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Most BMW inline engines feature a large open sump design that allows major engine overhauls and repairs without removing the engine from the car. In particular, you can replace rod bearings and the lower oil pump nut quite easily (see Project 24). However, in order to access the engine internals, you will need to remove the lower oil sump.
Unfortunately, the gasket on the oil sump often leaks with age. Replacement is not too difficult, but you do have to remove the entire front suspension to be able to remove the oil pan. Begin by jacking up the car (Project 1), and then remove the front two road wheels. Next, remove the lower suspension components. Depending upon which engine and chassis you have, the components you must remove may vary. In general, you will need to remove the following: lower crossbrace (X-brace) if installed (Project 66), left and right A-arms (Project 59), front axle support bar and motor mounts (Project 59), front sway bar (Project 59), and steering rack (Project 59).
When you remove the front axle support bar, you will also be removing the motor mounts. This means that the engine will need support to keep it from falling out of the car. If you let the engine hang without support, you may damage the transmission—and create a dangerous situation. To keep the engine suspended, use an engine support bar that spans the strut towers (see www.101Projects.com for recommended vendors). As an alternative, I’ve seen pictures of a make-shift engine support bar—a thick 4x4 from a lumber yard that spans across the two strut towers with an eye hook that attaches to the center engine hook. This works as well, but a manufactured metal engine support is ideal. Also, if you have very tall jack stands, you can support the engine from the motor mount arms (which I did for this project). Place a jack stand under the front of the transmission for backup support if you go this route.
With the front suspension removed, you should have clear access to the bottom engine sump. Don’t forget to empty the oil from the engine (Project 2), or you will have a sudden mess on your hands when you drop the oil pan. Remove the small screws that hold the engine sump to the bottom of the engine case. On E36 six-cylinder engines, two of the bolts in the rear of the pan are somewhat hidden; there are two access holes for these bolts. With the small bolts removed, slide the pan off of the bottom of the engine. If the pan resists, tap it with a rubber mallet to break the seal of the gasket. Watch out for the oil pump pickup and sprocket near the front—they hang down into the pan.
After you’ve done your work in the bottom of the engine (welding the oil pump nut or replacing the rod bearings as detailed in Project 24), clean the mating surface of the engine block with gasket remover. Then place the new gasket on the sump and reinstall it. Bolt up the suspension and you’re finished. You may want to have the wheels realigned, as dropping the suspension can affect alignment settings.
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