It appears my second wife has developed an oil leak in the rear. It looks and feels like engine oil, which has me a bit puzzled. Why would there be engine oil dripping from the rear, fuel-tank area? As you can see from the picture, I have apparently had the leak for a while, the concrete stains are there to prove it.

My first suspicion was differential oil - perhaps a leaking pinion seal, but I checked all around the differential without finding any trace of a leak. It is completely dry.

I have been looking all around the bottom of the car for the leak source, without finding anything besides the oily bottom of the fuel tank. Any ideas?

 

The other oil in the area is the hydraulic fluid to operate the top rams. It usually drips in front of the right rear tire. Why the right ram leaks more than the left is a mystery.

Check the oil level in the reservoir above the CD deck.

 

If she goes topless it may be her hydraulic lift cylinder. See if the oil level in her tank is low.

 

Thanks for the tip. The oil does indeed look a bit low, just on the bottom line of the reservoir.

I suppose the hydraulic lift cylinder is what I should check next. I guess removing the back seats and right rear sidewall is required. What a drag, I just had that one out yesterday in order to install a windstopper.

 

Just wondering... I read in another thread that the hydraulic fluid level for the top should be at the bottom line when top is up, and top line when top is down. Would that be correct?

In that case, since my fluid is at the lower line with top up, I guess I'm alright.

So what the hell can this oil be then? Fuel pump has oil in it?

 

Keep in mind that leaking oil can travel backwards as it is blown along the underside at high speeds. You may need to put the car on a lift and spend quite a bit of time underneath it. Look for trace paths that the oil may have traveled from its actual leak point before it finally dripped off the chassis somewhere....

 

This was my initial thought as well, but then I jacked the car up, put on stands and went crawling all around under the car. I cannot find a single traceline of oil, all looks dry and well.

The car DOES use quite a bit of engine oil though, so perhaps there is something from further up the engine dripping during travel, the drops ending up on the fuel tank, finally making a cute little puddle while parked.

The jags... always something to worry about

 

It looks to me like the oil is coming out of the drip hole under the spare tyre from your second picture, have a look under your spare tyre and see what is there.

 

So I removed the spare wheel and found a pool of... Something, from somewhere. Next went on and removed the battery, and found a LOT of something under it. Battery fluid? It looks and smells like oil!

Could not find any leaks in the battery either, so this really has me a bit puzzled.

 

Sounds like your ragtop hydraulic fluid is leaking somewhere....

 

Reservoir for hydraulic fluid looks alright though. Levels are correct both for top up and down positions. Considering the amount of fluid that was there, and what has already been leaking onto my garage floor, I would expect to see a drop of the reservoir level?

 

My battery has been a bit weak lately as well, so I went ahead and got a replacement battery today. Old one was put into the car in 2006, so I guess it was time for a replacement anyway.

When removing the battery again, I noticed some fresh oil in the region again. Took out all the lining, trying to trace my way to the hydraulic hoses and reservoir. Nothing there, it really cannot be hydraulic oil! If it is, it must teleport its way to the bottom of the battery.

Very odd this. Oil under the battery? Perhaps my wife is playing me a trick, pouring olive oil there every night. Otherwise I'm clueless. Top works great, just as it always has.

 

Hey folks. With all this speculation the fluid is the hydraulic fluid for the top, why don't you sop it up with a white paper towel and check the color.

If it's the fluid for the top, it should be green. I don't know of any other fluid in the XK that's green. Antifreeze "should" be orange, not green.

 

+1 on checking the color. Find out what fluid you're dealing with.

 

Already did that - the color is yellow with a hint of brown, resembles the engine oil I have in her - Mobil1 ESP 5w30.

I could perhaps also suspect brake fluid, which would have about the same yellow color, but brake fluid should be less oily to the touch...

 

Doesn't look like top hydraulic fluid to me. I think the really old stuff was yellow, but what you have looks more like used motor oil. Jon89's idea that it was traveling to the rear from a front leak has some real merit.

Someone more familiar will chime in soon I'm sure.

 

Travelling to the rear, teleporting itself under the battery.

Currently my theory is pretty simple. I used to have a half-full bottle of oil in the trunk for topping up. Perhaps it leaked without me noticing, with time (even after removing the bottle) trickling down to this position. The cover for the battery did have some oil on it, but it was actually more only on the bottom part of it.

I hope it is nothing more serious than this, because on sunday we leave for a 2 week road trip in Tuscany (Italy), for some winding roads between the wineries of the Chianti region.

 

I don't think that you mentioned the oil in the trunk before. That may well be the source. I'd wipe and clean up all of the present oil as best you could and then after a couple of days you should either see no oil anywhere or else you might see it in one or limited spots, which would narrow your search.

 

That's exactly what I've done. It is all spotless right now.

Regarding not mentioning the oil in the trunk - since I didn't detect any leak from the bottle whentaking it out, it didn't come to my mind as being related. At first, I thought something underneath the car was leaking...

 

Sounds like quite the mystery. You might need to call in Sherlock Holmes. We are all looking forward to finding out the source of this mysterious oil. The part that got me was when there was oil under the spare tire. That seems to me that it can't be oil moving from the engine area. The only other thing that I know of in the trunk area would be the fluid for the top, and you say that it's not that, so it is indeed a mystery. Let us know if you ever discover the source.