After first long test run of 100 miles in my just acquired 2004 XK8 I found a badly leaking rear main seal. Oil was flowing from the plug in the bell housing and covering the transmission pan, and when I removed the plug about a quarter of a cup of oil was there. I cleaned and degreased and toped up the engine oil and was heading a mechanic, but first I had to go and have new tires put on that I had already paid for. When I got back from tire shop (about a 20 miles round trip) no more leaking oil and inside bell housing dry?

Maybe it only leaks when very hot on long journey or maybe a dry gasket rehydrated itself. Anyone think they know what happened and as it maybe an on then off situation is it worth trying a gasket treatment in the oil?

 

with a Jag, the two Xk8's I have owned, NOTHING that broke, leaked, what ever, ever fixed itself.

 

When my rear main seal was leaking I bought some Lucas oil stop leak. It did reduce the leak somewhat, but the viscosity was so high that I was not comfortable about using it, and went back to just using 10W40 after about 1K mi.

20 mi. is not a good test as the leak will increase when the oil is hot. Just keep an eye on it and try to estimate the amount of leakage vs. loss of oil. I put up with it for three years and only changed the seal when I decided to put the car on the market.

There is a oil gallery just above the main seal that has been known to leak, but that's not as common, and still requires removal of the transmission to correct.

 

Oil leaks rarely (ie; never) cure themselves. "A Jaguar that does not leak oil, probably has no oil in it".

 

UPDATE. Today a 200 miles in 95 deg temp freeway journey and NO OIL LEAK! Can anyone explain this? Maybe the car was overfilled and the oil gallery dumped it out or something like that?

 

I've actually had two Chevrolet's after sitting for extended periods of time would leak. After driving them again the gasket would re-hydrate and quit leaking. I think you answered your own question in the first post.

 

The Jaguar gods have smiled on you.
Continue to speak nicely to them, and just keep an eye on it.

M

 

Having owned a transmission shop for years I know a little about rear main seals. As RCsign said seals can start to leak when they sit awhile basically seals do dry out and they start to leak. When they get warm they expand and a leak can stop.

If you ever had a transmission problem when the unit is cold, like slow engagement. It's because the internal seals start to harden up with age. After the unit warms up the seals expand and everything works great. It's referred to as morning sickness (makes sense).

So all that said, the rear main seal is on it's way out. Could it last without leaking for awhile? Absolutely, but, you are on borrowed time. Thing is it could be a long time? Good luck and hope it's later than sooner.

 

Seller (who I have no redress against as there is no problem now) did tell me car had a failed oil cooling hose and lost all its oil. Was towed to shop for repair and so may have sat without oil for a few days and "may" (seller says not) have been driven a few miles while leak was in progress. This was just before I got car no miles on it by seller. IF this explains the problem onset what does it say about the future life of the seal?

 

Yes and you could win the lottery. Go buy a ticket... Because your chances are better with the lottery than your Jag fixing itself. LOL.

 

I'm a bit new to the Jag scene to be any authority but am a mechanic by trade. I have seen cars do exactly this, leaking badly from the rear main on long high speed runs but not at all around town.
The cause can be crankcase pressire either from excessive blowby or the crankcase ventilation sustem being blocked. I have seen both and obviously the later is preferred.
I dont know what sort of PCV system these cars have but would probably be worth a look

 

Thanks Lilbro. Please will someone explain the XK8 crank case ventilation system and how to inspect or test it.

 

Try this link. Its a technical bulleton on the subject of cleaning them
They are referred to as a part load breather and a full load breather. I am not sure but there was discussion of them changing to a PCV system in 2004. Maybe some one else can confirm.
I cant check mine as it is still stranded 60km from home until my new oil cooler arrives from the UK.

https://www.jaguarforums.com/forum/a...-600-03am3.pdf

 

Thanks but I have responded to this advice before. This is only relating to the 4l engines up to 2003. The 4.2 liter 2004 I have has a PCV valve. I am told that if I have no codes all is well and no need to inspect.

 

The bulletin is valid for 4.0L XK Range vehicles from '97-'01, ending with VIN A13614. The 4.2L, V8 with Six Speed Transmission, was introduced for the all new 2003 MY Normally Aspirated XK8 Base Model, and the XKR Super-Charged Model, beginning with VIN A30645-A36873. 2004 MY VIN begins at A36874-A42347, my VIN is A34265 which is ~3600 units of practice on the all new 2003 MY platform, before assembling my car. As far as codes, the need to inspect should always be present, just because it has not tripped a code yet does not mean it is all squeaky clean inside, or that the sensor is still functioning correctly. An example of the latter would be the coolant reservoir sensor, if the float jams up, a coolant leak could develop with catastrophic results, and no low coolant warning script or red light present. Because of the known problem with the float, when I check the coolant level, I am more interested in the condition of the float sensor itself, than the coolant level, as it is always full.

 

Is there a sticky on cleaning or checking the coolant float.

 

Here is a link for cleaning and testing the probe. Keep in mind that this was on a '99 model, and extreme degradation of the probe. I only check to ensure that the float's movement is unrestricted, and the magnet has not dropped off to the bottom of the tank when I check the coolant level.

http://www.jagrepair.com/CoolantTank...ing1999xk8.htm

This link is from the list of 5 'STICKIES' at the top of the post page labeled 'XK8 & XKR 'HOW TO' / DIY Repair & Maintenance Links / Facts & Data'

 

Oil seals leaking on old jags are common, BUT one of the most common cures
is often overlooked, that is, crankcase pressure relief, read my blog on positive crank case pressure fix, just posted on this site.