Well, I got so sick of this leak, which seems to only be worsening, that I got down into the engine compartment (engine cold, of course) with a penlight to see what I could see in more detail last night. Shining the light near the area of the oil dipstick and trans dipstick/filler tube, it appeared that the oil has been dropping down from a location just inboard of the trans. filler tube, as that is where I could see that the center of the oil puddles are located on the pavement. Today I was sitting in traffic and even noticed some burning smoke coming out from the passenger side of the car, from underneath the engine compartment (note that this is on the opposite side of the compartment from the trans filler tube). Of course, this smoke could have been from when I added some oil and a can of Barr’s Leak the night before, assuming I had spilled a bit on the engine cover. Also, the wind might have been blowing in a direction that gave an incorrect impression of where the smoke was actually coming from in the engine compartment.
Any idea where this is coming from, now? btw, I tried twisting the dipstick tube in case it was loose and causing the leak, but it was tight. Also, I don’t know if this is related, but some time back I was riding Superblue though an automatic car wash. When I put her driver’s side tires in the groove between the pair of guide rails at the start of the process, I heard and felt a disturbing metal-on-metal clunk and hard jolt. I remember I asked the car wash tech, who was guiding me through the procedure with his hands, if it looked like the rails had hit anything underneath the car, but they apparently didn’t hear me (or didn’t care, if they did). The car went about 2’ or so down the rails before I experienced a similar sound/sensation. I would have gotten out of there at that point if I could, but there was no way to back out, so I let the traction system take me through the rest of the way in the car wash and, fortunately, no more of those incidents occurred. I had never had this happen before with my ‘95 XJS coupe (or any of my other models of Jags). I’m wondering now if the rails hit something low in the lubrication system on the driver’ side, knocking something loose, possibly an oil cooler line (?)
If you hit somewhere during the wash hard enough to do serious damage there must be visible evidence.
Lift the car up and inspect.
As for the leak:
What is it, engine oil or transmission fluid ?
Give the engine and under carriage a good wash, drive the car for a while, put some carton under the car, let it overnight and inspect.
Once you find where it’s coming from you will know how to fix it.
Thanks. In my original post way back when, it is definitely engine oil, and at least a coffee saucer-sized puddle when and where ever I park it. The location is about mid-way between the sides of the engine compartment, just back from the radiator a bit towards the firewall. I wish I could get the car up in the air, but I don’t have a lift or drive-on ramps. I have recently bought one of those handy “Lizard Cams” though and should be able to look up from underneath, snaking it along the ground., to hopefully spot the source.
i’ve only found oil leaks by raising the car and climbing underneath with a light. Then try to trace it up. Puddles on the ground could be from anywhere.
Don’t know much about Jag oil leaks, but all my other car leaks which were that big were either a camshaft seal, or an oil cooler line.
Maybe I missed something, but in the first post you were talking about leaks at the rear of the engine. Now you’re saying it’s just aft of the radiator. Which is it? Or, maybe more than one leak?
If it’s up front, I’d be think of a front crankshaft seal.
As you know car leaks can be really easy or really-y-y hard to track down. The hard ones almost always involve detective work under the car. Without that it’s like calling your doctor and telling him you don’t feel good and based solely on that statement expect him to tell you the problem.
First rule of thumb, fluids always drip down because of gravity, and always run back because of airflow. So any areas ahead and above the oil residue can be ruled out as the culprit. As previously posted here you need to get the car up and get your hands dirty. A lift is ideal, a jack and car stands will also get the job done.
Use brake cleaner, paper towels, and brushes to really give the bottom of the engine and transmission area a thorough cleaning. While you still have the car up let it run for a while then shut it down and wait. Any leak visible? If not you’ll have to drive the car for a while then put it back up. Because you’ve done such a great job of cleaning the bottom of your car the area of the leak should now be very obvious.
I spread out large plastic trash bags under the car before I start spraying the brake cleaner and always use eye protection.
i use carb cleaner. I wouldn’t recommend brake cleaner. All it takes is one squirt the wrong direction, lands on your paint, and you’ll be quite upset.
A tech that worked on my XJ-S for many years once told me he doesn’t clean up first. When he found my rear engine leak he showed be the track down from the cam oil feed fittings. He maintained the track is easier to see because it washes the grime off on it’s way down.
Sorry for the confusion, Ed. From the look above looking down at the puddles, it appears to be coming from just inboard of the trans filler/dipstick tube.
Oh boy … I didn’t even think about the pan, but possibly an oil cooler line. Which one is closer to the ground on a '94 4.0 coupe? On the assumption the leak could have been caused by impact(s) from the car wash “rails” around the left wheels when I prepared to enter the wash, which would be in the path of them?
If the tranny dipstick is on the left (as it will be on XJ-S after 1978 or so), that puts it close to the oil filter. It might be it’s leaking around the canister, or the gasket where the filter is mounted to the block, or fittings in that area.
I remember I asked the car wash tech, who was guiding me through the procedure with his hands, if it looked like the rails had hit anything underneath the car, but they apparently didn’t hear me (or didn’t care, if they did). The car went about 2’ or so down the rails before I experienced a similar sound/sensation. I would have gotten out of there at that point if I could, but there was no way to back out, so I let the traction system take me through the rest of the way in the car wash and, fortunately, no more of those incidents occurred. I had never had this happen before with my ‘95 XJS coupe (or any of my other models of Jags). I’m wondering now if the rails hit something low in the lubrication system on the driver’ side, knocking something loose, possibly an oil cooler line (?)
The location is about mid-way between the sides of the engine compartment, just back from the radiator a bit towards the firewall. I wish I could get the car up in the air, but I don’t have a lift or drive-on ramps. I have recently bought one of those handy “Lizard Cams” though and should be able to look up from underneath, snaking it along the ground., to hopefully spot the source. 
From the look above looking down at the puddles, it appears to be coming from just inboard of the trans filler/dipstick tube.