I have an oil leak and it seems to be above the oil pan. It is draining down and dripping from the A/C compressor in the front, (it's not the compressor) and in the rear down the back of the oil pan (may be the oil pan). The valve covers have been resealed in the last year.

 

Add oil leak indicator dye to the oil and take a look with the Boro scope where the oil leak is coming from.
This still sounds like a valve cover leak.

 

Normally any Jaguar act "allergic" against a water pressure clean in the engine compartment, but I think with a serious issue like oil leak, this might be the second step, if you cannot figure it out without...

Hence:
1. Use a very bright torch to check, if you really cannot see the source of the leak - starting at the cam covers of course. Look from above and from underneath.
2. If that is no good, maybe use the water pressure cleaner to remove all old oil residue, while not spraying water into anything, which is water-sensitive. Then drive again and look again for the source of the leak.
3. If that also fails: As suggested above the UV dye test (I am myself about to do one on my X-Type). I bought UV-dye for R134a - see the following thread:
https://www.jaguarforums.com/forum/x...ne-oil-286703/
4. if your problem are not the cam covers and not the head gasket, it might be the front crank shaft seal or the oil pan.
5. If it is the oil pan:
https://www.jaguarforums.com/forum/x...4-2-5l-272715/

 

When I changed the oil I noticed the amount of oil. It has had a slow leak for a couple years. Just a drop or two, didn't even drip on the driveway. The leak is getting a bit worse. The valve cover gaskets were changed last year at a Jag shop. I am starting to think it's a crank seal. I will look today and use the suggestions above.

 

You know that there are 2 crank seals? A front one and a rear one...

You are loosing a lot of oil (in volume) but not much is being found under the car? That sound like your X400 is burning oil... What does the exhaust smoke look like? On reason for the burning of oil are "head gaskets needing replacement" and there is hardly any car, where swapping the head gaskets is as difficult as on the X400, as the complete engine has to come out for that - not only that: The engine has to come out from underneath...

 

Oil pan seal/gasket is a common leak and there are 2 ways to replace with pan removal.
Transfer case OUT or drill a hole in the casting 'web' to allow access to the pan bolt hidden by the transfer case.(I have done it BOTH WAYS)

At the dealer I removed the Xfer case.
In my own shop I ask the customer to make the decision.

Lots of info on the internet about the pan gasket.

 

I'm not losing a lot of oil, just enough to put a couple drips on the driveway over time. The car isn't burning any oil. There is zero exhaust smoke and I never have to even add oil between oil changes. It's a small leak. I think it's either a front crank seal or a combination of the oil pan and crank seal.

 

If one of your suspicions is the FRONT crank seal, this means that the oil is leaking in the right hand side of the engine!?
Also do not discount what motorcarman wrote: sump-seal, and I have also drilled that "hole" (a clean hole, not that kind of butchering as I saw it on youtube).

I myself am being plagued by such an oil leak - I have done already pretty much everything, and it is still leaking and I can't find the reason for sure:
- I had the transmission off 3 or 4 times (I lost count). I swapped the rear crank-seal.
- I swapped the sump-gasket, TWICE!
- I have put UV-dye into the engine oil, and I am even using an endoscopic camera.... - but I am still lost!
Current assumptions (The leak seams to be right under the rear crankshaft seal)::
a.) maybe a new sump gasket is not doing the trick and I have to heavily apply HTV, too, not just on the few spots, as per design.
b.) maybe the brand new replacement of the rear crankshaft seal is not doing the trick and needs to be changed again.

The oil leaks after driving, even after a very short drive. Once, the drops caused my that driving have escaped the engine, no further drops come out due to parking alone.