I’ve had an annoying oil leak in my ’96 VDP (118,000) for some time
now. This weekend I replaced the oil breather and hose to the dip
stick and cleaned up the bottom of the motor. I left the car in my
garage overnight and the thing leaked oil on the garage floor.
Anyway…to make a long story short I crawled under the car and
checked out the bottom of the engine and the rear of the sump and
front of the bell housing under the area of the rear crank seal
were covered with oil. My conclusion is that the rear crank seal is
leaking. Before I make arrangements for a shop to replace I’m going
to try some Rear Main Seal Stop Leak in a can (snake oil?). Any
thoughts…? When I was a younger man I would have just pulled the
motor out and replaced the seal myself, but now I’ve sold my engine
hoist and stand and don’t have the motivation or equipment to drop
the trans and so on…

Thank you,
Roger

 

Their are some that like these "additives" that stop leaks by causing the rubber to swell. One problem is it doesnt just swell the rubber thats leaking but all Second problem is it just keeps swelling it till it blows over time.
I prefer doing it the correct way

 

Roger,

Not common for these engines to leak from that area, but I suppose anything is possible.

There are lots of issues with the camcover seal and the "D" seals leaking and it running down the engine and pooling in that area. Mine did that, and it took some serious sealing to get that camcover oil tight. I used RTV Hi-Temp grey as a dressing on those "D" seals and the camcover groove etc.

Those snake oil thingies can help, but as said they can cause issues. I have used them is the past with mixed success, but I never leave them in there. I run it for a few days, and then give it an oil change.

 

From a practical standpoint, *if* it is the rear main seal, just add oil as required. It takes a lot of cans of oil to add up to the cost of replacing the seal.

 

Agreed to a point.

The mess on the driveway, exhaust, rear axle assembly, taillights etc is a tad annoying.

"Her" V12 is weeping from the rear main seal, 10 years now, obviously I did NOT size it proper when I rebuilt the engine, and the amount of movement on the dipstick is almsot zero, but the mess under the car is HUGE.

I wish (hahaha) there was a budget way of converting the dinosaur V12 rope seal to a full circle seal like these AJ16's, but alas it is "near impossible" and very costly. I know the '89> engines have that full circle seal, and are oil tight, but they are very skinny on the ground down here.

 

"The mess on the driveway, exhaust, rear axle assembly, taillights etc is a tad annoying" exactly! I park the car over kitty litter I put on the driveway, but it's still a huge mess and one huge PIA. I stopped in my local Advance after work last night to check out the White Shepherd and they didn’t have any. They did have the Bars Leak remedy in a bottle. I read the label, didn’t like what I read and put it back. If I don’t like what I read on the White Shepherd label (when I can read one…?) then I won’t use any cure in the bottle. I have used brake fluid mixed in with the automatic transmission fluid to stop transmission leaks in a “97 Cadillac I once owned. I may research that option. I really don’t want to spend the loot on seal replacement right now, may end up doing so in any case. The thing is I switched the car over to Mobil 1 a few months before the leak started, could be just coincidence, however...?

 

There are plenty of "suggestions" around the internet that synthetics have the effect of cleaning out deposits that once held oil back at various points in an engine. When the deposits are gone, the leaking starts. It is exacerbated by the smaller molecules of synthetics. At least that is the reasoning of the writers.

There is also the possibility that the grade of oil you are using is particularly thin in comparison to what was in the car before. That would aggravate the situation further.

You could always try going back to your old oil of choice and see how that goes.

 

I'm using 15W50 Mobil 1 and the car runs like a champ! I won't switch oil. I also run 15W50 in my '95 XJS AJ16.
Synthetic oils have strong detergents in them and I'm not really surprised that the VDP leaks. My XJS is dry and leak free at not quite 80,000 miles. I bought a small bottle of White Shepherd tonight, don't know if I'll use it. Eventually I will have the seal replaced.

 

The previous reponse was written simply to address the new information that you had switched to synthetic Mobil. There was no indication of what weight was being used.

Switching back to whatever was in the car before it was leaking was just a suggestion based upon the facts as presented.

 

To be sure, no offense was taken. As I said, I use Mobil 1 15W/50 in both cars and prefer it over non-synthetic oil. I still haven't made up my mind about using the small bottle of White Shepherd I bought. Too add to my projects the pinion seal in my XJS (80,000 this AM) is leaking and I will change that seal. Dropping the rear sub-frame isn't as much work as dropping the trans.

 

Well, as the use of White Sheperd is not well known around these parts, please be sure to come back and update everyone if you do decide to try it. Good or bad.

 

I will report back on the White Shepherd...if I use it.

 

I put the White Shepherd in my car this afternoon.It's a clear liquid the consistency of gin or vodka. Anyway, after driving around town for an hour or so the leak seems to have stopped. I'll keep watch and report back.

 

I added Barr's to a 96000 miles XJ motor that was leaking in the driveway. Worked as advertised. I took the route of changing the oil with fresh 10/40 a few days later. Now after 10 mins idling in the driveway I have 1 1/2 qts on the floor. The rear seal on my car has definitely failed now.