Guys,

The automatic transmission oil cooler on my 2008 Cooper S was leaking from the top so I changed the out the leaking gasket and the lower gasket as well. Its real easy and access is actually good. ITS EASY! If you can change your Mini's oil, you can do this too. Don't get ripped off by the dealer.

Here is how to do it.

You need the following 2 o-rings from Mini stealership or ECS Tuning. They are freaking expensive. MSRP is $27 and $9 at stealership. I got them for $15 and $5 from the dealer cause I have a nice smile. Part 24117551094 and 24117551093. The "shims" are the washers that fit under the bolt head. Large on on the bottom, smaller on top. You don't need new ones, just reuse the originals.






First: Remove the air filter and intake tube into the air filter as well as the air into the turbo. Youll have plenty of room this way. Its one Torx 25? on the left (passenger side) of the air filter housing to pull it off and then a screw driver to loosen the air pipe into the turbo from the air filter housing along with 2 electrical connections. The PCV tube has a plastic lock that captures it in place. You just pry it up with a screwdriver. Sorry I didn't take pics of that process. You'll have plenty of room now as per the pic:



3. Listen, if you only want to replace the small o-ring under the H10 bolt holding the oil cooler in place you don't need to disconnect the coolant lines. Just pull the bolt up and pick out the old o-ring. Install the new one after you've covered it in a little transmission fluid and torque the bolt back down to 35NM (Newton meters). Remember: Small metal washer on top of larger metal washer, under the bolt head.

BUUUUT if I was you I'd just do both at the same time while you are at it. If one is leaking the other ain't far behind.

So, first pinch off the coolant lines with locking hose clamps. Mine are metal but you can get cheaper ones made from plastic. See them clamped. Mark one of the coolant lines with a marker so you remember which nipple on the cooler it goes to.



Now you'll need to remove the coolant lines from the cooler. Undue the metal clamps. I have the specific clamp removal tools but pliers will work fine. Those pliers look like this:


The hoses are likely adhered to the nipples after all these years, so I would have these tools at the ready to help remove the coolant lines.



Then use the H10 to unscrew the bolt.



Here's the bolt:



Pull the cooler STRAIGHT UP AND OUT WITHOUT DRIPPING coolant onto the exposed transmission! You don't want to contaminate transmission oil with coolant. Put your fingers over the coolant line nipples or maybe use a rag to cover the entire cooler as you pull it up and out.

It looks like this under the cooler:



Now clean all the mating surfaces and remove and replace the o-rings. You can see the washers and the small o-ring and the large o-ring under the cooler in this pic below. Also see a little metal tab protruding from the bottom of the cooler in this first pic, at 6 o'clock.





My small o-ring looked frayed. The large one was flattened and dry compared to the new ring.

If you put your fingers over the two nipples you can flip the cooler over to change the large o-ring without spilling any coolant out of it.

Once you've got the cooler o-rings in place (make sure you lube them with some trans fluid), place the cooler back onto the transmission.

The large o-ring has ears to keep it place. Tuck those ears into place to assure a good seal. See the ears:




Remember, the cooler has a particular orientation when mated to the transmission because there is a small hole on the bottom of the cooler that needs to line up with a hole on the trans where the trans oil pumps into the cooler.

That little metal tab I spoke about above should be touching the transmission. See #2 in pic below. If you just use a large marker to paint the orientation of the cooler on the trans BEFORE YOU START, you wont have to worry about messing this up, but the tab is also there for that very purpose. The pic below is from the PASSENGER side so it will look different when you're looking from the front of the car.


Here is a pic (below) take when I'm leaning over the engine from the front. Phone is sideways, sorry. Anyway the tab it resting against the trans right under the bolt head.



Now feed the bolt in by hand and then just torque to 35NM.

Reconnect the coolant lines and hose clamps and use some brake cleaner to spray all the spilled oil off the trans.

Reinstall the air filter housing and hex bolt, cold air pipe into the filter housing and the turbo air pipe and PCV pipe and its plastic gate lock thingy and the 2 electrical connections.

Now, you're gonna need to bleed the little bit of air you introduced into the cooling system so leave the radiator cap off, turn the car's heat to high and let her run until she reaches operating temp (I know...we have no temp gauge - BMW, you are retards!-, but I have an aftermarket temp gauge). Slow process....yawn....

You might want to release air from the head via the plastic screw next to the vacuum pump.

Note: I didn't add any transmission oil because I spilled like a couple of teaspoons and I only added a 1/4 - 1/2 cup of coolant to coolant bottle to make up for the tiny bit of coolant I spilled.

After you've driven a little check for leaks. Trans oil is pushed up by the trans pump into the cooler to exchange heat with the coolant. If its gonna leak its gonna do so under high RPM when pressure is high so check for leaks after some high RPM driving.

Torque specs: