2003 Mini Cooper S
129,000 miles

Yesterday, I changed my Crank Sensor O-Ring, the Drain Plug, the Oil Pan Gasket. It's been leaking for awhile, but for the past week, it's been leaving a sizable amount on the driveway daily.

After changing them all, I checked this morning to see if there's been any leaks, and, unfortunately, there's still a leak there. However, I'm sure that the oil pan gasket and the crank o ring needed to be replaced. They were obviously bad when I removed them.

The leak is coming from two areas right were the oil pan meets the transmission. It's so strange to see the leak here as there isn't a gasket there that I can think about. Maybe it's leaking at the lip of the gasket there and coming down inside the pan? I got under there with some brake cleaner and cleaned everything up and am able to visibly watch the oil seep out.

Here are some reasons (maybe not valid) that I don't think it's the rear main seal:
1. I didn't see a flow of oil from the transmission when I pulled off the oil pan
2. There generally isn't much of a buildup of oil in there
3. The clutch was replaced in 2016 before I bought it. It was done by a local Mini mechanic here in Atlanta. The paperwork doesn't mention the replacement of the rear main seal, but, wow, if it wasn't done, he would have to be the biggest idiot in the world.
4. A friend mechanic told me that rear main leak is a pressure leak, meaning, it only leaks when the car is on. This leak comes when the car is not on at all. It litterally just seeps out without the engine running.
Any thoughts would be great!

 

Welcome to NAM, moved you to the Gen1 Stock Problems/Issues section which is the right place to find help.

Posting your model (R50, R53, etc.), year, and mileage is always a good idea when seeking advice. Welcome to NAM!

 

Thank you so much!! I'll make sure to pay attention and include that information next time!

 

Really, any of the components (seals, gaskets, etc.) on the MINI engine are "pressure leaks," as they all reside above the pan, so the only way they leak is from oil pressure in the running engine.

The only things that can leak a "sizable amount" of oil on your driveway without the engine running is a crack in the pan itself, or in the least, from an improperly tightened or cross-threaded drain plug.

Below is a list of items, top to bottom, prone to leaking engine oil on an R53. I've left off the Rear Main Seal, as it's not 'prone' to failing as are the others on the list. Most, as you can see, reside above the oil pan gasket. It was only after I changed all of these that I had a dry engine, devoid of leaks.

Valve Cover Gasket
Spark Plug Tube Seals (4)
Camshaft Position Sensor o-ring
Crankshaft Position Sensor o-ring
Timing Cover Gasket
Timing Cover Crankshaft Seal
Oil Housing Gasket
Oil Cooler/Exchanger o-rings (2)
Oil Pan Gasket
Oil Drain Plug

 

It is only possible to have a positive pressure build up from blowby if someone defeated the PCV. The pressure can fold the lips of the crankshaft seals.

The other possibility is if the rear seal has been replaced, it was installed crooked. A Mini specialist here has done that during a performance FW/clutch job, only have to tear everything apart to do it properly again. Remember if the rear crank seal leaks, the flywheel will block the oil from entering the clutch side. Most of the oil will leak out at the seam of the clutch/gearbox mates to the engine.

 

So, I did change the oil pan gasket and the Crankshaft Position Sensor o-ring. This resolved a large part of the oil leak. There is still some oil that seem seems to be accumulating on the bottom of the oil pan on the pulley side (which is very relieving). I'll update when I find it and fix it.

 

Other likely suspects are the valve cover gasket and the oil filter housing.

We had a similar leak showing up at bottom right rear corner of the oil pan. After replacing the valve cover gasket, it appears the leaks have stopped. Still have my eye on the oil filter housing to see when it starts to weep.

 

Thanks for the info! Thankfully, both were replaced last year. I'm still on the search! Working two jobs makes time really limited. I'll update when I find the source.

 

Check that main seal but you would have to separate the transmission from it. If you are doing a clutch job then you are in there anyway. 11111492244 is the oem part number which is linked in the thread

https://www.northamericanmotoring.co...ts-needed.html