Rear main seal conversion disaster?

I would check the fit of the cork oil pan seal. It shifting during assembly, or missing altogether, could explain the dry test run and the splurge once tilted back. Remedy would only entail the sump off.

To check the oil gallery end bolt, take out the rearmost side gallery bolt and fiddle a wire towards the back. If the bolt is missing (which I doubt because Dick M. has a point) the wire will eventually scratch at the flywheel.

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I think this is it, the cork seal is not there. I now distinctly remember it being left in the workbench … I know the rubber seal that fits in the sump groove is there, but not the cork one. Damn it!!

Either/or: it doesn’t need both.

You mean it takes the rubber seal OR the cork seal right?

Depending on the style of groove, in the pan and sealing ring, yes.

I cannot remember exactly what/when pan and seal ring difference was between the models, but as long as there’s one or the other and it’s properly sealed, it only needs one seal.

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Ok, so, i will eventually take that engine out… again and investigate…

Buying a bicycle is becoming an attractive option…

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Someone said 4.2s (or something like that) went to the rubber seal… but both fit. I went for the cork seal as it is prettier, and after all, it was a cork seal from the factory.

It’s either cork or rubber, not both. Pretty good idea that this might be missing.

…if you‘ve run the engine it can’t be related to the oil gallery and if you put the seal in nicely it has to be the main seal :confused:

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Last time mine was apart I had to buy my own 1/4" cork blank and cut my own. The one I ordered from a usual was less than .2 and had no squish.

Yes I’m pretty sure they switched to rubber after the 3.8 E.

They both come with the gasket kits we‘ve had before.
@MartinScherz has unipart kits from the 420/420g days that have cork but no rubber so I am a little sceptic, since my low miles 7L block also had cork. The cork does fit just the same, different machining or not. Anyways, seems rubber is generally better.

Yes every Payen kit I’ve seen has had both in it. I don’t use those kits any more though since I started using Cometic. There actually is a Cometic rear sump gasket. It’s awful, and I refused to use it. It’s super hard and doesn’t compress at all. Feels like plastic.

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It is cheaper to make the gasket kits with both pieces. The cork seal is used where the fitting groove is in the rear seal housing. The rubber seal is used when the groove is in the oil pan. You need to use the combined parts so that there is only one groove. IE: no groove in pan and rear main housing, either or, not both.

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I NEVER recall that… thanks!

The lower half of the seal seems to be nicely snug with the crankshaft (see photo, the orange stuff is antiseize compound).

But I discovered something that *may" be my salvation. The two long bolts holding the oil pan on either side of the seal housing are missing!!! May be the bottom of the threads open up inside the block…

Unless there is something wrong with the top half of the seal…

Fingers crossed…

Open bolt holes means the bolts have to be sealed at the thread too, am I right ?
These UNC threads are too rough to get sealed by itself I guess.

How did Your story end ? Asking, because I have a scroll crank at the bench and tinkering …

The pan fasteners and related parts are UNF not UNC. The UNC threads are for studs into alloy mostly.

Oh well, my thoughts were in my leaking Burmann steering box indeed (argh!), but regarding the oil pan - would UNF bolts require sealing agent there if the other end is open ?

All normal threads (maybe not the tapered ones, BSPT, NPT…) are not sealing on purpose, so all bolts that are not in blind holes require sealing.

NPT and BSPT tapered pipe thread are not considered leak tight on an engineering level. For this reason , it is bad practice to use them in fuel service without a thread sealant. It is illegal (NFPA fire code violation) to use them in flammable gas service without a sealant.

If you look at cross sectional drawing above, you will note a gap between the male thread crest and the female thread root. That creates a spiral leak path that must be plugged with a wrap of Teflon tape or some other thread sealant.

There is a class of pipe thread that does not require a sealant, NPTF, National Pipe Thread Fuel. NPTF threads are designed for an interference fit at the root/crest that creates plastic deformation. Because of this it is not considered good practice to reuse these fittings after they have been initially tightened.

All parallel thread fasteners require a gasket to seal the head of male to a suitably flat, smooth face of the piece that carries the female thread (exception: male stud and female dome nut) .The XK engines are covered in cap screws and dome nuts with copper washers for exactly this purpose.

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So they are leak tight for many purposes but not good enough for safety (or dangerous gases then)

The Borg-Warner transmissions have a tapered bolt, same as grease guns use, and it’s not a common leak source (it’s the pressure takeoff point and ATF usually finds a way out). It’s steel in cast iron, I was surprised that it sealed that well, but it does. This is why I excluded the tapered threads.

I don’t know if Teflon tape is always enough to make normal threads seal for normal purposes?

They are not considered leak tight without a thread sealant. Absent a thread sealant, they are not safe for Class 1 flammable liquids or any flammable gas. Water leaks or oil leaks are considered a nuisance, but not a hazard.

A Class 1A Flammable Liquid has a Flash Point below 73F and a boiling point below 100F. Basically, flammable liquids that readily vaporize, create a vapor cloud, at room temperature.

Examples of common Class 1A Flammable Liquids are gasoline, ethanol or methanol. Things that are not would be diesel fuel or ethanol-water mixtures below around 40% alcohol by volume. You whiskey drinkers will recognize that as 80 Proof.

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