I want to replace the rear main crankshaft seal, the flywheel o-ring and the o-ring that seals the oil pump cover. To do that requires removing the transmission, the clutch and then the flywheel.
You can see how I removed the transmission here:
This write-up covers clutch removal.
After removing the clutch, I removed the flywheel so I can get access to the rear main seal and the oil pump. If you need to remove the flywheel, you can see how I do it here:
I removed the engine from the frame, since I am powder coating the frame, and put it on my large work bench. But this work can be done with the engine in the frame.
I didn’t require any special tools to remove the clutch. That said, I did use an electric impact driver to break loose the clutch bolts.
However, you can remove the clutch bolts with a socket wrench and a large blade screw driver to block the flywheel from turning. The torque on the clutch bolts is low enough you won’t break off a flywheel tooth.
I shot a short video of the highlights of this procedure.
Since I’m going to remove the flywheel after I remove the clutch, I need to avoid a disaster involving the crankshaft front thrust washer coming off it’s mounting pins. If that happens, I have to remove the crankshaft to get it back on the pins, which isn’t a disaster but a real PITA. Should I not notice that the thrust washer is off the pins and then tighten the flywheel bolts, there is a high likelihood of damaging the crankshaft and crushing the pins that are cast into the engine block, which is a true disaster.
The way to prevent the front thrust washer from coming off it’s mounting pins is to force the crankshaft to the rear so it butts up against the thrust washer. I do that by putting a short, 12 mm long, 6 mm Allan head bolt into the recess of the alternator rotor Allan bolt that attaches the rotor to the crankshaft.
Then I install the front engine cover using the top two bolts and finger tighten them so they pull the front cover tight against the head of the short 6 mm bolt.
DO NOT OVER TIGHTEN the two front cover bolts or you can damage the alternator rotor bolt and/or front engine cover. You just need to snug them up by hand. And, it you have the earlier model front cover with a third cover bolt at the bottom, you don’t need to install that bolt.
When the M6x12 bolt is correctly installed, there is a slight gap between the front cover and the engine block at the bottom of the cover. That gap is your sign you have safely pushed the crankshaft up against the front thrust washer and you can safely remove the flywheel.
Secure Engine to Work Bench
I don’t have an engine stand, so I secure the engine to my work bench. I use a 2×4 under the front timing chest cover to keep the engine from tipping forward. I use two ratchet straps connected together to clamp the engine to the bench top by passing the strap under the bench top and over the top engine cover. This secures the engine so it won’t move around as I work on it.
I can see there has been some oil leaking out of the rear of the engine onto the shelf above the oil pan. So, something is leaking, either the rear main seal, the flywheel o-ring and/or the oil pump cover o-ring.
Remove Clutch Bolts
The clutch assembly includes the cover plate, the clutch plate or friction disk, and the pressure plate. They are secured to the flywheel with six M7x18 bolts in groups of two at the 12:00, 4:00 and 8:00 positions as shown in the picture below.
Unlike the pre-1981 clutch assembly which requires use of three hardened bolts with nuts to remove the clutch, the 1981+ clutch can be removed by loosening all six bolts and then backing them off 1/2 turn at a time in a cross-wise pattern without risk of damaging the clutch or yourself.
PLEASE DO NOT remove a pre-1981 clutch using the procedure I document here. Instead, follow this procedure for pre-1981 clutches.
–> 21 BMW 1977 R100RS Remove, Refurbish, Install Clutch
Adding Locating Marks To Clutch Parts
The clutch assembly parts are balanced so they need to go back together the way they are oriented now. I add two locating marks to the cover plate, pressure plate and the engine block before I remove the bolts.
Adding two sets of index marks is a “belt and suspenders” move on my part in case one set of marks gets erased.
I use my electric impact driver to break the bolts loose.Once I break the bolts loose, I snug them up by hand and then use a socket to back them out 1/2 turn at a time in a cross-wise pattern to gradually release the pressure on the diaphragm spring.
But if you don’t have an electric impact driver, you can block the flywheel to keep it from moving with a large blade screwdriver inserted between the teeth of the flywheel as you break the clutch bolts loose with a socket wrench.
The clutch assembly didn’t want to come loose, so I use a screw driver with some Popsicle sticks against the engine case so I could lever the rear cover plate to get the assembly loose, but not damage the edge of the bell housing.
I put the stack of Popsicle sticks under the screw driver to protect the edge of the bell housing. If this is damaged, the transmission won’t be aligned correctly with the engine and drive shaft. So, be careful if you have to lever the clutch assembly to get it loose.
After I removed the clutch assembly, I can see the diaphragm spring that sits between the assembly and the face of the flywheel. It falls right off the face of the flywheel.
The rear component of the clutch assembly (the part facing you when you remove the clutch assembly) is the cover plate. I show the markings I found on it.
Next is the clutch plate, or friction disk. One face has a sleeve that faces toward the transmission. The other face is smooth and faces toward the flywheel and has the part number and manufacturer’s marking number on it.
The third component is the pressure plate. It has ears on the side that faces the flywheel. I show the markings I found on it.
2019-11-24 Edits and typos.