Otto Mechanic

Hi, I'm doing a clutch job on a '90 S2 using the WSM, which talks about removing the speed and reference sensors from the clutch housing and disconnecting a ground strap conecting the clutch housing to the body. There's a photo of the parts that need to be disconnected and removed in the WSM.

I can't find these parts on the S2 and wonder if the manual pre-dates the S2? Can anyone tell me if these sensors and the ground strap exist on an S2, and if so, where they might be?

Thanks,

Otto.

944hal

Look down the back of the engine to the bell housing, near the firewall. The reference sensor is on top of the bell housing just to the driver's side. It should have a single wire coming from it. The bracket needs to be taken off before the bell will separate from the back of the engine. Not sure about the ground strap. There are two ground wires fastened to the rear of the block on the driver's side. I don't remember taking off a ground strap on the clutch housing, but that's not to say I didn't. I wouldn't worry about it, once you get in there, if it there, you'll find it.

944hal

Update. I just looked at my S2. There are two ground wires just above the reference sensor. One attaches to the bell housing and the other goes on the block. Sorry, I just didn't remember them that way. The ground wires and reference sensor are accessible from the engine bay.

Otto Mechanic

Thanks very much, I've been looking for them from under the car, I have it up on a lift.

I'll drop it and look for them from the top!

Thanks again.

Otto Mechanic

Found at least one of the 2 sensors and the ground strap thanks to Hal's direction, but came up against a really weird problem; there's only one, I think it's the reference sensor, the speed sensor seems to be missing completely? See attached photo, The yellow arrow points at the hole the sensor came out of, in the WSM the photo leads me to think it's the reference sensor. The red arrow points at the hole that had nothing in it, I think it's the speed sensor.

My understanding is that this car just won't run at all if either of these sensors isn't working, one is giving the DME a #1TDC timing mark, the other is giving it RPMs, a failure of either should shut down the engine?

I can't even find a cable for the lower sensor, and the manual talks about a "holder", which also seems to be missing.

Any ideas about what could have been done to this car?

veleno

I think there is only 1 sensor cable on the S2 models vs. 2 that came on my '88 NA. I'll be able to verify this Sunday as I plan to do some work on the car then and can check for you if it's not too late...

Dutch944

I can verify this for sure:

The S2 only has one sensor as it has a different flywheel.

The S2 flywheel has a 60/2 toothing vs the 133 starterwheel of the N/A and turbo with the TDC on the flywheel.

So the S2 has 1 sensor and the N/A and turbo have 2 sensors.

944hal

+1 on the replies. The S2 only has one reference sensor.

Note. There is a gap requirement when putting the sensor back in. You do not want it to touch the flywheel. Check your manual. The bracket allows for the adjustment.

Otto Mechanic

Thanks for the confirmation, I was pretty surprised by the "missing" sensor and cable

Dimi 944

+2

Otto Mechanic

I'm thinking of "notching" the clutch housing so I can gap the sensor before I put it back it. What's the best tool for the job? I was thinking I might use an angle grinder with a metal cutting abrasive blade on it.

944hal

I didn't do this with my S2 but some folks have modified the bracket itself for easy removal of the bell. I gapped mine by using a washer of the correct thickness glued to the old sensor. Once the gap is set and the bracket tightened, I pulled out the old sensor and put in the new one. Might not be a bad idea to replace the reference sensor anyway. The plastic plug on the end gets brittle and cracks over time. I don't recall the part number, but a BMW sensor works well as a replacement and costs much less than the Porsche equivalent. The cable is a little longer, that's all

Dimi 944

Good idea. You can use an angle grinder, hack saw or oscillating tool....pretty much anything that cuts metal.

Grandpa#3

The link below for Clark's Garage will tell you all about the Speed / Reference Sensors on the Bell Housing. If at all possible try to remove the sensor by pulling up and turning at the same time.. If you can remove the sensor you will not have to remove the sensor bracket and thus save the same measurement. Cutting the sensor slot in the Bell Housing is OK IF you plan on going back to replace the Clutch or Rear Main Seal any time soon.

http://www.clarks-garage.com/shop-manual/ign-02.htm

Cheers,
Larry

Otto Mechanic

I've heard of this technique also. Modifying the bracket (holder) may not be the best idea according to Arominus, who has evidence that removing the shield to allow the clutch housing to come off without removing the sensor holder can cause ignition problems; his theory is the tube the sensor (more correctly called the "sender" or "pulse sender") fits into that interferes with the clutch housing is necessary to shield the sender from other magnetic noise and causes startup backfires.

I've discovered my own methods for getting the sender holder out in short order. It took a long time to figure it out, but a reasonably short time to execute. So I haven't made up my mind yet. I may very well be dead before I put another clutch in this car, so spending an afternoon modifying the housing to save 40 minutes when I have to do it 10 years from now could be a false economy

If you're interested in my method, check out the thread "Removing S2 Clutch Housing".