Serious oil leak on my '89 XJ40


After just finishing the repair of one of my door handles (which was a serious pain and psychologically traumatic) I have now discovered that my car has a nasty oil leak.

For the past several years I’ve had a very small oil weep coming from between the rear of the engine and the automatic transmission. I even went so far as having the rear main crankshaft seal replaced
which seemed to do the trick. Although the smallest of an oil leak in that area never really completely went away :neutral_face:

Now when the car is running I actually have a drip of oil coming out of the same area. I’ve eliminated the cam cover and cylinder head as a suspect.

So the transmission is coming out once again but then how will I be able to tell if the leak is coming from the new rear oil seal (not that big a deal) or the oil pan gasket (a much bigger deal) !!! The car has 165K on the clock and still runs and looks like new … seriously.

Groove I had a similar leak on my '94 6 plus years and 25,000 miles ago. I wasn’t up to tackling that situation so I turned it over to my independent master Jag mechanic. After a couple of false starts it ended up being an oil plug in a hole (as I understand it one used for line boring during manufacture) in the rear of the block. The fix involved pulling the engine from the car. I wish I could better explain this but that was my understanding at the time.

I think if the rear main seal is leaking you should be able to see the ‘tell tale’ oil trail running down from above the oil pan gasket, if not,
I’m not sure if this is possible, but can you run the engine up to operating temp with the transmission removed from the car ? If you can do that you could clean around the suspect areas with spray on clutch cleaner then when it is all nice and clean it would make spotting the source of the dripping much easier.

Maybe pressure-wash the underside so its all spotless … then, if you still can’t determine the origin of the leak, tape or adhere somehow a series of shop towels here and there and run the engine. One of them will be oily.

Gentleman, a most joyous holiday greetings…

All excellent ideas !!

Casso … I also thought about the possibility of running the engine with the transmission removed to tell if the leak is coming from the rear main oil seal or the gasket pan. The only problem i can think of is the transmission cooling lines, but with those disconnected and capped there is nothing pressurizing them … I think :smiley:

Larry … I gave the entire area a spotless cleanup while the car was up on jacks. The leak is definitely coming from above the junction where the transmission connects to the engine. I could actually see it slowly weeping down out of the joint.

Mike … Can you remember anything else about that rear oil plug and why the engine had to be removed to replace it ?

Screenshot 2022-12-17 at 6.34.15 PM

1 Like

I agree, The trans oil is pumped from inside the tranny through the cooling tank at the front of the car, so with the tranny removed they shouldn’t be under any pressure, capping them would be easy or maybe you could just raise them up higher than the cooling tank. Whatever method you choose I hope it all goes well and you get the leak sorted easily :+1:

How do you start the engine with the transmission removed?

I don’t know, that’s why I said I’m not sure if it is possible, but providing the starter motor can be fastened and engaged I’m fairly sure it would run without the transmission in place, or perhaps you know otherwise ? If so now would be a good time to let Grooveman know.

From memory the top bolts thread is in the bell housing, so probably not a goer.

I don’t have any more info but plan to call the master mechanic tomorrow morning and see if he can enlighten us. The work was done 6 plus years ago but I know he keeps work orders on file.

If that is the case, and that is the only ‘snag’ the top bolt could be substituted for a nut and bolt of a smaller diameter as a temporary measure.

There ya go, thinking outside the box :smile_cat:

Hmmm …

But wouldn’t the big flywheel the starter uses to turn the engine still be in the way ?

Thinking outside the box? How about this: Remove the flywheel and bolt a large (6-10"?) PVC pipe cap, with ‘one way’ (angled) teeth cut into the open end, in its place. Take another pipe cap, cut mating teeth into it, and affix a large bolt through the center such that an air wrench can engage it. Mate up the two pipe caps, have an able-bodied assistant twist the key to the start position, and goose the air ratchet to (hopefully) spin the engine. Once the engine rpm exceeds the air ratchet rpm the angled teeth in the pipe caps will allow the one to override the other. Crazy, huh? :scream: Now for the legal part: attempt this at your own risk, knowing I have never attempted this, nor would I, as I have zero - zero - training as an automotive engineer (although my late father was a mechanical engineer, and I did stay at a Holiday Inn Express, one night, many years ago).

Well …

No because the bolt would still be in the same position with or without the bell housing in place.

Robin …

What I meant and didn’t say was wouldn’t the flywheel be in the way to observe a leak at the rear of the engine while it was running, which would be the whole purpose of this exercise :cowboy_hat_face:

1 Like

Had a pretty good oil leak on my 2003 GMC Yukon 5.3 liter engine…for 2-3 years. Took maybe 1 quart every 2-3 months.( 1,000 miles) At one point, while having a new water pump installed, mechanic brought it to my attention. Says its either the rear main seal, the tranny oil cooler hoses (which fit right by the oil filter, or the oil pressure sender (on top of and at the rear of the block).

So, not the sender…I looked. Leak got worse…now about a quart every 500 miles. Underneath the vehicle was a complete mess…60 days ago. Oil and road dirt. Oil drips on the grass…big yard…no concrete drive. Cleaned it all up underneath…couldn’t tell a dang thing. Two options left…seal or cooler lines. Called GMC dealer…my engine has no tranny cooler…ha…therefor no cooler lines. One option remaining…rear main seal.

$900 later. new seal, new cover plate…no oil leak. A little thinking, and then you just gotta bite the bullet. SD

1 Like


There no method of cooling the ATF? That’s like the old days!

My bad. No oil cooler. Therefore, no oil line connections to leak back at the leaky area. SD