This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your BMW 3 Series. The book contains 272 pages of full color projects detailing everything from performance mods to timing the camshafts. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any 3 Series owner's collection. The book was released in August 2006, and is available for ordering now. See The Official Book Website for more details.
BMW cooling systems have been known for being troublesome for quite some time. One of the principle areas of failure are the thermostat and water pump. Overheating problems are common on these cars, and if your engine overheats, you may find yourself having to replace your head gasket, which is not cheap.
Begin the process by gaining access to your thermostat. This requires the removal of the fan and belts, as well as the removal of all coolant from the system. See the following technical articles for instructions on how to get to this point:
- Removal of all coolant from the system
- Removal of the accessory drive belts
- Disconnect upper radiator hose
With all of your equipment removed, the front of your engine should resemble Figure 1, and you should see the black plastic thermostat housing. Remove screws that attach the housing to the cylinder head. Pull off the thermostat housing (Figure 2). It may require just a little bit of force to remove if it's caked on there. The thermostat can be pulled out of the head now (Figure 3 - shows the head removed from the car). Figure 4 shows the backside of the thermostat.
Install a new thermostat into the cylinder head using a new o-ring to seal it to the head (Figure 5). The thermostat should fit snuggle into it's bore in the cylinder head. Make sure that the o-ring is seated properly (Figure 6), and that the small vent hole or arrow faces up. Use a new seal on the thermostat housing (Figure 7). If your head has been damaged by corrosion and electrolysis (Figure 8), then you may want to add some black silicone sealant to the thermostat housing when you install it (Figure 9). Figure 10 shows the thermostat housing remounted with an appropriate amount of squeeze-out from the black silicone. Figure 11 shows the thermostat housing reattached to the head, and the flywheel sensor cable correctly routed around the housing.
Well, there you have it - it's really not too difficult at all. If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. Your continued support directly affects the expansion and existence of this site and technical articles like this one. As always, if you have any questions or comments about this helpful article, please drop us a line.