With regards to this common issue (of leaking rear crank seals), someone suggested not to fill the engine with more oil than half way on the hatched area of the stick. Careful here as it takes a long time for the oil to fully descend in the engine. Many, many hours more than ”one minute” as stamped on the stick.
I have several 50s and 60s Jaguars, and while some are dryer than others, I have some that will sometimes be dry and then begin to leave oil marks on the floor, and some vice versa. Mostly under the rear of the engine, as the few drops from the front end are more persistant. Often due to the 4 vertical studs that hold the cyl head to the block. They leak less with Loctite (forget the number now).
I drive my cars very often.
That was one of the reasons I changed my engine , old 3.4 was down a bit on oil pressure , slight rattle from timing chains , and a bad oil leak from the rear main !
It is worth having a good look to see where the oil is coming from .
I thought the rear main got a lot worse , but I had a pin hole in the tin sump !!
Unless for severe use, I always had my customers’ run their XKs at halfway up the crosshatching: it helps decrease some leakage, but will not cure it.
Fixing the front seal is (relatively) easy: the rear? Not so much.
The advice I’ve seen is to not go by the crosshatch before verifying it is accurate, based on the published capacity for the engine. Not sure of all of them but I believe my 3.8 is 9 qts. Then note where that falls on the stick. The engine also has to be level. On such a large pan even a few degrees off level can change the reading significantly since the stick is towards the rear. And as you say, you have to wait quite a while. I never fill mine to the top of the hatch any longer.
This sort of advice might make sense for certain engines and not for others.
For example, the XK120 and Mark VII do not have a rear seal as we think of rubber lip seals, they have a slinger scroll like an Achimedes screw.
It scrolls the oil back into the sump.
If this scroll gets full of crud it will not scroll the oil back, it will leak out.
Christ, I plumb forgot all about that!!!
So the scrowl runs into the engine not out…???
Um…yes…
Same deal on air-cooled VW egines, on the “front” pulley.
Worked astonishingly well, and when ya shut the engine off, 1-2 drips of ‘oel!’ VW thoughtfully even made a drip spout, on the pulley tin, to drain it out.
Well,
On a sailboat the rope seal aka packing gland, has to be allowed to drip or it will burn up the rope seal…
For clarification…on a boat…the engine has a shaft that runs from inside the boat to outside to the propeller…at the exact point where the shaft crosses into the water a seal is needed…this is called a packing gland…it is identical to our rear main seal…going from oil to air…and a rope is used…however on the packing gland it can be adjusted…and is adjusted…say several times a month. And there is no scroll
Generally speaking, on boats, you have a fair length of shafting either inboard or outboard of the stuffing tube, which means the seal has to deal with whiplash from any imbalance in the shaft.
Not to mention the prop hitting bits of “unwater”. Propshafts may be dead nuts true when they go into the boat… but they rarely stay that way.
The only relative motions the rear seal on a car engine has to accommodate are the rotation of the crank, and the clutch pushing against the thrust shims.
Thanks to all, and esp Rob for the picture and explanation on the old fashion rear crank seal.
I thought the early engines had that famous rope seal. When did it change from Archimedes style to rope? And then to something else?!?
As many readers know, I have many 50s and 60s Jaguars, about half of them are really dry, with barely a drop on the garage floor, even after a fortnight. I drive them very often, and always for >20 mins.
The ones that leak are both at front and rear of the crank, plus a few with non dry ODs, i changed a while ago from running full hatched area of the oil stick, to about 1/3, as I don´t want to over pressurize the crank case ventilation. And I know about the oil stick issues.
I will now pursue the Archimedes style rear crank bit…Could well be that the threads are clogged.
Peder
But then I learned that very clean threads leak more than slightly clogged ones…
my latest experiment is to remove the oil filler lid after a serious run, thus releasing any pressure in the engine.
I have very clean crank case vent filters and flex hoses, the theory being that over pressurized crank cases force oil out any possible way.
The breather on the front of the engine, the thing you remove to do a timing chain adjustment, takes care of any pressure in the crankcase.