S52/ZF 320 Slave cylinder issues

[johnjohnsons54]

I'm using UUC flywheel and M5 clutch-pressure plate-TB-M3ZF slave. It feels just like the getrag with the m20.
Bleeding was no problem. i pushed the clutch to the floor and left it there and tapped the hose until no more bubbles came up. then pushed it a couple times, left it up and did it again. I repeated this until i couldn't get any more bubbles out. then i went under the car and bled the line and slave with my nephew pumping the pedal. After this the grabbing point was still a little bit low but improved as i was driving the car. after about a week it settled down.

Thanks for the input. Out of curiosity how do you like the UUC clutch/flywheel setup? Sounds like it works perfectly with your ZF transmission? Are you running their lightweight flywheel and if so is it worth the extra $$? Any chatter to speak of? Sorry for all the questions....it's a package I've been considering, (as well as JB Racing) if my current setup turns out to be fvcked

[johnjohnsons54]

I came across a random thread during an internet search where a guy had the same issue with his S50 swap/sachs clutch/zf setup.

He figured out that the e36 325/328 slave is slightly smaller in diameter then the e36 m3 slave (same as e30 getrag slave apparently) and when he used it, the slave pushed more fluid, had more throw and everything worked perfectly from that point on.

You guys think it's worth a shot?

[treff-7]

Thanks for the input. Out of curiosity how do you like the UUC clutch/flywheel setup? Sounds like it works perfectly with your ZF transmission? Are you running their lightweight flywheel and if so is it worth the extra $$? Any chatter to speak of? Sorry for all the questions....it's a package I've been considering, (as well as JB Racing) if my current setup turns out to be fvcked

i love it! i never drove a s/m50/52 engine powered car before so i can't really compare but the way it drives i really like! chatter is not really bad because the clutch has the springs. if the engine is under about 1200 rpm and you push on the accelerator you will hear it because of the LTW flywheel doesn't smooth out the vibration but it's not annoying. most people doesn't even use the engine in that range. when it idles there's no chatter.
clutch grabs where it supposed to, you can't tell that it's not the way it came out the factory. I also use the steel braided clutch line.
I don't think your current setup if f**ked. people made it work before. you just need to figure out what doesn't play nice with it. you might be right about the slave. i have a blurry memory of reading it somewhere that the 325 slave needs to be used with your setup...

[325issguy]

IF i remember correctly, you have to force the clutch through the motions then keep pumping. It takes alot of repetitions... Once you finally get some pressure from bleeding and can actuate the clutch go drive it around and it should self bleed... You may have to repeat the bleed process after the driving.

[cormier]

^^ you're correct. UUC recommends using the 325 slave is using their stg2 flywheel with a zf, in order to retain "stock clutch feel"

[johnjohnsons54]

For anybody who's interested, I seemed to have solved the problem and the clutch now works perfectly and has the proper engagement point. After reinstalling the zf slave I ran into the exact same problems Nick experienced.

I ordered a 325 slave and the corresponding braided clutch line from Rogue engineering. Just for the hell of it we tried using the aforementioned braided 325 line with the e36 M3 slave already in the car and VOILA! Works perfectly and I didn't even need to try the 325 slave. I'm guessing my old clutch line was really crappy and just ballooning under pressure and as a result the slave wasn't getting enough fluid and there wasn't enough throw.

If anybody is interested I have an brand new zf e36 M3 slave for sale as well as the corresponding UUC e36 braided stainless clutch line for sale.

Thanks to everybody for your input. I'm super pleased that this is finally sorted

[nmlss2006]

Bringing this back up. As far as I can tell, I have the M42 master in the car (91 318iS) and a 1995 M3 ZF gearbox with associated 1995 M3 clutch slave. The clutch disengages VERY suddently at a very low pedal angle - that is, a small movement of the pedal will cause it to disengage completely. This is... obnoxious, but the worst part is that the effort required is very very significant and the SO is complaining. From what I read, my best course of action is to purchase:
1) SS clutch line
2) E36 325i/328i slave
and install that setup?

Edit: apparently all E30s have the same master cylinder, so I only need the clutch line and the E36 slave?
Aha, clarity: All E30s and the 325/328 have a D=20,64mm slave cylinder. The E36 M3s have a D=22.20mm slave.
So IOW, switching cylinders brings you back to the E30 (and E24 and E28 ) stock diameters. The interesting thing is, unless they changed physics on me, a reduction in diameter of the slave piston will SHORTEN pedal throw and INCREASE effort, not the opposite. What am I missing?
(Of course, the geometry of the fork and the clamp pressure of the clutch springs will vary between all these cars and that will affect the force that is necessary at the pedal, but I can't see how ceteris paribus going from an E36 M3 slave to an E36 325 slave will make things better?)

[butters]

I have the M42 master in the car (91 318iS) and a 1995 M3 ZF gearbox with associated 1995 M3 clutch slave. The clutch disengages VERY suddently at a very low pedal angle - that is, a small movement of the pedal will cause it to disengage completely. This is... obnoxious, but the worst part is that the effort required is very very significant and the SO is complaining.

I have the same setup in my 318. I hate to be the bearer of bad news, but I would call what you describe perfectly normal. If engagement occurs at a high angle, you have problems and likely need to re-bleed the system.

I put in a UUC clutch line immediately so I can't speak to the net effect of that one part, but theoretically you are tightening up the system which would, again, reduce the required pedal travel for engagement. Think of it this way, if the factory rubber is expanding a bit, you have that extra expansion to compensate for by pushing the pedal farther.

Of course, the geometry of the fork and the clamp pressure of the clutch springs will vary between all these cars and that will affect the force that is necessary at the pedal, but I can't see how ceteris paribus going from an E36 M3 slave to an E36 325 slave will make things better?)

I can't see that either. Easy to try, for science, but I'm with you on the mechanics of why it shouldn't help.

The fork geometry is the same (for the ZF trans) and the only factor that affects how much force the slave needs to exert is the clamp pressure of the clutch (the pressure plate fingers, not anything to do with the clutch's hub being sprung if applicable).

What clutch do you have? The pressure plate is what you need to look at if you really want to change things up. I know that my relatively heavy pedal is a result of the south bend / DXD clutch I used, which features increased clamp load over OEM thanks to the upgraded pressure plate.

If your SO is complaining about a heavy clutch that engages quickly with minimal input, unfortunately the real solution is practice and learning to adapt to a sports-type gear change. Minimal input is a good thing, this is not a Jeep Wrangler, and you want to be engaging the next gear quickly.. well, because sportscar.

[nmlss2006]

I have the same setup in my 318. I hate to be the bearer of bad news, but I would call what you describe perfectly normal. If engagement occurs at a high angle, you have problems and likely need to re-bleed the system.

I put in a UUC clutch line immediately so I can't speak to the net effect of that one part, but theoretically you are tightening up the system which would, again, reduce the required pedal travel for engagement. Think of it this way, if the factory rubber is expanding a bit, you have that extra expansion to compensate for by pushing the pedal farther.

This makes perfect sense and confirms that things will not actually improve if I change the line. If the current line (which BTW has been bought new for the swap, BMW part) were expanding, I'd get the opposite effect to what I am lamenting.

I can't see that either. Easy to try, for science, but I'm with you on the mechanics of why it shouldn't help.

The fork geometry is the same (for the ZF trans) and the only factor that affects how much force the slave needs to exert is the clamp pressure of the clutch (the pressure plate fingers, not anything to do with the clutch's hub being sprung if applicable).

What clutch do you have? The pressure plate is what you need to look at if you really want to change things up. I know that my relatively heavy pedal is a result of the south bend / DXD clutch I used, which features increased clamp load over OEM thanks to the upgraded pressure plate.

Well, unless my mechanic changed things without billing me for them (...), the flywheel/clutch assembly is OE BMW for the US S50, with a new clutch disk, pressure plate and TO bearing.
The thing is, such a setup should not be this heavy (the S50B32 OE setup, which is one of the heaviest OE setups out there from a force-on-pedal standpoint, is not as bad, the S62B50 is positively loose by comparison), nor should the engagement be anywhere near this abrupt. The clutch behaves as if it were one of the old-style metallic racing clutches, which is unusual to say the least.

If your SO is complaining about a heavy clutch that engages quickly with minimal input, unfortunately the real solution is practice and learning to adapt to a sports-type gear change. Minimal input is a good thing, this is not a Jeep Wrangler, and you want to be engaging the next gear quickly.. well, because sportscar.

The problem is, we own other cars, BMW and other brands. We both concur that this clutch is the touchiest by a very great margin AND the SO has meniscus problems which make 'well, just deal with it' a suboptimal answer.
What I'm trying to get to here is that there is no reason for this particular setup to be this difficult. The only thing that comes to mind is when the S62's clutch in the M5 had decided that it had lived a good long life and while the rest of the parts were fine, the pressure plate became unbearably heavy and so did, by consequence, the pedal. The assembly was replaced (pressure plate, clutch disc and TO bearing) and the car went back to how it had been from the factory. But I find this kind of failure mode... unusual, not to mention violently premature considering the parts have been driven less than 2000mi.

So I'm puzzled:
1) by the currently accepted belief that replacing the M3 slave with a 325 slave actually makes the pedal softer
2) by the behaviour of my specific setup, both in force required and in suddenness of engagement, with more emphasis on the latter
3) by the possible failures that I can assume from previous experience - this points to an M5-type failure, which is supposed to be extremely unusual

I'm also more than somewhat annoyed at the prospect of having to replace the clutch etc, given how DELIGHTFUL the process is in swapped cars and given how I'm not entirely keen on having my mechanic do this for a number of reasons. So I was looking for alternatives.

[butters]

How do the E30 and E36 master cylinders compare in diameter?

[nmlss2006]

They're identical, according to BMW spec.