For those of you with a TIS...
The TIS instructions for removing the thermostat are incorrect for at
least some VINs, and assume the engine has a belt-driven fan rather than
an electric fan. (Bentley fans will be gratified to know that the
Bentley book has it right. I should have used mine!)
While it is (just barely) possible to remove the thermostat with the fan
and shroud in place the job will go much faster and will be much easier
(trust me on this) if you remove them first. Take out the four plastic
locking rivets that secure the intake piece over the fan shroud by
pulling out their center pieces. Then there is a Torx bolt on the right
side and a plastic locking rivet on the left of the fan shroud. Remove
the bolt, pull the center piece out of the rivet and remove it,
disconnect the two connectors on the right, and pull the fan shroud
straight up and out. This will make doing the thermostat very easy.
To remove the thermostat itself unclip and remove the electrical
connector and hoses, take out the four bolts, and pull it straight
forward. Torque the replacement to 10NM.
You'll need approximately 2 quarts of coolant if you mix it 60/40.
Don't forget to bleed the system.
In the lucky-for-once department, remember all those bad E46 thermostats
in the 2000-2001 timeframe? I bought a new part number spare back then
and two gallons of BMW coolant, based on the certainty that it would
fail on a weekend when I needed the car right after the warranty
expired. Defying all probability, the one in my car never failed...my
new car came with the new part number...and the thing sat on my shelf
all this time. Yesterday the one on my wife's car failed at about 80K
miles, and I finally got to use it! What are the chances...?
(80K...hmmm...think I'll buy another spare for my car, which is fast
approaching 50K miles.)
Though I did not write it down and don't remember it, OBD-II code was
straightforward (something like "coolant does not reach regulated
temperature") and the thermostat failed by opening prematurely. The
temperature gauge showed low, and the engine never got over 160F.
With the new thermostat, the temperature varied from 178F to 208F as it
was mapped for varying load conditions. Those of you who whine about
the computer-controlled temperature gauge, take note! If it were a
simple gauge, the 30-degree temperature excursions that are normal would
make it difficult for most people to interpret. BMW definitely got this