Rubber Rear Main Oil Seal

My 71 engine has been sitting for a long time and before then the rear main seal did leak a bit but not too bad - I am expecting it will leak a bit once I have the engine going again.

The last time I checked there was no viable modern rubber oil seal mod/kit available for the V12 but it is some time since I have looked into this. As the rest of the engine is Ok I really dont feel like dropping the bottom end to put in a new rope seal that as I understand aftermarket quality is suspect and it might leak worse than the current original item.

So is there a modern mod/kit to use for the V12 now available or am I stuck with the old rope version.



The later engines use a rubber seal, but it won’t fit the earlier engines. Ironically, though, the rope seal is the better choice! The rubber seal has a bad habit of blowing out and dumping all the crankcase oil on the road in a matter of seconds. The rope pretty much lasts forever and never leaks. If it leaks, it’s usually because the PCV system is malfunctioning, possibly because there’s way too much blowby on the pistons.

If you have to replace the rope seal, it’s better to use the Ford 460 rope seal than the Jaguar part. It’s a bit longer, have to cut it off flush when installing, and it’s graphite empregnated so it has less tendency to char if installed too tight.

And you can replace the rope seal without removing the crank. There’s a tool called a Sneaky Pete that involves a bit of steel wire that you can wrap up and over the journal, clip to the end of the seal, and pull it into place. Or, you can just leave the upper half untouched and only replace the lower half of the seal. That’s really easy, and usually fixes the problem.

Thanks for that reply full of great information. So as I previously found, a modern replacement has not been developed, If I do decide to replace it I will take your advice but I will not muck around so will lower the crank to do it.

Thanks - very helpful


Hi Gary
There are several options using modern seals for the rear.
There is a ford 2 piece one that has been used on millions of v8s
SNG Barratt sell one as well.
Terry’s in the USA also sell one.
However all these modern seals require crankshaft milling to fit.
My engine rebuilder recommended the Ford seal, which was readily available in NZ. To date several thousand miles later it’s perfect.

Thanks for that information - again good stuff - thanks.

Given my age and the amount of usage of the car, if the crank requires removal and milled to take modern seals then it would be simpler to just put a new rope seal in. It good to know there are options and I would certainly look at what you have described if I have an engine issue and the crank has to actually come out.

Great information



My car has 280000km on the clock and the only thing not leaking is the rear main seal, 1989 lip seal engine.

To revive this topic - over on the UK Club forum it has been posted that Rob Beere will do the Rear Main Mod for a V12. It was stated that the rear flange that holds the flywheel is machined so that a modern lipped seal replaces the old rope one.

Is this what 42southern was talking about? Any one with experience of this Rob Beere method? As it is not practical to send the engine to the UK is it something that can be done locally?



There’s apparently one additional alternative besides the Rob Beere modification - but also requiring crankshaft modification. There is a Ford 460 rubber lip seal that sits where the rope one does, but the spiral oil retaining groove on the OEM crank that keeps the rope seal lubed has to be welded up for a smooth surface.

See crank pictures: Modifided on the left, unmodified on the right.

When going back with a rope seal, I’ve heard stories that it’s critical… super critical to use the sizing tool to get the seal pressed into place properly as well as to pre-soak the seal for as long as possible - like a week even - before installing. Essentially the spiral carries a little film of oil to the seal and PVC vacuum keeps it in place so I understand.

~Paul K

Hi Paul and thanks for the information and pics - very helpful. Do you know if the Rob Beere method is different?



So you’re saying they build up that spiral groove with weld material and then grind it back to smooth?

My engine rebuilder told me that they mill the groove off then build up the area using some kind of welding process, to use a modern ford lip seal.
It wasn’t expensive.

It’s called subarc welding.

Cannot see how a one piece seal is working there, Other than split arrangment similar to rope, how is the seal fitted over crank flange which is much larger than rear journal.

I don’t know a lot about the Rob Beere method, other than supposedly, and inexplicably, it requires no block modifications. Only the crank needs to be sent to Rob Beere for modification.

The end result looks like:

From Rob’s site:

Thiese pics were posted by Jaguar Restorations after sending a V12 crank to Rob for “modification”

I’m at a loss to explain how the large rear seal attaches without block modification. It also kind of looks like there’s some sort of rubber inner seal being used too - like the Ford rubber seal mod. I also don’t see how they get it in there.

Yes. I suppose it could be done a variety of ways. Filled in and ground back, flame sprayed then ground, etc…

Here’s that ford rubber seal:

Compare all that to a block w/ the standard OEM rubber seal:

~Paul K

Well, that first pic isn’t a V12. Wrong bolt pattern.

It also just occurred to me that the flywheel mounting bolt holes and dowel holes on the later V12 with the rubber lip seal must be blind holes or oil would seep through the threads. I suppose the bolts could be installed with thread sealant, but I think the dowels would still be a major leak path. And by the same token, you’d have to do something if you tried to fit a rubber lip seal around the OD of the flywheel mount flange on the earlier V12 because those holes are decidedly not blind, they go clean through.

Hi Guys
Here is a pic of the ford seal used on my car, a 1971.

image image

The only crank mod was removing the scroll then building up the crank to size. No other mod required. Note Ford used it from 1973 to 1991 there must be a huge number in use.
Not a drop of oil in 4000km, chancing my luck mentioning that.


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You’re right about the pattern Kirbert. I just took the photo from the Beere website and didn’t look at that, but clearly all the other features are V12.

Picture flipped for easier comparison:

Two things I can think of… perhaps they was an early picture w. the 6cyl crank as a mock up -as it uses a 9 bolt pattern. OR… part of the modification is to simply cut OFF the 10 bolt + 2 dowel flange and re-drill the crank for the 6cyl bolt pattern?

E-type block rear (sorry-couldn’t’ find a better picture).

Paul K

Paul and the other contributors - thanks for all the pics and other information. I have to say that I am really none the wiser. The Rob Beere pics are of a 6 cylinder and I know the mod was possible for that engine but I am not convinced a similar process can be done for the V12. I appreciate the split Ford seal can be used to replace the rope seal with modification to the spiral but really why do you need to remove that - oil going up against the Ford split seal is no big issue, afterall it brought oil to the rope seal (up until this post I thought it worked the opposite like an oil slinger to keep excess oil away from the seal).

I have an old V12 out of a XJC in my backyard so I might pull it out and see what is going on and discuss with my local engineering shop.

Thanks for the pics and the input - most enlightening.



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when rebuilding my 1978 V12 in 1994, PerHE engine , i spent a lot of time on the rope seal installation!
i have replaced many older cars with rope seals, never had a come back!

on mine NO oil leaks at rear seal for about 1000/1500 miles , then around 2K very slight and it got worse as miles came up!
leaks now about a quart in 500miles , seems to settle there , SO its far to much work to fix , i run it 1 quart low, SO BE IT !
im thinking as the aluminum block gets hot the main bores enlarge and the crank walks around a few thou. and wallows out the rope bore!
also a vacuum in the case is deiffenatly requiered , problem there is some oil ends up in the inlet manifolds, PCV stuff?

About par for the course, and about the best one can hope for, using a rope seal.

Were I to have taken Tweety’s engine completely down, I would have converted it to a modern lip seal.