[Ohio Enthusiast]

I replaced the water pump and thermostat today on my automatic M-Sport 2011 E93 335i. I followed the great guides here and videos on YouTube. I noticed that some things are a little different on my car, presumably because it's an LCI convertible with the N55 engine. I've seen many guides for the N52 naturally aspirated engine and for the N54, but almost nothing for automatic LCI 335i, and nothing about the convertible.

Here're some tips:

Automatic cars:

1. Heat exchanger to remove the radiator fan - Automatic cars have a heat exchanger that is held to the radiator fan with a screw. That screw is accessible from the bottom of the car. Without removing it you can't pull the radiator fan. There's another screw holding the heat exchanger hose to the radiator. This one doesn't interfere with anything and there's no need to remove it (it's also mostly hidden by the hose so you can't confuse it with the one on the heat exchanger).

N55 engine (might be the same as the N54, but I didn't see much mention of these):

1. Charge pipe to remove the radiator fan - The lower charge pipe on the driver side is attached to the radiator fan with a big rubber block. I couldn't figure out a good way to disconnect it and ended up accidently breaking the tabs on the charge pipe that grab onto that rubber block. I also disconnected this charge pipe from the "normal" charge pipe (the one that tends to burst and is commonly replaced with an aluminum aftermarket one) and removed it from the car completely after removing the intercooler. This helped with removing the fan.
2. Remove intercooler - I also removed the intercooler (a bit harder to do with my M-Sport bumper vs. other videos I've seen) which made removing the radiator fan easier.

Convertible:

1. Underbody braces - The convertible has underbody braces that are in the way of dropping the sway bar. I didn't remove them completely, but I did remove the big bolt at the end of the brace and the 2 smaller bolts in the middle of the brace (total of 2 big and 4 smaller bolts). This allows the braces to droop down enough to get the pump and thermostat out and in. I also needed to remove the black metal cover to reach the two big bolts.

General tips:

1. Remove return hose assembly - I removed the radiator fan completely from the car (I was also doing the Mickey Mouse flange, but it you don't you can leave the fan propped half way up the car). I saw folks running into clearance issues with the hose on the left side of the car (right side when working on the radiator fan from the front of the car), and one breaking the barb where the small coolant return hose is connected. On my car the return hose used a one time crimped clamp, so I just removed the entire hose assembly with the return hose attached. There are 3 quick-connect connections that are fairly easy to undo (plus another one on the other end of the return hose that goes to the coolant reservoir).
2. Lubricate quick-connect o-rings - There are conflicting opinions about this, but I applied a little bit of plumbers' waterproof grease on the o-rings of all the quick-connect connectors (2 for the thermostat and the 4 on the hose mentioned above). This makes sliding them back in super easy - push the spring clip back in place, then push the connector back on the barb. It slides in effortlessly and there's a satisfying click as the spring clip latches on. Prior to lubricating them I struggled to get even a single unobstructed connector back on. Lubricating with coolant did nothing to help.
3. Screwdriver for hose clamps - The hose clamps on the thermostat and water pump hoses are best loosened and tightened with a screwdriver style tool, rather than a ratchet. I saw one video using a flexible driver which would have been ideal, but I was fine with a fixed one and a couple of long extensions. Explore all possible ways to hit the clamps - I ended up doing one of the water pump clamp from the left side of the engine next to the turbo (there's an opening to stick your hand in and it nicely aligns with the hose clamp).
4. Third bolt from the front - With the radiator fan removed, you can access the third bolt of the water pump from the front with a very short extension. My E12 socket was a 3/8" drive, so I used a 3/8" to 1/4" converter and a 1/4" ratchet. It was pretty tight but doable. I could even use a 1/4" torque wrench to tighten that bolt, although I couldn't do the extra 90 degrees with any accuracy so I went a little good-and-tight on it based on the feel of the other two bolts. I sat on the floor with my legs under the car, looking through the bottom of the grille and reaching from under the bumper to move the ratchet.
5. Didn't reuse the coolant - I planned to reuse the coolant I drained, but I ended up getting crud in the drain pan from the coolant running down dirty parts and debris falling into the pan and opted to discard it. I did purchase the kit from FCPEuro that include a gallon of coolant (which I diluted with a gallon of distilled water). I ended up filling in about a gallon and a half of mixed coolant and still have a little over half a gallon of mixed coolant left.
6. Disconnected radiator fan behavior - I forgot to re-connect the radiator fan after putting the car back together. When turning the ignition on to do the bleeding procedure, the water pump kicked in immediately. When I connected the fan it kicked into high speed until I turned off the ignition. This resulted in a code (31E9) that I cleared, and after that had no further issues with the bleeding procedure.

Ended up taking me quite a bit longer than most folks, around 8 hours total including breaks. Don't know if I'm just slow or if the above differences accounted for the extra time.