This thread is to get feedback: have others had to replace the mainseal, what's a reasonable cost, what other work should be done while the car's apart? From my search, it seems like this a pretty uncommon problem.

The story: I had my 2007 R56S (only 45k miles) on jackstands recently to install an intercooler. When I was under the car, I noticed a slow (apparently) oil leak. It wasn't clear where it originated, but I could see oil dripping from the bottom of the transmission. At the time, I thought (probably naively, that the worst case was the turbo oil line). The underside of the car was pretty dirty with oily vapor and road-dust.

Today I brought the car in to Bay Bridge MINI (who seem great), and they diagnosed the problem as likely being caused by a leaking mainseal. For today, they pressure washed the car and asked me to come back in a few days, thinking it would be easier to confirm the oil leak was from the mainseal after the car had been cleaned and run for a short time (the leak is slow - I never have to top-up oil between changes - so I don't think a few days is going to be a catastrophic problem). I understand that this is a pretty major repair effort if it is the mainseal.

The cause of the problem is a bit of a mystery to me. I don't think the car has been massively over-filled with oil (I check pretty regularly, even after changes). I know that there have been a few periods where the car has sat for 4-6 months (hence the low-mileage on a 2007). Is this a seal that can dry and fail if the car isn't moved for a while (lately it's been getting full-time use)?

Do you have any comments on: possible causes, whether this is a common problem, what other maintenance or upgrade work should be done simultaneously?

I am considering replacing the clutch, even with the low mileage and no signs of deterioration. What do you think? From reading on here, it seemed like a stock clutch was about as good as anything else (I've read about several of the people who've had bad experiences with Giken).

 

If it is a slight rear main seal leak, you could decide to wait till a clutch is needed therefore the labor would overlap. Its really not a common problem and its also possible that its and input shaft seal leak on the trans. Either way if you decide to have them go in and fix it, do your self a favor and have both replaced at the same time. There should basically be no change in labor and a small difference in parts. This could save you a ton in the future.

 

Thanks for the suggestion. I'm glad the shop suggested cleaning it and then taking a look. Hopefully that will make it clear whether this is a slight leak or something more severe (or if it's actually coming from somewhere else). I'll probably do the clutch at the same time, I guess.

Is there anything else worth doing at the same time? I haven't had the turbo oil line replaced. Presumably this would make that job a lot less work, no?

 

I'm betting its your input shaft seal leaking. Not hard to tell the difference between motor oil and gear oil (75w90). Eventually you will have address it, or it will address you with a nice slipping clutch.

 

Thanks for the suggestion. I'll probably stick around next time it goes up on lifts and check if it's the input shaft seal. Updates to follow.