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Discussion Starter · #1 ·
Not quite a murder mystery but one for you detectives out there to ponder.

Long Story Short
325 auto to 330 manual conversion, full donor engine rebuild, block and head machined, standard head gasket, new gaskets throughout, all Elring brand, new flywheel bolts with sealant pre-applied, new rear main seal with high-temp sealant on the bigger two bolts and the rear gallery plug, seated all the way in (learning from 50sKid's oil leak saga).
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Process
Engine reinstalled, everything hooked up under the hood, coding done. Removed main relay and fuel pump fuse to prime the engine and build up oil pressure, cranked for about 15 seconds. Reinstalled relay and fuse.

First start - purely to check if she'll fire up, ran for about 10 seconds.

Second start - reinstalled the exhaust, ran for 1.5 to 2 minutes to bleed the power steering and check the gearbox was engaging. Also finished bleeding the cooling system. At this point there may have been some air pockets left still, mistakenly thought the engine needed to be running to bleed it fully. Finished hooking everything up, dropped the car down, torqued wheel nuts - ready for its first drive.

Third start - did a quick run around the block, all of 3km. Engine felt great, lifter tick as to be expected, maximum 2.5k RPM, got up to temperature. Returned to driveway only to find a trail of oil all along the road and a steady drip from between engine and gearbox as can be seen at the end of the video.

That's about as far as I got with it. Ideally at that point I needed to go for a longer drive to start bedding in the piston rings but did not feel secure enough to do that with the magnitude of the leak.

Investigation
Initially suspected I must have messed up when installing the rear main seal. Dropped the gearbox to find the seal bone dry. Now struggling to pin down what could be causing such a significant leak. Engine is fully cleaned and the oil is still new and virtually transparent, which doesn't help in trying to diagnose the culprit.
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Oil seems to be running down the intake side of the engine, along the left side oil pan bolt and into the bell housing. No signs of leaks on the exhaust side.
Inspecting the backing plate, there is a wet patch right above the starter area (the most puzzling one) and one below it.
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Main Suspect - Crank Position Sensor
The only obvious leak looks to be the crank position sensor. There is a puddle right under it (the engine had been tilted back and forth and I have been feeling around that area which is why the puddle doesn't appear as big anymore in the photos) so it is possible the oil is pooling up there, running down along the backing plate, onto the oil pan bolt and into the bell housing, although I have serious doubts whether this alone would cause a strong enough leak to be producing such a steady stream. Also suspect it would have made a much bigger mess along the side of the engine if that were the main source.
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The sensor is a brand new VDO (OE) unit with a new O-ring. Looking at it, the design is not great and I feel it would benefit from being held with two bolts, one either side of the opening instead of the one but it is what it is.
Looking at the old engine block, the whole area is severely caked with oil so it does look like it is a very common failure point. Question is - how do I make it seal better? Another new O-ring with RTV sealant applied for good measure?
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Again though, I doubt that this alone would produce such a steady stream of oil on its own. And even though it does look like it was quite a severe source of a leak on the old engine as well, it never left any marks on the driveway so it couldn't have been that significant, whereas here it left a whole pool in a matter of minutes. Whilst it is a definite leak, I doubt it is the only one.

Other Suspects
Wondering if it could be the oil pan gasket as well in that one corner? I did install it with the engine up on a stand, all evenly seated, sealant applied on the join between the block and the rear main seal housing, all bolts torqued to 10Nm. One thing I'm wondering about is whether the longer bolts had a different torque spec? The manual only specified by grade and all 4 longer ones were still 8.8 grade bolts, just like all the shorter ones. Weird that a new gasket would start leaking straight away regardless.

Only other minor concern is the gallery plug. I did take it out and cleaned it thoroughly of the remnants of the old sealant and applied white high-temp sealant, then seated it all the way in. I find it odd that originally, the plug sat almost flush with the surface of the block and thus would not have been threaded all the way in from factory so not sure if driving all the way to the end is the right thing to do? Then again, leaving it half way in and hoping the sealant to do all the work is a bit sketchy too. The area around it was slightly damp to the touch but again, I doubt that this alone would cause such a significant leak.
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Mystery Leak
The biggest question remains the botch of oil on the backing plate above the starter. Cannot figure out what might have caused that. Looking and feeling around the engine, there doesn't look to be an obvious cause for it. There is no signs of leaks along the side of the engine further up from the crank sensor, nor does it look to be coming from the valve cover or between the block and head. The gallery plug also sits below that spot so really struggling to figure that out.
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Other Considerations
I really wasn't happy with the job the machine shop did. Other grievances aside, in the specific area of the leak, they left a few scuffs and chipped edges. As a remedy, I used a fine file to get rid of the high spots and made sure to apply a decent amount of sealant in the area. Whether that was enough or not, I cannot be 100% sure. The gasket also sits inside where the biggest chips were so should have sealed before getting that far. I also used 400-grit sandpaper to get rid of the remnants of the old gasket.
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The oil pan that came with the donor engine also looks a bit scuffed up along the bottom so the previous owner must have bottomed out on something somewhere along the line. Pretty weird as the car did have the aluminium reinforcement plate installed when I got it so no idea how it could have picked up this sort of damage.
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Best Course of Action?
Really struggling to settle on the best course of action. The maximalist approach would be to get the engine out again, clean up the pan from the old engine and seat that on with a new oil pan gasket, new rear main seal housing with the seal pre-installed, new gallery plug with sealant pre-applied, new O-ring on the crank position sensor with a dab of RTV, new flywheel bolts with sealant pre-applied and go again. Basically throwing a bunch more money and effort at it.

Any thoughts and suggestions very much appreciated. I know it's quite a long post with probably more information than necessary but really thought I'd lay it all out there as I'm starting to veer into sheer desperation with this thing. After putting more than a year's worth of weekends and vacation time into this project, I was really hoping to have the car up and running again and this oil leak came as a real kick in the balls. Just want to make sure I get it right before putting everything back together. Not sure what mental state I'd find myself in if the issue were to persist and I'd have to tear it apart once again.

Thanks team
 

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Sorry to hear... Looks like a pretty thorough and expensive rebuild - time, effort and money... I can fully appreciate how deflating an oil leak like this is after such a rebuild.

I can't see the video but the description of a steady drip to me indicates that the leak is coming from somewhere under pressure. Unless there is a crack in head or or block near a pressurized gallery, this would rule out just about everything except the gallery plug.. The gallery plug is also exactly at the point on the metal shim. above the starter. But the plug, based on photos and your description, looks like it is installed correctly.

I would pour a bottle of oil-compatible UV dye into the oil fill and run it again with transmission off to identify your leak. Then use UV glasses and a flashlight to see it.

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Another area there is the rear main seal housing gasket. I remember when I ordered mine it came folded and being metal it was useless afterwards. Also what about a leak from the valve cover itself from the side facing the injectors? Like a hairline crack.
 

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Agree with Effduration - get the dye kit as it will lead you directly to the leak. I've recommended this countless times here on the forum and others over the years, and have yet to have anyone actually DO it. It seems like people have the odd perspective that this is a gimmick of some sort, when the reality is it is about the most dramatically effective way to find a leak. Best.
 

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Discussion Starter · #6 ·
I would pour a bottle of oil-compatible UV dye into the oil fill and run it again with transmission off to identify your leak. Then use UV glasses and a flashlight to see it.
I wouldn't have thought about using dye but a mate of mine did suggest running the engine again to the try and see better. That idea fell apart after we remembered that with the transmission out, there's nothing holding the starter in place...
Is there a method of starting it without the starter? We couldn't think of one.

Another area there is the rear main seal housing gasket. I remember when I ordered mine it came folded and being metal it was useless afterwards. Also what about a leak from the valve cover itself from the side facing the injectors? Like a hairline crack.
The RMS gasket is a possibility but really does not appear obvious. It may be leaking seemlessly but it still wouldn't be the only leak as there are wet patches above that area. The valve cover looks to be dry all around from what I can see. Only place left to check is remove the metal plate at the back of the head that holds the O2 sensor wires in place and have a feel there but from peeking up at it, it all looks dry.

Did you put sealant on the bolts holding the RMS housing on?
The two big ones, yes.
 

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Mounting the starter without the transmission installed on an M54 is a challenge.

Does your old Auto transmission have a removable bell housing? Some do, Some don't
I actually have just a bell-housing for the M54 test stand I hope to build some day.

Otherwise, maybe somebody can fab up a chunk of metal using the thin metal shim piece between engine and trans as a template. I don't think the shim itself with a couple of sockets and bolts will be strong enough.
 

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Discussion Starter · #9 ·
Does your old Auto transmission have a removable bell housing? Some do, Some don't
I actually have just a bell-housing for the M54 test stand I hope to build some day.
Gave the old transmission away a few months ago unfortunately but absolutely good point. Will try to source one or check at the wreckers if they won't charge an awful lot.
Is the engine side of the bell housing the same on a 4-cylinder engine as well? Might make it easier to find.

Perhaps you could take the plugs out and spin the engine from the front via the crank dampener with an impact gun or such if oil movement is the goal ?
Don't think it'd get it going fast enough to generate the oil pressure.
 

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Gave the old transmission away a few months ago unfortunately but absolutely good point. Will try to source one or check at the wreckers if they won't charge an awful lot.
Is the engine side of the bell housing the same on a 4-cylinder engine as well? Might make it easier to find.


Don't think it'd get it going fast enough to generate the oil pressure.
Just a thought oh well.
 

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It’s hard to tell on my phone, but looking at this picture do I see it correctly? The left bolt is wet with oil and the right bolt is dry?

The sealant you used was a plumbers pipe dope sealant?

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Discussion Starter · #16 ·
Have to be mindful though of not letting the car idle for too long though. Having installed new piston rings, I really need to start putting some load on it and go for a longer drive ASAP. Don't have any experience breaking in new engines but... at what point would that start becoming an issue?
 

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Discussion Starter · #17 ·
I would pour a bottle of oil-compatible UV dye into the oil fill and run it again with transmission off to identify your leak. Then use UV glasses and a flashlight to see it.
Agree with Effduration - get the dye kit as it will lead you directly to the leak. I've recommended this countless times here on the forum and others over the years, and have yet to have anyone actually DO it. It seems like people have the odd perspective that this is a gimmick of some sort, when the reality is it is about the most dramatically effective way to find a leak. Best.
Really weird one this. I'm actually really keen to try this out but am really struggling to hunt some down. Could order some from overseas but really want to get this sorted ASAP and not have to wait weeks for it to arrive.
Absolutely no luck finding some locally. The only one I found from local suppliers is this 16oz bottle for NZ$630!!! What the absolute hell. Have also called around several auto supply stores, as well as engine reconditioners and machine shops and literally nobody has ever even heard of UV dye being used in engines. Just New Zealand things I guess. Utterly bizarre.
Guess I'll see if I can pinpoint it without the dye. Seemed like a severe enough leak that would hopefully be obvious anyway.
Thanks for the suggestion though, will look into it for the future.
 

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Yeah I think you should just run it with your slick Starter adapter....

If it drips again like it did before, you should be able to see the source...

I don't have a perfect answer on running the engine without a load...But I have re-ringed several M54's and I don't think you're going to cause any damage by running without the trans attached and/or under load...
 

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If you pull the plugs, spinning it on the starter should be OK.
The thing rotates a LOT in the first 2 minutes after starting, so 2 or 300 rpm
on the starter isn't going to match that.

My experience with a half- dozen or so break- ins has been that the key is to warm it up, jump in, and
hit it hard- not to redline, but heavy load, long overruns, and repeat 10 or so times.
Then you're golden- the rings have started to seat properly, and everything else is already OK-
exception being, if you have a new cam and lifters, don't let it idle below 1800 or so,
which isn't too hard.

4 laps on your average road course seems to be ideal, then a cooldown and check, and
off you go again.

I had a leak once, (I messed up the front main seal) and I hate to admit, but I ran it anyway,
and it lost less than a quart of oil. But made a TERRIBLE mess!

t
 

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Discussion Starter · #20 ·
Update. Not sure if it's the only one but the oil gallery plug definitely leaking.
Video
The sealant I used: Permatex High-Temp Thread Sealant #59235
The plug was cleaned from old sealant and seated what I thought was all the way in but looks like the sealant didn't really set or harden at all and got washed out for whatever reason.
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Looked into ordering a whole new plug with whatever the right sealant is already pre-applied but wherever I've looked, there's 2-4 week wait on them being shipped so reused the old one for now. I cleaned it all up, dried the plug and hole as best I could and seated it in again with heaps more sealant, and threaded it in a lot tighter than I had previously. Let it set overnight and will try another startup after work tonight. Will see how it goes this time around. Not ideal having the plug all the way in but hoping it doesn't leak at least. Will see if there's any other leaks downstream from there anyway.
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Really puzzled as to the correct method of installation. Looking at the old engine block, the plug sat flush with the block surface so the sealant must have been doing all the work. There's also a passage that would be almost fully blocked if the plug is driven all the way in. Judging by how 'opposite-of-well' the sealant did on my initial install, I really don't trust it to be oil-tight unless driven all the way in, so the question is, what's the right sealant to use here? What is the sealant used from factory? It looks like blue Loctite but really doubt that's what it is.
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