would have Black RTV silicone'd it and capped it with some sort of flange bolt...probably still left it untapped. If it leaked, then I would have stepped up the method of sealing. The location isn't too terrible for me to work on in the engine bay.

I learned that it actually is seeing high oil pressure because it's continuous with the oil gallies(galleries?). I ultimately ended up using high temp JB weld putty stick, roughened up the bore and the "seat" area then ground a bit to be more flush.

I wanted to tap it so I could have the possibility of monitoring oil pressure closer to regulator (for my own data curiosity) but I'm not confident in my ability to perfectly drill straight for an M12 tap...nor did I really want to remove an already installed head. I'll keep it to myself if I end up regretting this decision lol. I think the bore was measured ~9.5mm and it was just tad large for an M10 tap and too small for an M12 tap.


Showing it's continuous. Removed the oil galley plugs near the water pump. Shined a light from the oil pressure regulator. Visible light in both the mysterious hole and the oil galley plugs. So I at least learned 2 things. Which hole the oil pump pressurizes and that I need to close the mysterious hole in a method that handles 70 psi on 5W-30 oil. Maybe more if I try out diesel Shell's diesel 15W-40 oil.


I took more pics of the head and block to understand the flow. I'll try to get them up soon and hopefully folks can chime in.
 

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I'm not sure I would want to trust a clump of jb weld to that task to be honest. A plug isn't going anywhere, you just need to make it seal at least.
 
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