BimmerM3inGA
07-11-2007, 12:31 PM
I’ve been noticing lately that the clutch in my 1998 M3 with 108K miles seems to be engaging very early in the pedal travel. As soon as I lift the pedal off the floor, the clutch starts to “grab”. As a consequence, I have to push the pedal all the way to the floor to get it to disengage. Not only is it annoying, but it makes the car very difficult to drive smoothly. There could be more than one cause for this problem. The first, and easiest to fix, would be the need to flush the hydraulic fluid (there could possibly be air in the system). Second, the master or slave cylinder could be faulty. Third, the clutch could be in need of replacement.
The hydraulic clutch system is a relatively simple affair. A line runs from the brake fluid reservoir to a master cylinder attached to the clutch pedal. When the clutch pedal is pressed, a piston inside the master cylinder forces brake fluid through a second line to the slave cylinder. The slave cylinder is attached to the outside of the transmission, just behind the bell housing. It has a piston inside the pushes on a short rod (or “plunger”) that, in turn, presses on the clutch release lever. A spring attached to the clutch pedal returns the pedal to its neutral position and releases the pressure from the master and slave cylinders.
I already bled the lines and checked the slave cylinder, and checking the clutch itself is a major (and expensive) job. So replacing the master cylinder is the next logical step in trying to resolve this problem. After replacing the cylinder, the clutch feel is better, but still not how I want it. At nearly 110K miles, it’s probably time for a new clutch anyway. And that’s probably what it’s going to take to restore normal clutch feel.
Like every other E36 car that I’ve driven, the clutch pedal creaks constantly. Since I’d be doing 90% of the work involved in fixing the creak, I decided to take care of that at the same time. I’ll also cover that procedure, so you can just tackle that portion if that’s all you’re interested in.
This particular job isn’t all that difficult, but access is a challenge. There were some choice curse words directed toward some clutch components during this procedure! You have to contort yourself into the footwell while looking up into the dashboard – not easy to do! There were many times when I couldn’t see what I was doing and work at the same time. So I had to take a good look, and then work by feel. If you have access to a lift, it may help.
http://www.creative-pro.net/bmw_diy/MasterCylinder.jpg
This is what the master cylinder looks like.
So, first things first: If you have a Bentley manual, leave it on the shelf for this job. The procedure outlined in the manual is not only flat out wrong, but it’s impossible. It must’ve been written for a different model. With the exception of bleeding the system after you’re done, the entire job is performed from within the passenger compartment – not from inside the engine bay as described in the Bentley manual. I also must apologize in advance for the lack of good photos. It was extremely difficult to get photos as I worked. I did the best I could, but it was either too dark, or there were too many obstructions for the camera to focus. Plus, it’s kind of a cheap camera, so that probably didn’t help!
The first thing I would advise would be to pop the hood, and use a suction pump or turkey baster to get as much brake fluid as possible out of the reservoir. Once you disconnect the fluid inlet to the master cylinder, any fluid “above” it in the system will drain out. So the more you remove now, the less you’ll have to clean up later.
Next, remove the lower dash panel on the driver side. It is held on by two screws below the instrument cluster and one along the edge next to the center console. Disconnect the wire for the footwell light and door chime. The edge of the panel near the firewall fits into slots. Make a note of them so you can reinstall it in the proper position.
If you look up into the dashboard, you can see the clutch apparatus. The clutch pedal assembly is a single piece of molded plastic that pivots on a pin about a foot directly above the actual pedal (this is where the creaking comes from). The master cylinder attaches to the pedal about midway up, and the master cylinder is attached to the car with two bolts. The master cylinder attaches to the clutch pedal with a pin and clip. Remove the clip by grabbing the end with needle nose pliers and twisting slightly as you pull. With the clip off, push out the pin. The clutch return spring is attached to the clutch pedal with another pin, but is just seated into a notch at the other end. It will fall out when you pull the pin for the master cylinder. As I took everything apart, I cleaned and greased every moving part.
http://www.creative-pro.net/bmw_diy/OldMaster.jpg
The master cylinder is held in place by two bolts and the inlet and outlet line fittings. Pay attention to the position of all the bits so you can reassemble it later.
To ease access to the master cylinder (and to address the creaky pedal) it’s necessary to remove the pedal assembly. You’ve already done 90% of the work at this point, so you might as well take the extra couple of steps. The assembly is held on the pivot pin by a clip identical to the one for the pin in the master cylinder. Remove it in the same fashion and slide the assembly off the pin.
http://www.creative-pro.net/bmw_diy/RetainingClip.jpg
These clips hold the clutch pedal assembly and master cylinder rod in place. They are easy to remove - once you figure them out.
Thoroughly clean all the nasty dried grease from the pin and bushings and slather on fresh grease. There are two bushings on the pedal. Both of mine had slits in them, but I’m not sure if they are supposed to be there. I didn’t want to wait for new parts if they were, in fact, not supposed to have slits. So I just reassembled it using the old parts. It would probably be a good idea to order new bushings and have them on hand when you do the job. I used a white lithium grease because I didn’t want to take a chance of the grease attacking the plastic bushing or pedal assembly. I’m not saying that’s only product to use, but it seemed like the best choice for me. Set the cleaned and greased pedal assembly aside.
http://www.creative-pro.net/bmw_diy/ClutchPivot.jpg
This is where the clutch pedal pivots (and creaks). Clean thoroughly and grease before you put it back together.
Next remove the two bolts securing the cylinder. The lower bolt threads into a nut, while the upper bolt threads into the bracket that hold the brake and clutch pedal switches. Pay attention to the orientation of the bracket or you’ll tear your hair out trying to figure out how it goes back in (ask me how I know!).
http://www.creative-pro.net/bmw_diy/OldMaster.jpg
This is the same photo as above, but I wanted to show the mounting bolts again.
Now it’s time to get dirty. Place a disposable plastic bowl under the master cylinder to catch the brake fluid that drains out, and put several layers of paper in the floorboard to catch any fluid that spills out of the dish. Keep some paper towels on hand as well. If your fluid hasn’t been flushed in a while and it gets on the carpet, it will stain it (again, ask me how I know).
The two fluid lines are held in place by small metal clips. There are very easy to remove and install. When you are holding the cylinder in your hand. Up under the dash with limited access, it’s a different story. So it’s a good idea to practice a few times with the new cylinder to see how the clips work and the best way to release them. There is a flat spot where a flat-blade screwdriver can easily slip under the clip. But it’s not easy to access on the installed part. So some practice will definitely help. When you’re ready, release the clip for the outlet line first (bottom fitting). Try to let as much fluid as possible drain out. When it’s finished draining, twist the cylinder around to gain access to the clip for the inlet line and release it. More fluid will drain out and run down your arm. Why does brake fluid feel hot when it touches your skin? These parts are plastic, so use care when handling them.
http://www.creative-pro.net/bmw_diy/ClipRelease.jpg
These little metal clips hold the inlet and outlet lines in place. They are easy to remove once you learn how to release them - but it's not obvious with your head twisted around under the dash - so practice on the new one first.
Once the old cylinder is out, install the new one in reverse order. If you paid attention to the various bolt and bracket locations, reassembly shouldn’t present too much of a challenge – except for the return spring. The top end must be properly seated in its notch and it’s tough to compress the spring by hand and force it into place. But it can be done with a little determination and patience. Remember to grease everything that moves!
http://www.creative-pro.net/bmw_diy/ReturnSpring.jpg
I couldn't get a photo of the upper perch for the clutch return spring, so my illustration will have to suffice. The red portion is the end of the return spring and the gray portion is the metal bracket into which it fits. The lower end of the spring attaches to the clutch pedal with a pin and clip, but he upper end just sits in this perch. The spring must be compressed by hand and put in place after the clutch pedal and master cylinder are in place. It takes some force and cussing, but can be done.
Once the cylinder is installed, it’s time to refill and bleed the system. If you don’t have a pressure bleeder, I highly recommend adding one to your parts order. It’s well worth the $55 asking price. Since you drained most (if not all) of the fluid from the reservoir, you must bleed the brakes as well as the clutch. I’ll give a quick rundown of the brake bleeding procedure, but won’t go into a lot of detail since there’s plenty of info out there about it already. Start by attaching your pressure bleeder to the reservoir and filling the bleeder with your favorite DOT 4 brake fluid (I like Valvoline SYN Power). Pump up the pressure bleeder to 20 PSI and remove the right rear wheel. Open the bleeder valve until clear, bubble-free fluid flows out. Next is the left rear, then right front, pumping up the bleeder in between each. The left front is last, but leave the wheel off after you finish bleeding. The last thing to bleed is the clutch, and you can’t get to the bleeder with the wheel on (unless you are using a lift – then it won’t matter). The slave cylinder has the bleeder valve on it, and it’s just like the bleeder for the brakes. Crack it open with a 7mm wrench and wait for the bubbles and old fluid to drain out. If you aren’t using a pressure bleeder, have a helper CAREFULLY press the clutch while you open the bleeder. With the pedal on the floor, close the bleeder, then release the pedal. Repeat until there are no more bubbles. To thoroughly bleed the clutch when not using a pressure bleeder, it’s best to remove the slave from the transmission and rotate it until the bleeder if pointing up. Then bleed it again – this ensures that no air remains in the lines. But BE CAREFUL – DO NOT press the clutch without pressure on the end of the plunger. Hold it in your hands and keep the plunger pressed in. If you don’t, the internal piston will pop out and you’ll have to replace the slave cylinder. This is why it’s highly recommended to use a pressure bleeder! When satisfied that all air is out of the system, reinstall the slave cylinder and put the wheel back on.
Put the cap back on the reservoir and you’re done. Now go wash the brake fluid out of your hair and have a cold one. You’ve earned it! :alright
The hydraulic clutch system is a relatively simple affair. A line runs from the brake fluid reservoir to a master cylinder attached to the clutch pedal. When the clutch pedal is pressed, a piston inside the master cylinder forces brake fluid through a second line to the slave cylinder. The slave cylinder is attached to the outside of the transmission, just behind the bell housing. It has a piston inside the pushes on a short rod (or “plunger”) that, in turn, presses on the clutch release lever. A spring attached to the clutch pedal returns the pedal to its neutral position and releases the pressure from the master and slave cylinders.
I already bled the lines and checked the slave cylinder, and checking the clutch itself is a major (and expensive) job. So replacing the master cylinder is the next logical step in trying to resolve this problem. After replacing the cylinder, the clutch feel is better, but still not how I want it. At nearly 110K miles, it’s probably time for a new clutch anyway. And that’s probably what it’s going to take to restore normal clutch feel.
Like every other E36 car that I’ve driven, the clutch pedal creaks constantly. Since I’d be doing 90% of the work involved in fixing the creak, I decided to take care of that at the same time. I’ll also cover that procedure, so you can just tackle that portion if that’s all you’re interested in.
This particular job isn’t all that difficult, but access is a challenge. There were some choice curse words directed toward some clutch components during this procedure! You have to contort yourself into the footwell while looking up into the dashboard – not easy to do! There were many times when I couldn’t see what I was doing and work at the same time. So I had to take a good look, and then work by feel. If you have access to a lift, it may help.
http://www.creative-pro.net/bmw_diy/MasterCylinder.jpg
This is what the master cylinder looks like.
So, first things first: If you have a Bentley manual, leave it on the shelf for this job. The procedure outlined in the manual is not only flat out wrong, but it’s impossible. It must’ve been written for a different model. With the exception of bleeding the system after you’re done, the entire job is performed from within the passenger compartment – not from inside the engine bay as described in the Bentley manual. I also must apologize in advance for the lack of good photos. It was extremely difficult to get photos as I worked. I did the best I could, but it was either too dark, or there were too many obstructions for the camera to focus. Plus, it’s kind of a cheap camera, so that probably didn’t help!
The first thing I would advise would be to pop the hood, and use a suction pump or turkey baster to get as much brake fluid as possible out of the reservoir. Once you disconnect the fluid inlet to the master cylinder, any fluid “above” it in the system will drain out. So the more you remove now, the less you’ll have to clean up later.
Next, remove the lower dash panel on the driver side. It is held on by two screws below the instrument cluster and one along the edge next to the center console. Disconnect the wire for the footwell light and door chime. The edge of the panel near the firewall fits into slots. Make a note of them so you can reinstall it in the proper position.
If you look up into the dashboard, you can see the clutch apparatus. The clutch pedal assembly is a single piece of molded plastic that pivots on a pin about a foot directly above the actual pedal (this is where the creaking comes from). The master cylinder attaches to the pedal about midway up, and the master cylinder is attached to the car with two bolts. The master cylinder attaches to the clutch pedal with a pin and clip. Remove the clip by grabbing the end with needle nose pliers and twisting slightly as you pull. With the clip off, push out the pin. The clutch return spring is attached to the clutch pedal with another pin, but is just seated into a notch at the other end. It will fall out when you pull the pin for the master cylinder. As I took everything apart, I cleaned and greased every moving part.
http://www.creative-pro.net/bmw_diy/OldMaster.jpg
The master cylinder is held in place by two bolts and the inlet and outlet line fittings. Pay attention to the position of all the bits so you can reassemble it later.
To ease access to the master cylinder (and to address the creaky pedal) it’s necessary to remove the pedal assembly. You’ve already done 90% of the work at this point, so you might as well take the extra couple of steps. The assembly is held on the pivot pin by a clip identical to the one for the pin in the master cylinder. Remove it in the same fashion and slide the assembly off the pin.
http://www.creative-pro.net/bmw_diy/RetainingClip.jpg
These clips hold the clutch pedal assembly and master cylinder rod in place. They are easy to remove - once you figure them out.
Thoroughly clean all the nasty dried grease from the pin and bushings and slather on fresh grease. There are two bushings on the pedal. Both of mine had slits in them, but I’m not sure if they are supposed to be there. I didn’t want to wait for new parts if they were, in fact, not supposed to have slits. So I just reassembled it using the old parts. It would probably be a good idea to order new bushings and have them on hand when you do the job. I used a white lithium grease because I didn’t want to take a chance of the grease attacking the plastic bushing or pedal assembly. I’m not saying that’s only product to use, but it seemed like the best choice for me. Set the cleaned and greased pedal assembly aside.
http://www.creative-pro.net/bmw_diy/ClutchPivot.jpg
This is where the clutch pedal pivots (and creaks). Clean thoroughly and grease before you put it back together.
Next remove the two bolts securing the cylinder. The lower bolt threads into a nut, while the upper bolt threads into the bracket that hold the brake and clutch pedal switches. Pay attention to the orientation of the bracket or you’ll tear your hair out trying to figure out how it goes back in (ask me how I know!).
http://www.creative-pro.net/bmw_diy/OldMaster.jpg
This is the same photo as above, but I wanted to show the mounting bolts again.
Now it’s time to get dirty. Place a disposable plastic bowl under the master cylinder to catch the brake fluid that drains out, and put several layers of paper in the floorboard to catch any fluid that spills out of the dish. Keep some paper towels on hand as well. If your fluid hasn’t been flushed in a while and it gets on the carpet, it will stain it (again, ask me how I know).
The two fluid lines are held in place by small metal clips. There are very easy to remove and install. When you are holding the cylinder in your hand. Up under the dash with limited access, it’s a different story. So it’s a good idea to practice a few times with the new cylinder to see how the clips work and the best way to release them. There is a flat spot where a flat-blade screwdriver can easily slip under the clip. But it’s not easy to access on the installed part. So some practice will definitely help. When you’re ready, release the clip for the outlet line first (bottom fitting). Try to let as much fluid as possible drain out. When it’s finished draining, twist the cylinder around to gain access to the clip for the inlet line and release it. More fluid will drain out and run down your arm. Why does brake fluid feel hot when it touches your skin? These parts are plastic, so use care when handling them.
http://www.creative-pro.net/bmw_diy/ClipRelease.jpg
These little metal clips hold the inlet and outlet lines in place. They are easy to remove once you learn how to release them - but it's not obvious with your head twisted around under the dash - so practice on the new one first.
Once the old cylinder is out, install the new one in reverse order. If you paid attention to the various bolt and bracket locations, reassembly shouldn’t present too much of a challenge – except for the return spring. The top end must be properly seated in its notch and it’s tough to compress the spring by hand and force it into place. But it can be done with a little determination and patience. Remember to grease everything that moves!
http://www.creative-pro.net/bmw_diy/ReturnSpring.jpg
I couldn't get a photo of the upper perch for the clutch return spring, so my illustration will have to suffice. The red portion is the end of the return spring and the gray portion is the metal bracket into which it fits. The lower end of the spring attaches to the clutch pedal with a pin and clip, but he upper end just sits in this perch. The spring must be compressed by hand and put in place after the clutch pedal and master cylinder are in place. It takes some force and cussing, but can be done.
Once the cylinder is installed, it’s time to refill and bleed the system. If you don’t have a pressure bleeder, I highly recommend adding one to your parts order. It’s well worth the $55 asking price. Since you drained most (if not all) of the fluid from the reservoir, you must bleed the brakes as well as the clutch. I’ll give a quick rundown of the brake bleeding procedure, but won’t go into a lot of detail since there’s plenty of info out there about it already. Start by attaching your pressure bleeder to the reservoir and filling the bleeder with your favorite DOT 4 brake fluid (I like Valvoline SYN Power). Pump up the pressure bleeder to 20 PSI and remove the right rear wheel. Open the bleeder valve until clear, bubble-free fluid flows out. Next is the left rear, then right front, pumping up the bleeder in between each. The left front is last, but leave the wheel off after you finish bleeding. The last thing to bleed is the clutch, and you can’t get to the bleeder with the wheel on (unless you are using a lift – then it won’t matter). The slave cylinder has the bleeder valve on it, and it’s just like the bleeder for the brakes. Crack it open with a 7mm wrench and wait for the bubbles and old fluid to drain out. If you aren’t using a pressure bleeder, have a helper CAREFULLY press the clutch while you open the bleeder. With the pedal on the floor, close the bleeder, then release the pedal. Repeat until there are no more bubbles. To thoroughly bleed the clutch when not using a pressure bleeder, it’s best to remove the slave from the transmission and rotate it until the bleeder if pointing up. Then bleed it again – this ensures that no air remains in the lines. But BE CAREFUL – DO NOT press the clutch without pressure on the end of the plunger. Hold it in your hands and keep the plunger pressed in. If you don’t, the internal piston will pop out and you’ll have to replace the slave cylinder. This is why it’s highly recommended to use a pressure bleeder! When satisfied that all air is out of the system, reinstall the slave cylinder and put the wheel back on.
Put the cap back on the reservoir and you’re done. Now go wash the brake fluid out of your hair and have a cold one. You’ve earned it! :alright