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Full disclosure: I don't have an XK, but I'm hoping someone in the XK section may have run across this issue. Not gotten any responses in the XJ section on this question...
Long story short: 2006 4.2L, started out with zero oil leaks. I changed the oil pan gasket and the oil filter adapter gaskets as preventative maintenance, as they're going on 20 years old now. Dec 2024 I replaced the pan gasket with an OE Jaguar part. Fast forward to August, I found the pan was seeping badly, oil all over my undertray. I thought I had just gotten a part that sat too long, or maybe I torqued it wrong. Replaced that gasket with a Mahle gasket at the end of 2025. Torqued per FSM spec.
April this year I found it's still dripping. 2 weeks ago I wiped off the oil pan and tray, put it back together. Drove about 25 miles and it appears to be coming from one bolt in particular. At least this narrows down the area of concern.
All the bolts on this pan should be into blind holes (no oil should seep around the threads). I'm thinking either:
1. the pan somehow got damaged/bent in the first removal
2. the surface of the pan against the gasket is too rough or has old gasket stuck to it.
Anyone have experience with this? I did wipe the pan off both times, but I did not scrub or sand it in any way. Of course the only check for warpage is to remove the pan again and put it on a true surface. About ready to just throw money at the issue and buy a new pan and gasket from Jag
May that be either from a leak above that point, or maybe oil from somewhere in front of it blowing onto that spot while driving?
The entire edge of the undertray padding appears gooey and I assume that's the leading edge of the pad? Seems something is blowing rearwards to me.
Our 2006 XK 4.2 has a plastic pan rather than a metal one. I believe that all the ZF 6HP boxes in the XK's were fitted with plastic pans on the production line. Has you changed yours for a metal pan or is yours not a 6HP?
These pans do not normally leak because the bolts are quite closely spaced. However, they do need to be tightened in a diagonal pattern starting from the centre of the long side, especially the metal versions.
If it was fitted correctly with a new gasket and clean surfaces, I suspect the oil might be coming from somewhere else. If you have a good sense of smell, you will be able to distinguish engine oil from gearbox fluid.
May that be either from a leak above that point, or maybe oil from somewhere in front of it blowing onto that spot while driving?
The entire edge of the undertray padding appears gooey and I assume that's the leading edge of the pad? Seems something is blowing rearwards to me.
The foam pad sits under the frame crossmember in the photo, rear of the oil pan. The leak is definitely not coming from above the oil pan, I checked to confirm the sides of the block are 100% clean. The oil is leaking from the rear portion of the oil pan, and then it's blowing back onto the bell housing and transmission. THe oil is dripping from around the bolt with the red arrow.
For clarification: the bolt with the arrow is at the rear of the engine, the crossmember is behind the oil pan but in front of the bellhousing. Sorry for the confusing geography.
Our 2006 XK 4.2 has a plastic pan rather than a metal one. I believe that all the ZF 6HP boxes in the XK's were fitted with plastic pans on the production line. Has you changed yours for a metal pan or is yours not a 6HP?
Yeah, the transmission has a plastic oil pan. The issue I'm having is with the engine oil pan.
Last edited by mhamilton; Apr 29, 2026 at 07:00 PM.
Yeah, the transmission has a plastic oil pan. The issue I'm having is with the engine oil pan.
I do apologise. I've never heard of anyone changing the engine sump gasket on an leak-free car as a preventative measure. That is a classic situation where "if it's not broken, don't fix it", applies 100%. As you had already changed the gasket, I assumed that it must have been the gearbox sump as removing that part is a maintenance item.
As mentioned, the leak is definitely not coming from above the oil pan, the sides of the block are 100% clean. The leak is from the oil pan gasket. For clarification, that is oil dripping off the head of the bolt in the attached photo.
I do apologise. I've never heard of anyone changing the engine sump gasket on an leak-free car as a preventative measure.
No problem! We do not have the preservative weather conditions of the UK in the US south. High heat conditions will kill gaskets and plastics in far less than 20 years.
Last edited by mhamilton; Apr 30, 2026 at 09:17 AM.
Im going to ask the hard question. Did you use a pry bar to remove the pan from the block? The sure fire way of testing the pan is to place it upside down on your workbench.
(I hate voice recognition... sorry about the nonsensical bit. Corrected.)
Im going to ask the hard question. Did you use a pry bar to remove the pan from the block?The sheer far away of testing the pan used to place it upside down on your workbench.
Basically yes--I used a wide screwdriver, the pan was significantly stuck to the block during the first removal. I did not pry so much that I thought I deformed the pan, but I'm thinking either the pan is slightly bent or there is something wrong with the surface of the pan that is preventing a seal to the gasket (old gasket stuck, corroded metal, etc).
Just visually there's no obvious bends in it--I'll have to put it on a true surface and check closer. The pan is such thick steel, I thought it would be pretty resistant to any deformation.
Last edited by mhamilton; Apr 30, 2026 at 11:14 AM.
Well, there's your answer. A screw driver is never the right tool to use for prying. And now I wonder if the mating surface on the block was marred.
Best remove it and take it to a machine shop for straightening or get another one.
Well... not sure that is the definitive answer. I didn't jam it in there and twist it like a mad man. I gently nudged the pan off from one of the edges. I'm also assuming (but don't really remember) I pried at the front edge, since it's far more accessible than prying against the rear where the leak is occurring.
But I do agree, it seems this is a rather esoteric issue that will require removal to diagnose.
So not a single spec of oil above the pan? I thought the same. I had a very minor leak right bank valve cover. Don't catch it checking for vacuum leaks, didn't see anything though there's almost no way to see it. I ran down the block - I should say dripped. and between the block and oil cooler. My pan looked exactly like yours. I was sure it was the pan leaking. Block 'looked' dry from every visible angle. Changed the pan gasket, ran engine dye through. Looked good. Next season, same damn thing. Looked like the pan. If I would have removed the cooler, I would have spotted it.
My scope didn't have the flexibility to catch it. I ran my fingers under the valve cover - nothing, then one spot. the spot at the top where you put the RV. Wet oil.
If you're certain it's not that, then you should just change the pan and be done with it. The pan it cheap and @guy probably called it. No one here can give any better opinion.
FWIW, you show the drip but not where it's coming from. That's where it's leaving. The frame is soaked. I hope you get it sorted.
So not a single spec of oil above the pan? I thought the same. I had a very minor leak right bank valve cover. Don't catch it checking for vacuum leaks, didn't see anything though there's almost no way to see it. I ran down the block - I should say dripped. and between the block and oil cooler. My pan looked exactly like yours. I was sure it was the pan leaking. Block 'looked' dry from every visible angle. Changed the pan gasket, ran engine dye through. Looked good. Next season, same damn thing. Looked like the pan. If I would have removed the cooler, I would have spotted it.
My scope didn't have the flexibility to catch it. I ran my fingers under the valve cover - nothing, then one spot. the spot at the top where you put the RV. Wet oil.
If you're certain it's not that, then you should just change the pan and be done with it. The pan it cheap and @guy probably called it. No one here can give any better opinion.
FWIW, you show the drip but not where it's coming from. That's where it's leaving. The frame is soaked. I hope you get it sorted.
I didn't take any pictures of the sides, but yes from my inspection of the block there is zero oil on either side or down the back. The sides of my block are readily visible. The frame is actually not soaked (I know it looks like it in the photo) but that is the result of me cleaning everything with solvent.
This past week when I took the photos above, after I cleaned everything I rolled up a piece of Pig Mat to wedge between the rear of the oil pan and the frame. I'm going to drive it a week or so and re-inspect. I'll try to get more photos then. I'm hoping also that having the PigMat in place will show the leak more clearly, instead of having oil blow around. When left unattended for months I was finding oil spray back on the bell housing, transmission pan, etc. Cleaned all of that off and will recheck.
The UV dye is a good idea, I can add that if there's still any. Honestly I wish it was coming from the valve covers--mine are still original and I was almost tempted to do them out of preventative maintenance as well. But will get this sorted out first.
I do appreciate all of the replies. My intent with posting wasn't to get a magic 8 ball answer, I know we can only tell so much from forum posts. But I was hoping to eliminate the possibility of some issue with the bolts themselves seeping, or if someone said "yeah you have to really scrub the gasket surface" then I would know I did something wrong. But all the info I've found on these pan gaskets it's basically slap-and-dash and nobody has persistent issues. So I agree, either the source of the leak is not the pan or something is wrong with my pan.
4.2L oil pan persistant leak
