2G 7bolt front balance shaft rear bearing oil flow

[Kryndon]

Okay so from the thread I posted the other day about the little 1/16 BSPT oil plug screw, it turns out someone screwed in a very long stud in the rear oil port hole of the front balance shaft. Unfortunately, the stud is not a 1/16 but a normal M8x1.5 (still threads but loosely, hence why I was leaking oil from there). Here's a picture of this monstrosity:

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So, I'm at a critical stage where doing the wrong thing could wreck my engine in a matter of minutes, so I want to double-triple check everything and run it through with you folks, hopefully getting a solid answer.

I have gone over the VFAQ on balance shafts, went through Jafro's oil system video, and also came upon this comment by Wiseman "Project_TSI": "
Heres a new idea about the front balance shaft bearing, that has been a few times now and works flawlessly. Due to the fact that some BS bearings have spun in the block, the hole is too big and instead of getting a larger bearing to try to drive in, I came up w/ this idea.
On the front of the block there is a few machine screws that protrude into the block. On first look, one would think that these serve no purpose, but its actually where the factory drilled hole in the block to drill into the oiling chamber so it can oil the Bal. shaft. I forgot the thread pitch, but the screw can be backed out. If you get a small tap, and run it deep into the oiling hole then it makes threads in the block, this is the hole in whitch your trying to stop oil from comming from. You match up the thread, and run a new, longer bolt in the block, into the hole, thus stopping the flow of oil, w/ no need for a new bearing. Put some pipe dope on the block side of the screw and use some gasket sealer too. Wam, no need for a block off bearing and NO loss of oil pres.
It works."

So it appears the previous owner has tried doing what Project_TSI is suggesting, threading in a long enough bolt through both holes at the rear bearing to block off the oil flow. Now, my front balance shaft is obviously removed and the rear bearing WAS NOT rotated to block off the flow.

My question is, does the second hole (the one further in) lead to any other high pressure oil feeds, or does it in fact just drain down to the oil pan as seen in this schematic (by Jafro), I've marked the front bearing oil flow with the red lines?

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IF the second hole only leads to the oil pan and nowhere else, can I just order the OEM 1/16 BSPT plug screw and put it in the place of the long stud? Effectively blocking off the high pressure feed but leaving the second hole open as technically there will be nothing flowing through there? Or should I do as the Wiseman has said and make a proper sized stud that threads into both holes simultaneously?

I hope my questions make sense; I really would appreciate help right now as I'm currently in the process of rebuilding the turbo and would hate to wreck the engine because of this balance shaft nonsense!

 

[Kryndon]

Okay so I put the turbo back on the car and decided to remove the long stud and thread in a shorter bolt with a washer and a rubber o-ring. I figured the inner hole is simply a direct return to the oil sump as shown in the diagram.

The only other things I have actually changed on the car today were a new thermostat, a few new silicone water hoses and a new oil filter. I put ~3.5 qts of 10w-40 as usual and made sure to top it up; the dipstick reads at the middle. However, after letting the car idle initially, I noticed that the oil gauge was reading at the lowest mark (right at the L). I revved it up a bit but it barely went higher. I opened the oil cap to check if the lifters are squirting oil and they were, there was a constant stream. I took it on a 120 mile journey and realized it was not running with the correct oil pressure at all. Here is a picture of the gauge showing pressure at idle and the yellow line is at cruising RPM (2300).

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Also the engine seemed to be way hotter than usual, and I could hear liquid boiling sounds around the turbo area. However the water temp gauge was constatly at the middle (data logger shows 195F throughout). The only thing that would make sense to me is if in fact the second oil channel opposite of the front is the high pressure oil feed for the front balance shaft, and because I left it unblocked, it must now be squirting lots of pressurised oil, starving the rest of the engine. Here's a simple picture I made in Paint to illustrate which holes I'm taking about:

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What do you guys think? Could this be the issue? I also measured the total depth of the drilled hole from the front of the balance shaft housing to the bottom of where that (???) hole is, and it measures 3.4 inches deep.

 

[19Eclipse90]

The inner port is the feed, is high pressure, and needs to be blocked or you'll experience issues as you've described. I'll come back to clarify later.

Edit: This thread describes the oil pathway through the engine and is worth a read: OFHs Oil Flow Pathways For The Engine (Questions)

Before getting too carried away, here's a couple other threads that may have something useful in them for you:
BSE- HELP!! is this common or not?
Blocking off oil galley

At this point you cannot use the 1/16 BSPT plug as its nominal diameter is smaller than the nominal diameter of an M8 bolt. You will have to use something larger to plug the hole.

The only thing that would make sense to me is if in fact the second oil channel opposite of the front is the high pressure oil feed for the front balance shaft, and because I left it unblocked, it must now be squirting lots of pressurised oil, starving the rest of the engine.

This is the way it works; probably why it is the only thing that makes sense to you at this point. The inner port you did not block is the feed for the bearing. The oil returns to the pan by "spilling" out the sides of the bearing's bore so what Jafro has diagrammed is still correct. That feed port is the same feed for the main bearings and the same port that transfers oil to the head.

Here's a picture of the front BS bearing bore with a clean way of blocking the port, but the same can be done for the front shaft's rear bore. It is the missing picture in at least one of the above links, ultimately from EvoM site.

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[Kryndon]

The inner port is the feed, is high pressure, and needs to be blocked or you'll experience issues as you've described. I'll come back to clarify later.

​

You're an absolute godsend. Thank you very much for all this information!! I cannot believe I did not come across it (should have done more research before putting everything back together). I did have a gut feeling of what that long stud was doing but I was not fully aware on which side the main oil gallery was. Of course it would be on the inside, it makes sense!

Unfortunately like I said I already did about 120 miles on the car yesterday but I did not exceed 55 mph. At one point I stopped to check everything and I could hear number 1 or 2 rod knocking a little bit, but it went away. I may have already done the damage. But this engine had a bottom end rebuild less than 5000 miles ago (same exact issue, no oil pressure and loose rod ends), but I was not completely aware of all these systems and how they work. This engine isn't going to take another rebuild and I cannot find a spare block anywhere here.

To make things worse, I am also unable to remove the engine and open it up to do everything cleanly. So my only option would be to machine a single long stud with two different diameters, a 1/16 or similar on the far end, and a 1/8 at the other, so I can thread it simultaneously in both holes.

 

[19Eclipse90]

I would expect it to be a bit difficult to time the threads for the outer hole to the inner hole with a single screw or stud. The outer threads will continue driving the screw or stud forward regardless of where the threads for the inner threads begin.

Have you considered simply machining the tip of the plug to act more along the lines of an interference/press fit to seal off in the bearing feed? Similar to the stud you pulled out of there but slightly more refined, it was suggested in one of the threads I linked before.

 

[Kryndon]

I would expect it to be a bit difficult to time the threads for the outer hole to the inner hole with a single screw or stud. The outer threads will continue driving the screw or stud forward regardless of where the threads for the inner threads begin.

Have you considered simply machining the tip of the plug to act more along the lines of an interference/press fit to seal off in the bearing feed? Similar to the stud you pulled out of there but slightly more refined, it was suggested in one of the threads I linked before.

Yes I did saw that idea mentioned and now that you raise a good point, I may have to rethink it. The only thing I'm worried about with the tapered end pressing against the smaller hole inside is how good of a seal it will make. Unless I apply a lot of red high strength thread sealant on the tip or possibly RTV? I may machine two pieces and test fit them to see which one would work better. I checked and saw that the NPT and Metric threads use 60 degree flank angle, which explains why the M8 stud was threaded in fairly easily.

I will see how I get on with this and of course report back. Best case; I'll get my oil pressure back and it wont spin bearings in the near future (got a 2300 mile journey next month).

 

[19Eclipse90]

A tapered or full-round tip on the end of the shaft ought to plug the inner hole when combined with the threads of the outer hole, to get a decent block-off. Sure it may not be 100%, but I imagine it would be close.

To the same point, I would rely solely on the machined shaft and the block to create the seal on the inside. If anything, use what you need to seal the outer hole. If there is concern that the shaft might back out, maybe throw a little tack weld on the head to prevent it from turning out.

Do let us know what you come with!

 

[Kryndon]

So, after a long battle with that ridiculous oil feed screw to the turbo, we managed to fix the issue! Well, technically it's like before but at least this time the stud has a head on it so it can be removed later on. It's a very simple 62mm long steel shaft, which I machined down to 7.8mm and tapped with an M8 1x25 thread and rounded off the tip. This way, the bolt can thread into the 1/8 NPT hole (which is 7.9mm in diameter and the same 60 degree flank angle) and go all the way up to the oil feed. I am not quite sure how snuggly it blocks it, as I had to add two washers to the bolt and also glued them with a bit of RTV (sorry Bobby it was my only sealant at the time!). It doesn't seem to be leaking now, and I definitely got my oil pressure back. The car runs and pulls hard, boosts fine.

However, I am beginning to think that I may still be having less oil pressure than I should. I know that my rear balance shaft is still in place, but I saw that the front balance shaft's first bearing actually had that little OEM grub screw plug on the outside. I am beginning to think it may still be leaking oil from that initial oil feed like the one in the pictures above. I will put up a picture of where my needle sits at each stage and maybe see if other people with a front BS delete have the same pressure. But yeah overall I'm glad this was fixed before I ruined the engine. Thanks a lot for the help!!!

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