This really a fairly simple DIY, the only difficult part is working in tight spaces. This should take 2-3 hours if you take your time. You'll need:
- Either a 3/8" or a 1/4" ratchet
- Ratchet extensions (at least 6")
- A universal joint for the ratchet
- For the hose clamps, I highly recommend an 8mm ratcheting wrench
- (If no ratcheting 8mm wrench, you'll need a small flathead screwdriver)
- Large flathead screwdriver for bleeder screw and radiator drain plug
- A pick with a hook to get the clips off the coolant hoses
- Jacks/jackstands/etc.
- 1 gallon of BMW antifreeze mixed with 1 gallon distilled water
- A 2 gallon or larger bucket to drain the antifreeze in
- Get your car up on jack stands or ramps
- Make sure the car is cooled down so you aren't draining hot coolant
- Open the hood, and remove the plastic air duct between the intake and the air filter. It just pulls out from either end.
- Get under the car, and remove the splash shield. There's about 10 M8 bolts and two plastic rivets that have to be removed.
- Place your bucket underneath the radiator, on the driver's side. The pink and blue plastic plug is where the coolant will be draining out:
- Get a large screwdriver, and unscrew the blue plug all the way out. Coolant will start draining now.
- Up under the hood, unscrew the cap from the coolant expansion tank. Also take your large screwdriver, and unscrew the plastic bleeder screw that is next to the cap you just removed. You don't need to unscrew it all the way, 5 turns or so is fine.
- Once all the fluid has drained, you can screw the blue drain plug back in the radiator. You'll need your bucket to catch the rest of the fluid that will come out when we start disconnecting hoses. If you really want to get all the coolant out so there is less of a mess, you can remove the plug from the engine block and drain the rest of the coolant. I didn't do this.
- Underneath the car on the passenger side, you'll need to get the oil cooler hose out of the way. It just takes one bolt (10mm hex). This is the hose, already pushed out of the way:
Now you should be able to see the water pump (barely). It is the black plastic piece behind the sway bar:
- Now is a good time to remove the wire that is going to the thermostat. I just inserted a small screwdriver into the clip and just pulled the plug out.
- Now it's time to start disconnecting hoses. There's 4 hoses that connect to the thermostat. 2 have hose clamps, 2 have retaining clips. I found it easiest to get the hose clamps off using the 8mm ratcheting wrench. There wasn't enough room for a regular ratchet, and there wasn't enough room for a screwdriver either. I can't say much for this step besides this is where you'll spend most of the time. Just remember how you got the clamps off, because you've got to put them back on eventually too.
For the retaining clips, I found the one on the small hose easiest to remove by getting to it from the top of the engine and reaching down with a hook-shaped pick. For the larger one, I got to it from the underside with the same pick.
The large hose takes some considerable effort to remove from the thermostat. It has a large o-ring inside of it that is gripping on to the thermostat. I don't have much advice besides pull hard. I removed the retaining ring entirely, because I kept accidentally pushing it back on while I was trying to get a good hold on the hose.
Keep in mind there will be a bit of coolant that will come out of these hoses when they are removed. Keep that bucket and some rags handy, and wear something to keep your eyes coolant-free.
- Once you finally get all hoses removed, you just have to remove the two bolts that mount the thermostat to the water pump. This is where you'll need the 10mm socket, universal joint, and a 6" extension:
- You can snake the thermostat out towards the front of the car and then down. Remember how you did it, so that you can get the new one in there.
- I hate to use this line in a DIY, but installation is the reverse of removal. There is literally nothing different. My only tip is to get the large coolant hose back on the thermostat, put a bunch of rags or other padding on the metal cross member, and use that as a fulcrum against your forearm. After I figured this out, this gave me enough leverage to pop the hose back on. Don't put the splash panel back on yet.
- After all hoses are connected, and the wire is clipped back in, and that cooler hose is bolted back to where it should be, now is the time to fill your coolant back up:
- Make sure that blue radiator plug was put back in
- Make sure the bleeder screw (next to the fill cap) is still loose
- Start pouring in coolant. I needed about 1.5 gallons. You should fill until you see coolant coming out of the bleeder screw area. The expansion tank will be almost overflowing when this happens. This is ok.
- Screw the bleeder screw back in. It's plastic do don't screw it down tight, just snug. When you feel resistance you are done.
- Put the cap back on the expansion tank.
- Get in the car and turn the key on (but DON'T START IT).
- Set the air to the hottest setting (94 maybe?). Put the fan on the lowest setting (but not off)
- Hold the gas pedal down for about 10 seconds, until you hear the water pump start up.
- Set a timer for 12 minutes so you know when it is done. Now is a good time to get back under there and inspect for leaks.
- After the water pump bleeding cycle is done (~12 minutes), open the coolant cap and top it up. If you have to add a lot of coolant, I would recommend re-doing the bleed process. If you only add a little, you're probably ok.
- Put the cap back on the expansion tank, put the plastic duct back on, and put your splash shield back on underneath the car. Remove the jack stands & you're done.
- Clean up & wash your hands so that the smell of coolant doesn't taint your beer.