BMW REPAIR (bmw_repair) wrote,

BMW Clutch Replacement, BMW Transmission, BMW Starter

One of the most difficult and complex jobs you can perform on your BMW 3-Series is a bmw clutch replacement. For that matter, replacing the clutch is difficult on just about any car. Fortunately, you're in the right place here, as I will guide you through the process step-by-step.
The first thing to do is to make sure that you need to replace your bmw clutch. On my E36 318is, I found that the clutch was slipping and couldn't move the car at all. At first I thought that there might have been a problem with the clutch master or slave cylinders, but upon further inspection, I couldn't find anything wrong. I looked underneath the car as a friend of mine repeatedly pushed in the clutch pedal. The slave cylinder and arm was appearing to work perfectly. That's the strange thing with bmw clutches - I have replaced quite a few over the years, and almost every time I take apart the old one, I have a difficult time figuring out what caused it to fail. Clutch components don't reveal their secrets too easily.

Anyways, there are a bunch of steps that you need to perform prior to replacing your BMW clutch:

Disconnect the battery
Jack up the BMW
Remove the bmw exhaust
Remove the bmw driveshaft
Remove / disconnect the shifter
With all of these tasks completed your bmw transmission should resemble

Now, move to the side of the transmission and unbolt the slave cylinder. Also, disconnect the backup lamp switch and detach its corresponding harness. Support the transmission with your floor jack and remove the lower transmission support bar (Figure 5). More details on this can be found in the Pelican Technical Article: Replacing BMW Transmission Mounts. Then, move your floor jack under your transmission and support it. We will now undo the bolts that hold the transmission to the engine.

This is where the going gets tough. First off, the bolts are special Torx head bolts which require special sockets in order to remove them. You need to apply a phenomenal amount of force to remove these bolts from the transmission - if you don't have the right tools, then you will not succeed. Get an external Torx socket set with sizes from E6 through E16, and you will be covered for all of the bolts on the car. These Torx bolts are used in applications where a good grip is required, and a lot of torque needs to be applied. The inset in Figure 7 shows two of the Torx bolts that you need to remove.

These bolts will be a huge pain to remove. See for details on the bolt locations. The ones on the side and bottom of the transmission will be relatively easy to remove - those aren't the ones that you need to be concerned about. The two bolts at the top of the engine near the cylinder head are very difficult remove - especially the one at the very top. The reason is that there is no room to easily reach these and apply any significant amount of force. In order to remove this top bolt, I used the following tool combination: 3/8 Torx socket, 3/8 1-ft extension, 3/8 extension u-joint, 3/8 3-ft extension, 3/8 to 1/2 adapter, 3-ft 1/2 breaker bar. This combination of tools was the only way I could reach the topmost bolt and remove it. I found that I could place a smaller tool on the bolt, but then I had no leverage to remove it. With this combination of tools, you basically need to hold the socket in place with your fingers and have an assistant pull on the breaker bar. Somehow I was able to use my feet to push on the breaker bar, but I really wouldn't recommend trying that.

If that top bolt wasn't enough, the starter bolts are even more difficult. Depending upon your year car, you may or may not have what is known as a threaded starter. If the starter housing is threaded, then all you need to do is remove the bolts from underneath the car. If your starter has non-threaded holes, then you need to place a wrench on the nuts that are on the opposite side of the bolts. This can be a near impossible task on the six cylinder cars. In order to reach these nuts, you will need to remove the six-cylinder intake manifold, which is a huge project in itself. I will be writing an article on this in the near future, so never fear. If you have a 318, the good news is that it is possible to squeeze your hand down into the engine compartment and reach those nuts. A photo of the nuts that you need to remove.

With the difficult nuts removed, it's time to pull the BMW transmission away from the rest of the engine. Make sure you didn't forget any more bolts on the back side of the transmission - there's at least one that holds on a metal shield. With the transmission supported on the jack, simply pull it away from the engine. If all of the bolts, hardware and accessories are properly disconnected, it should simply pull away. If you forgot something (very common), go back and double check everything. It should pull away quite easily - don't use the grip-of-death to pull it out - you could damage something. Work slowly and carefully at this point. Also make sure that the BMW transmission is well balanced on the jack - you don't want it to accidentally fall on you. Be sure that the transmission is well supported - don't let it hand on the center input shaft as that could cause it to bend. The bmw transmission pulling out of the car. Figure 11 shows the transmission removed from the car.

Now, you will want to remove the BMW pressure plate. On this particular car, I found that some of the pressure plates bolts had problems with rounding out when I went to remove them. If this happens, then dig out your trusty Dremmel tool and cut them off in about 1 minute. Don't waste your time trying vice-grips or other foolish methods - you can cut them off, and you don't need to worry about damaging the pressure plate because you're going to be replacing it anyways. When you're ready to remove the last bolt, grab the BMW pressure plate with one hand - it's easy for it to fall off when the last bolt is removed. The disc should also pop out when you remove the BMW pressure plate.

With the pressure plate removed, you should be able to see the BMW flywheel. This particular flywheel was used on a E36 318is with air conditioning. For some reason, the AC 318s used a dual-mass flywheel (probably to reduce vibrations from the high compression 4-cylinder engine). Unfortunately, this BMW flywheel can be expensive to replace - more on this later. The next step here is to remove the BMW flywheel bolts. You can use a socket and breaker bar, or simply zap them off with an impact wrench. I used a handy electric one here. With the bolts removed, your flywheel should be able to be tugged off of the crankshaft The BMW flywheel removed from the engine.

Let's talk for a moment about BMW clutch kits. With the exception of the flywheel, these kits contain everything that you need for your clutch job:

BMW Pressure Plate
BMW Clutch Disc
BMW Throw out bearing
BMW Flywheel bolts
BMW Flywheel seal
BMW Pilot bearing
BMW Throw-out arm pivot & clip
BMW Clutch alignment tool
The dual mass flywheel is two-piece and bonded together. This changes the natural frequency of the flywheel and reduces vibrations in the engine. For this particular car, I probably could have substituted a non-dual-mass flywheel, as I don't use the air conditioning system very often. The pressure plate up close along with some new pressure plate bolts. If you damaged yours removing the BMW pressure plate, you will want to replace them with new factory ones.

Now, let's turn our attention to the BMW transmission which we removed from the car. Begin by removing the throw-out fork. The fork is attached at one end with a small metal clip. Remove the fork from the transmission by disconnecting the small plastic pivot from the hole in the BMW transmission. The fork, new throw-out bearing, clip, and new pivot piece. Assemble the clip onto the pivot. Lubricate the whole pivot piece well with some white lithium grease.

Now, we'll work on the throw-out bearing guide tube. This is the small tube that the throw-bearing rides on when the clutch is disengaged. As the throw-out bearing slides back and forth on the tube, the have a tendency to wear out. A new guide tube and bmw transmission mainshaft seal. The old guide tube installed on the BMW transmission. Remove the bolts that hold the guide tube to the transmission. Remove the guide tube, and underneath you will find the mainshaft seal. Using a small screwdriver, punch a small hole in one of the indents in the surface of the seal, and pick out the old seal and remove it. Clean out the inside of the bore where the seal fits, and install the new one. Tap it in lightly with the end of an extension, taking care to make sure it doesn't go in cocked. The new seal installed, flush with the flange. Now install the new throw-out bearing guide tube, and apply a liberal coat of white lithium grease. Now, take the new throw-out bearing, place it on the throw-out arm, and attach the arm to the bmw transmission. Your throw-out arm is now ready for assembly back into the car. You might also want to clean up the input spline with a wire brush at this time.

If your back-up lamp switch is giving you trouble, now is the perfect time to replace it. Figure 40 shows the hole in the bmw transmission where the switch goes. Figure 41 shows the new switch. Figure 42 shows the new switch installed in the side of the bmw transmission. Pretty easy. Use a new sealing ring on the switch when you install it.

Now would also be an excellent time to replace your BMW starter, if you've been having problems with it. Access is very easy at this point - the removal process is somewhat difficult later on. The bmw starter is easily accessed. The only difficulty is disconnecting the wires from the opposite end. Before you even go near the bmw starter, verify that the battery is disconnected - the BMW starter has live voltage from the battery going to it at all times!

Now, it's time to turn our attention back to the flywheel end of the engine. We'll now replace the flywheel pilot bearing and the flywheel seal. The pilot bearing holds the transmission input shaft in place and aligns the transmission up with the crankshaft. To remove the flywheel pilot bearing, you may need a bearing puller. Place the puller inside the bearing and use a socket on the puller tool to slowly remove the bearing out of the crankshaft. On my 318is, I used the bearing puller, only to find out that I could have reached in there with my pinky finger and pulled the bearing out. Try pulling it out by hand before you resort to using the puller. The new bearing should fit easily inside the hole in the crankshaft. Use a deep socket to evenly tap in the bearing.

Now, using a screwdriver, puncture and remove the flywheel seal. Be careful not to damage any of the side surfaces where the seal mates to the engine case. Take your new seal and coat it with a light touch of Curil-T. Then install it onto the engine, taping lightly around the edge with the end of a 3/8 extension. Tap lightly and carefully - make sure that the seal doesn't become cocked in its bore. Clean up the left over sealant.

Now we're ready to reinstall the flywheel onto the engine. Always use new flywheel bolts, and have your flywheel resurfaced at a machine shop if you are planning on reusing it. Install the new flywheel onto the engine. Install the new flywheel bolts and torque them down. You must use a torque wrench and a flywheel lock to tighten the flywheel. I use a simple flywheel lock that is basically a strip of metal with two large slots in it. This allows you to attach the lock to a bolt affixed to the engine case, and one affixed to the flywheel, where the pressure plate bolts normally mount. This inexpensive lock works great on almost any car. With the lock in place, torque the bolts. The flywheel installed with all the bolts properly tightened to the proper torque.

With the flywheel mounted, now take your clutch alignment tool and place it in the center of the pilot bearing. Install the clutch disc. Then install the pressure plate onto the flywheel, compressing the clutch disc. Use new pressure plate bolts if you damaged them when you removed the old pressure plate. When the pressure plate is tightened down to its proper torque, remove the alignment tool. The disc, pilot bearing and pressure plate should all be aligned.

Balancing the bmw transmission on your jack, mate it back up with the engine. Be careful not to let the transmission mainshaft support any of the weight of the transmission - keep it balanced well on your floor jack. You may have to play around with the height and rotation of the transmission to get it to line up well with the engine (Figure 64). Once you have everything aligned, reattach all of the Torx bolts that you removed. Remember to use a wrench on the nuts in the bmw engine compartment if your starter isn't threaded through.

Reattach your slave cylinder, the backup lamp switch, the driveshaft, and the exhaust. At this time, I also recommend that you bleed your clutch system.
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