[Zoraster]

Someone please tell me how to bleed this ridiculous thing.

There is a rubber cap that conceals a valve. Do I loosen this? If so, how? I've been loosening the 11mm screw to the right of the rubber cap, which results in fluid, holding clutch down then tightening it. Clutch response is not changing with this method.

[spitpilot]

Originally Posted by Zoraster

Someone please tell me how to bleed this ridiculous thing.

There is a rubber cap that conceals a valve. Do I loosen this? If so, how? I've been loosening the 11mm screw to the right of the rubber cap, which results in fluid, holding clutch down then tightening it. Clutch response is not changing with this method.

The clutch bleeder nipple usually has a rubber "dust" cap on it..which must be removed to get full fluid flow when bleeding. You are doing it correctly..push pedal down while opening bleed nipple, hold pedal on floor close nipple, pull pedal up (sometimes needed if there is lots of air in system). Other way to bleed is with vaccum...I use a "cather irragation syringe"...60cc plastic syringe (no needle, just tapered tip)..push a piece of 3/16 PVC tubin on the tip, and over bleed nipple...with syringe pushed closed...open nipple and pull handle out...close bleed nipple, remove hose, dump fluid...repeat till you get nice clean fluid, with no air bubbles...that will do 90% of the bleeding with only one person..then I give it a few of the "two person pump pedal bleeds" to make sure all the crud/air gets worked outa slave cylinder by making piston in it move during bleeding.

[Zoraster]

Thanks for your response!

Clarify this for me though: The nipple under the dust cap is supposed to be loosened? And fluid is supposed to come out through it? I have not been doing this as the thing seems impossible to move.

[Zoraster]

This is what I'm looking at. I've been opening the screw on the right of the slave cylinder, clutch to floor then closing screw. This is accomplishing nothing.

Losing mind

[The HACK]

http://www.realoem.com/bmw/showparts...08&hg=21&fg=10

See part number 18? Says dust cap? Remove said dust cap. There's a hex nut/bleeder nipple underneath it. Crack open the nipple by turning it with a box or open end wrench, most likely 7 or 8mm (If I recall correctly) counter-clockwise. Opening the "screw" on the right of the slave cylinder does nothing but introduce more air into the system, potentially all the way up to the brake lines.

[dakman]

I bled my clutch when I did the clutch delay valve removal and this guy had great instructions. The bleeder on my e90 was not anywhere near that master cylinder, it is waaaaay under the car almost in the middle. You have to put the car on ramps. You will have to remove a plastic panel, if you find the clutch delay valve, you are close. My panel didn't look exactly like Bill's but close.

I bled mine with the Motive one man brake bleeder. Buy one, it's worth every penny. One word of caution, I actually had to bleed mine twice. Bleed the system, start the car, pump the peddle, bleed just a tiny bit more and then you are done. I bled the system once, cleaned up everything, started the car and found I couldn't get the car in to gear. I went under the car, bled her again just a tiny, tiny bit and then everything was perfect. Except of course I got to clean up all my tools again. PAIN!

Here's link to Bill's site:

http://www.billswebspace.com/BMWCDVMod.htm

And a picture of the bleeder you are looking for. Best of luck.

Derrick

[dakman]

Normally you bleed the system until you don't get any more crap or air bubbles coming out and then you bleed it just a bit more to be sure. Have to say I used almost as much brake fluid bleeding the clutch after the CDV mod as I did bleeding the brakes.

I would have paid Dr. Phuonger in Northern California to do that job if I had known what a pain it was going to be but I'm glad I did it. I installed my short shifter the same day and now my car drives like it should have from BMW.

[bryanbdp]

After a frustrating time with the clutch hydraulic system, I have learned a bit about how it works.

I could not get fluid to bleed through the system, even with 30 psi on the reservoir. Took the slave and the valve at the end of the hose off, still no fluid flow. So, fluid from the reservoir was not passing through the master cylinder to the slave, even under pressure.

Now, I suppose a bad hose is possible, but I didn't think it likely.

When I installed the new master cylinder, fluid immediately started flowing down the hose to the slave cylinder, under gravity alone. Problem found.

I took the master cylinder apart to find out what the problem was. I will try to describe the construction as I didn't take photos.

The master is a pretty simple beast. The shaft is hollow, but solid on the outside end at the clevis, and has a seal assembly at the end of the cylinder to keep fluid from leaking out around the shaft.

At the other end of the cylinder is the output hole, where the fluid goes to operate the slave cylinder. When you push the pedal, a seal on the end of the shaft compresses the fluid in front of it and forces it out the end of the cylinder into the hose.
It's that simple. If there's air in there, you have to force it out.

But here's the kicker, as the clutch wears, the slave has to push a little further, so some additional fluid has to be introduced to the system, or what happens is the clutch slave doesn't push as far as it used to, and the clutch starts to drag, making shifting difficult.

It is this fluid replenishment method that is the problem. Here's how it works:
On the master cylinder shaft is a seal, which compresses the fluid to operate the slave. Behind the seal is just fluid from the reservoir. As the clutch wears, some fluid needs to go from behind the seal to in front of the seal.
This is accomplished with a passage in the hollow shaft and a little rubber check valve at the very end of the piston head. When you push the clutch, the check valve closes firmly and ensures the pressure operates the clutch.
When the pedal returns, if enough wear has occurred, the piston will create a little bit of vacuum on the pressure side, and this relatively low pressure should suck some fluid through the check valve. If pressure is applied to the reservoir, the fluid should be forced through the check valve rather smartly, flushing any air away. Pumping the pedal probably just agitates the fluid and air, making it harder to get the air out quickly.

What I believe is happening, is that the tiny little rubber check valve swells with age, and the clearances are so tight, that the valve seals up and doesn't work anymore. So fluid can not replenish the system, and the pedal gets lower and lower as the clutch wears. Bleeding gets more and more difficult until it's impossible, as in my case. Our car is a 2007, not that old, but old enough, apparently.

Long story short, if you're having trouble bleeding, buy a new master and bleed the system.

The slave cylinder is an even simpler beast, it has a piston which forces out the rod when pressure is applied. End of story. With good fluid flow, it should bleed pretty easily. If unbolted, you can hold the cylinder with the bleeder upwards, open the bleeder, and fluid should bleed out all by itself. If it doesn't, there is some degree of restriction in the check valve in the master, or just dirt gumming up one of the orifices, which are very small. If it isn't leaking, or clogged with gunk, there's probably nothing wrong with it.

Once fluid flows cleanly out of the bleeder, you can press in the shaft a few times to see if any air comes out. Do not depress the clutch pedal until the slave is reinstalled, or unless you have the holding tool, or the slave will blow itself apart due to over travel.

My pedal was rock hard after bleeding, and it shifts like a dream again.
I bought ATE brand parts from eeuroparts.com, cheap money, and I believe they are OEM brand parts.

I had a hard time getting the slave cylinder to go in enough the start the nuts. So what i did was force the rod all the way in until it snapped into its shipping position. After installation, operating the clutch pops the rod free, and does so fast enough that it must engage the dimple in the clutch fork without problem. Worked for me, anyways.

Hope this helps someone, I find understanding a system helps to troubleshoot it, and this is a pretty simple system.

Thanks,
Bryanbdp

2007 E93

[austin.tillison]

Great description Bryan, thank you!

[Tambohamilton]

Thanks for the description, bryanbdp. I was able to remove my MC, disassemble it, 'adjust' (with a countersink bit) the valve very carefully, and reassemble. It's not perfect, since it wouldn't draw fluid through under gravity alone, but it was enough to get me back up and running. I'll see if it deteriorates, or stays functional.

[PCA335xi]

Sorry to revive an old thread but there is surprisingly not a lot of traction on the actual resolution. You can definitely bleed the slave cylinder with a manual bleed or pressure bleeder.

After 2 hours of bleeding today we figured out that only the very top right of the master cylinder is the slave cylinder reservoir.

**It holds practically NOTHING.**

We had to refill the entire master cylinder after each bleed to be sure we didn't run it dry again. We did it manually then, once we figured this out about the slave cylinder reservoir, followed it up with a power bleeder to make sure all the air was out.

ALSO

I have a 335XI and the first bleed I removed the front driveshaft in order to access the slave bleeder, this made it a LOT easier and was not terribly difficult, HOWEVER, I learned later I could have bled it without removing the front driveshaft by using a **1/4" 11mm deep socket and a wobble extension**. The 3/8" wobble extension and 11mm socket were a tad too long and bulky to fully get on the bleeder.

Just my 2 cents.

[Tambohamilton]

What's this about filling the MC, and a SC reservoir? In the clutch circuit there is a reservoir, a MC and a SC... I assume you must be getting your terms confused.

[charlie_m]

Just to clarify, with a manual transmission, the clutch hydraulics share the same fluid and reservoir as the brake hydraulics. Reservoir is separate from both master cylinders.

What PCA335xi is saying is that the fluid level must be very high, almost to the top of the reservoir, to make it into the *clutch* hydraulic side. If you just glance at the reservoir, it looks like there's plenty of fluid, but you just keep pumping air until you add fluid to get it high enough to get into the clutch side. The amount of fluid for the clutch side is very small also, as he mentioned. This is kind of a gotcha when bleeding by hand. And also the reason that the clutch should be included when doing a brake fluid flush.

This is intentional by BMW, so that leaking or damaged clutch hydraulics won't cause a brake fluid loss. Having brakes without a clutch is a manageable situation, but having a clutch without brakes, not so much

[Captain Buumer]

Ah well, i just pushed fluid with syrenge from gearbox nipple.

There was a video showing how clutch cyilinder works and this gave idea to try this way.

Had completely empty system (no pedal pumping at all).
Maybe helpful to someone that one day reads forums in frustration of what to do when no powerbleeder type tools nearby.

[PCA335xi]

Originally Posted by charlie_m

Just to clarify, with a manual transmission, the clutch hydraulics share the same fluid and reservoir as the brake hydraulics. Reservoir is separate from both master cylinders.

What PCA335xi is saying is that the fluid level must be very high, almost to the top of the reservoir, to make it into the *clutch* hydraulic side. If you just glance at the reservoir, it looks like there's plenty of fluid, but you just keep pumping air until you add fluid to get it high enough to get into the clutch side. The amount of fluid for the clutch side is very small also, as he mentioned. This is kind of a gotcha when bleeding by hand. And also the reason that the clutch should be included when doing a brake fluid flush.

This is intentional by BMW, so that leaking or damaged clutch hydraulics won't cause a brake fluid loss. Having brakes without a clutch is a manageable situation, but having a clutch without brakes, not so much

Thanks for clarifying something I feel didn't really need to be clarified

They could have at least let the fluid in the reservoir continue to fill the slave/clutch reservoir until it got to the 'low' marker. The fluid seems to stop transferring over once the level in the main reservoir hits 'high', which is very misleading...

[Tambohamilton]

[Leanped]

I think I might have some more useful information. I tried the classic 2-man pump and bleed method, pressure bleeding backward from the slave, and vacuum bleeding from the slave for a combined total of about 5 hours. I was able to get a partial pedal but it would still get stuck on the way up.

Here's the trick we used to fix it: tilt the car.

Raise the back end up as high as you can get it. I'm talking like 18-24 inches. Then we did vacuum bleeding and got the pedal back within about 5 minutes. I think the position is what mattered the most, so you can try the classic method or the Motive, not sure if they'll work, though.

I think it's something to do with the angle that will free a particular air bubble and allow the bleed to finish.

NOTE: Because the reservoir is split between the clutch and brakes transversely (the partition goes perpendicular to the driveshaft, if you get what I mean), when you raise the car up, the clutch portion in the back will drain fast and you won't even notice because the brake part's fluid can't reach high enough anymore to refill. Make sure you are paying close attention and topping it up.

Good luck everyone!

[e90yyc]

Also going to jump in here and share what I learned from bleeding this system. (I don’t think this has been mentioned yet.)

The easiest way by far to overcome the many challenges of this system is to reverse bleed it by connecting a pressure bleeder to the slave cylinder’s bleed nipple and let it rip. Took a mere couple minutes.

[ryan stewart]

Originally Posted by e90yyc

Also going to jump in here and share what I learned from bleeding this system. (I don’t think this has been mentioned yet.)

The easiest way by far to overcome the many challenges of this system is to reverse bleed it by connecting a pressure bleeder to the slave cylinder’s bleed nipple and let it rip. Took a mere couple minutes.

A decent pressure is the endgame to dicking with hydraulic systems. F that pumping and hoping you get the order right BS. Turns clutch/brakes of any vehicle into a dawdle, getting the car off the ground is the hard part.

[e90yyc]

Originally Posted by ryan stewart

A decent pressure is the endgame to dicking with hydraulic systems. F that pumping and hoping you get the order right BS. Turns clutch/brakes of any vehicle into a dawdle, getting the car off the ground is the hard part.

Agree 100%. But in this case, even with a good pressure bleeder, I found it very challenging to bleed the system in the “traditional” method of pressurizing the MC reservoir. Reverse bleeding was the only thing that seemed to work simply and quickly. This, as I’m sure you all know, is because the air in the system wants to rise, so rather than fighting against that, bleeding from the bottom up takes advantage of it.

In my case, the system was dry as a popcorn fart since it was just swapped in, and I hadn’t bench bled anything. So I’m sure it was extra challenging because of that.

[fleetfoot]

After reading various threads for hours, and getting fairly nervous from all the folks who messed up their clutch bleed, mine went off without a hitch. After bleeding my brakes, I continued on and did the clutch as well following this process:

1. Fill brake fluid reservoir to max
   
2. Fill catch can with ~1" of fluid (to prevent air from backflowing)
   
3. Fill pressure bleeder, and pressurize bleeder to 18psi
   
4. Remove transmission belly pan (3 8mm screws in front, 2 in back, and 2 on each side).
   
5. Remove cap from bleeder valve on slave cylinder, attach catch can hose, and loosen it one (maybe 2) full turns with an 11mm box wrench.
   
6. Let fluid drip until you see fresh fluid coming through
   
7. Close bleeder valve. DO NOT apply too much force since it's PLASTIC. Put rubber cap back on.
   
8. Reinstall belly pan and you're done.

A few thoughts:
The fluid flowed right through for me, and I had zero issues with air bubbles. I did check numerous times that the brake fluid and power bleeder reservoirs were full. I also tapped the brake fluid reservoir quite a bit to get air bubbles out.

I didn't have any issues getting to the bleeder valve on the side of the transmission with an 11mm box wrench.

I suspect that pressing the clutch pedal (especially multiple times) just moves too much fluid too fast, and that might be why the reservoir gets drained leading to air bubbles. IMO power bleeding is the simplest and safest approach. I did the whole thing in less than 15 minutes.

My clutch had been feeling a bit "juddery" lately, and after the fluid flush it feels perfect again.

[oVeRdOsE.]

good job, I know many people swear on pressure bleeding, but if you don't have the tools or diy spirit to craft a pressure tool, the classic way just work fine too. I did many bleed on bmw clutch with the 2 person way and the feel is just like OEM at 0km.