In stock form, the E46 BMW with a manual transmission has what’s called a clutch delay valve, which is essentially a step-down fitting in the hydraulic line that slows engagement and disengagement of the clutch.
The valve strikes me as a way to make the car feel more refined or a way to tame the springs of the pressure plate so ham-footed drivers don’t deliver their passengers a jerky ride through abrupt engagement of the clutch, intentional or otherwise.
But if these are enthusiast cars, and the E46 ZHP certainly drives like one, then its drivers should know how to work a clutch pedal properly and the clutch delay valve has no place on such a car. In fact, there’s a string of pages on the Internet dedicated to the debate over the valve and how to get rid of it.
In the last installment of HPDE46, I installed braided stainless brake lines. I also installed a braided clutch line with the intention of removing the clutch delay valve. You can do that if you reuse the OEM hose or replace it with a factory piece, but the line we bought from ECS Tuning has a different-size fitting on the end that connects to the hard line that leads to the slave cylinder.
That’s not a big deal, but it means the new hose won’t sit properly in the grommet and bracket meant to hold the assembly in place. When you run through the photos, you’ll see what I mean.
That meant I had to buy a “clutch unlock valve” from UUC Motorwerks — spelled with an “e,” of course. The UUC valve is the same size as the OEM and it fits into the grommet and bracket. The difference is that the orifice on the inside is larger than the OEM valve. There’s a photo of that, too. Sure, I probably could have drilled out the old valve, but I wouldn’t know what size it should be, and the UUC valve was cheap enough. About $35.
The job isn’t difficult, although BMW doesn’t make the bleeder valve for the slave cylinder easy to get to. There’s a tangle of looped hydraulic lines in the way and the valve fitting is a tiny 7 mm. I’m sure there’s a special tool from the factory for getting at it, essentially a long 7 mm box wrench.
The other end of the hose slips into a fitting on the chassis and is retained with a small clip. Easy on and off. The rub, as it was with the brake hoses, is the uncontrollable dribbling of brake fluid and the order in which you must install the hose. Screw it onto the hard line first, then slip it into the chassis fitting with the spring clip.
The good news is that BMW supplies fluid to the slave cylinder from the brake master cylinder, which we know is a good idea since the same kind of system also was on a Mazda I once owned. What’s more, the supply hose is above the “Minimum” mark on the master cylinder, so no matter how much fluid drains while you’re doing the job, it won’t empty your master cylinder.
The job takes less than two hours and that includes jacking the car up on four stands and taking it down.
So, how did the car feel after the swap? Well, not much different, really. Clutch pedal feel improved, mostly, which was fine with me. With the new valve, I could feel the “tipping point” of the springs in the pressure plate. I liked that. When I first bled the system, the pedal felt spongy, like there was air in the line. Turns out there was because we bled the system with the front of the car higher than the rear. I had raised the front jack stands higher than the rears to provide more room under the car.
That didn’t work because it put the bleeder screw at the lowest point on the slave cylinder. Bleeder valves always need to be at the top of the system so the air can rise to the top. We lowered the front jack stands to level the car and bled it again. That worked.
At first, engagement seemed to occur lower in the pedal travel than it had before, but after the car sat overnight, engagement was back at the top of pedal travel where it was before the swap. And the pedal feel was still much improved.
I’m really starting to like this car, and it’s getting close to being ready for a day of HPDE. You BMW guys might be onto something here.