Tools

¼" Ratchet with short extension
10mm socket or open ended wrench
Thin and medium blade Flathead screwdriver
Fresh Coolant
New thermostat and O-ring
Small rag
Shallow pan to collect spilled coolant

Procedure

1. If it has been determined that your 325/325e needs a new thermostat, you're in for an easy and quick job.

2. To remove the housing, you'll first need to remove the hose exiting the thermostat housing and going to the lower part of the radiator. Have the shallow tray below the car to catch any spilled coolant. Move the hose to the side.

3. To get to get to the thermostat, you'll need to remove the housing, which is held in place by three 10mm bolts. You'll need the short extension to be able to get to the last bolt at the bottom of the housing.

4. The housing may be a bit stuck in place, but a tap with a hammer will break it loose. Again, expect some spilled coolant, which the shallow drip pan has saved your clean up again.

5. You'll now see the thermostat, which may be stuck in the engine side of the housing. Use the thin bladed screwdriver to pry it out. If this doesn't work, a pair of channel locks will pull it lose.

6. Remove any old O-ring still left in the housing, and grab a rag to wipe the area clean. Get your new thermostat and O-ring ready for reinstallation. Not e the orientation of the thermostat and the O-ring when you remove the old thermostat. Directions for installation will come with the new thermostat.

7. Take your new O-ring and put it around the new thermostat, and place it into the housing. To ensure a good seal when retightening the housing, tighten each of those 3 10mm bolts a little at a time until all three bolts are retightened to specs as found in the Bentley manual (not available to me at the time).

8. Reinstall (Replace if necessary) the lower radiator hose onto the thermostat housing, and refill coolant to its level.

9. Start the car and allow it to reach operating temperature, leaving the radiator cap OFF. When the thermostat opens, you may need to add additional coolant to its proper level.

10. Check for leaks around the housing and around the hose you removed. If all is well, take it for a drive AFTER you replace the radiator cap (of course), and check to make sure you have heat and are not overheating.