Series 3 Leaking Rear Mains Seal

Hi All,

Seeking you’re learned opinions.
My Series 3 E has had an ongoing leak from the rear mains, which I had hoped would get better over time, since I first purchased it a couple of years ago, but alas it has been steadily getting worse to the point where it is now streaming oil out after a spirited drive. The car has only done around 5,000km since a complete rebuild, but I can only conclude that the rear crank rope seal was not installed correctly by the PO.
I’ve now dropped the sump, whilst the engine is still in the car and removed the rear lower bearing cap to find the lower seal half to be almost smooth and appeared to almost be glazed. I can only assume that it was not sufficiently lubricated prior to install and may have been scorched. I’m guessing the top half of the seal wouldn’t look any better, but it’s removal would entail an engine out job which I was hoping to avoid.
All opinions received to date, suggest that the only way to do the job properly is to remove the engine, and I don’t disagree with that, but wanted to explore other avenues first.
So my question, would replacing the lower half seal only, likely to stem the oil leak by maybe even half or slow it to a few drips or is that just wishful thinking? Have read about the use of “Sneaky Pete” but don’t know of anyone that has had success using this method.
At any rate I figured it is worth a go to replace just the bottom half seal and with a bit of luck I may have some success in stemming the BBQ smoke emanating from the louvre’s when stopping at the lights, before I go down the path of an engine removal involving 100 plus hours of work to replace a $4 part. :unamused:
Any other thoughts or suggestions would be greatfully received.


Where in the Antipodes are you?
I guess you’re right; you have nothing to lose replacing half the seal.

Just tap on my profile pic and you’ll see where in the antipodes, I be. :wink:

Also, I’ve read somewhere that the top half of the seal may be pinned and therefore cannot simply be pushed or pulled over the top of the crank, thus necessitating and engine out scenario, if it were to be replaced. Is this true?



In addition to dropping the engine, dont you also have to drop the crankshaft to replace the seal. My engine is coming out soon and when the engine is out I would like to replace the seal as a precaution but no keen on dropping the crank.


Hi Gary,

Yes you most definitely have to drop the crank to do the job properly. If you are going to the effort of pulling out the motor, you have to go all the way. Taking out the motor will be a last resort for myself as it will be such a long and delicate operation so as to ensure that nothing is damaged or scratched as it is in such a concours state, save for all the oil pouring out. :unamused:

Thanks John - taking the engine/gearbox unit is not big deal just a couple of hours work. Then dropping the crank is a different issue - mine only weeps a little so if the crank has to be dropped there is a lot of work as a precaution.

Good luck


John what was the outcome of your leaking rear main seal. Did you try just replacing the lower half and if so did it reduce the oil leak?

Andy S2 with leaking rear main seal

Hi Andy,

I would have been happy if it just reduced the leak, but it in fact stopped it all together. Needless to say I’m really pleased about that! Yes, just replaced the bottom half and took the chance, as doing the top whilst in situation, would have involved dropping the crank and it still would have been very awkward.
Took a lot of careful fettling, fitting it, then removing several times so as to ensure that it was just sitting right, with just enough clearance.
Lucky that with the V12, you can do this by removing the rear crank bearing cap, which can’t be done on the XK engine without removing the entire engine.
Photo of operation can be seen here.
Sweet As…


That’s amazing: I wouldn’t have bet a nickel that would have worked: glad that it did!

I did the same many years ago on my 4.2 6. It did stop the leaking. Some will say it can not be done on the 6, but there is a way. As a last resort for a leaking seal try AT-205 seal re-new it works.

Good to hear Glenn. Have heard of many that tried but failed. Wouldn’t have thought it’d be that straight forward on the XK engine.

John, congratulations on your “Hail Mary” approach that worked so well. I’ve never taken an XK engine apart before (lots of MGs) but I would have thought it would have been easier but you say that the crank bearing shoulder is in the way. I don’t even know what that is.

Andy S2

Hi John, I had this problem 15 years ago with my 1973 S3 2+2. I used the sneaky Pete method to replace the complete seal The engine was in the car, with the pan removed. The seal was the Ford 460 type, ( 1968 to "78 )… as noted by Kirby P in his XJS bible !. I did post some stuff at the time but I have now no record of it. As I recall, the most tricky part was to remove the old seal from the top of the crank. The process involved heat, and finding a way to push the old seal around in its grooce( it was compacted and hard ) around in its groove.The crank had to be rotated at the same time as pushing the seal slowly around its groove with a helper slowly moving the crank manually. The sneaky Pete was then used to pull the new seal around the top groove. I think it is beneficial to rotate the crank while doing this so that you don’t stretch the seal.It needs to be compacted as much as you can .The same applies to the lower half of the seal. The comments by Mr K on pages 58 and 59 are relevant. It is also important to ensure that the crankcase ventilation is up to spec. My engine does not leak when running , but does drip a bit when parked. Mr K is somewhat sceptical about this method of seal replacement, but in my case it seemed worthwhile. The whole process needs lots of patience !!! Hope this helps …John H.

Glenn, I have never replaced the seal, and hope I never need to. But how did you do so on the 6 cylinder engine? From what I see, the rear seal carrier is bolted in from the top. Were you able to access those bolts from above to remove them? And did you replace the entire seal?