S2 and 968 speed reference sensor question

Mark944na86 · 02-27-2010, 06:02 PM

I'm about to do a clutch job, so first order of business is disconnection of the speed reference sensors from the clutch bellhousing.

A 944 is supposed to have 2 separate sensors in a bracket, whereas the 968 only has one sensor.

My 1990 S2 seems to have the 968 set-up (one sensor) rather than the typical 944 set-up (two sensors). Pic below. Can anyone verify? Is this is normal for 1990 S2? (PET seems to be suggesting it should be a 2 sensor set-up.)

Question 1: How does this affect the steps for removal/reinstallation? Does it even still need to be removed to clear the bellhousing for removal?

Question 2: I was intending to "notch" my bellhousing to make removal of the senaors bracket unnecessary in the future if removing the bellhousing. Can/should this still be done with the single sensor set-up?

Thanks for any advice.

bazar01 · bazar01's Garage

The S2 and 968 only has one sensor in the bell housing.
You can just remove the sensor and the sleeve and leave the bracket. Sometimes, the sleeve will be stuck on the sensor bracket, so you have to soak it really good. If the sleeve wont' budge, you have no choice but to unbolt the whole bracket.
If you remove the bracket, you will need to regap the sensor.

Mark944na86 · 02-28-2010, 04:08 AM

Thanks!

Do you know if the bracket have to come off in order for the clutch bellhousing to be removed?

bazar01 · bazar01's Garage

As I've said earlier, if you pull out the sensor and the sleeve, you don't have to remove the bracket. But it's going to be tough due to limited space. The bellhousing will hang up on the sleeve even with the sensor pulled out. It's not very hard to gap the sensor so if the sleeve is stuck, just pull the bracket out.

Item 31 in the diagram is the sleeve:

John_AZ · 02-28-2010, 09:22 AM

In regards to Question 2
" Question 2: I was intending to "notch" my bellhousing to make removal of the senaors bracket unnecessary in the future if removing the bellhousing. Can/should this still be done with the single sensor set-up?"

I am suggesting that it should not be done on the S2 & 968 or any daily driver-DD 924S 944 series or 951. Track cars -----sure.

Previously....
It is a reccommendation that owners who have the the 924S, 944 & 951 cut the bell housing to avoid future difficulties with reference sensors that with age are rotted/frozen or by contamination, welded to the bracket and the difficulty of getting the sensor bracket off if the reference sensor breaks in half when trying to remove.

Porsche began using the sensor bracket "sleeve" to avoid the electronic interference of the use of the turbo starter electronic field when starting. The starters were causing hard starts & detonation without the "sleeve".

As mentioned in the TSB, Porsche did have a notch in some '87 models and went back to the original design with 2 holes for the sensors. In some models they also used 2 holes AND the "sleeve" (my 88 924S).

Porsche upgraded the bell housings to have 2 slots for the reference sensors.

When I changed the clutch on the 88 924S, I left the bell housing intact.

When I changed the clutch on the 87 924S, I cut the notch.
I also got a Bosch re-manufactured turbo starter and installed. I do not find any difference in starting or any detonation before or after cutting the notch. The 87 924S did not come with the "sleeve". Maybe I am fortunate.

I would not cut the notch on another bell housing in the future.

What I would do...
I would not use the hex head pan bolts origninally on the sensor bracket. I would use the same length 13mm head bolt and coat with anti seize. I would use anti-seize on the reference sensor bracket pivot and rub on the reference sensors as well before installation.

GL
John_AZ

porschetub · porschetub's Garage

Hi,not sure about the 968 but if your sensors are stuck firm there is no way the bracket will come out due to a locating dowel in the casting,it simply won't lift upwards

Mark944na86 · 07:53 PM

Thanks all.

The sensor itself lifted out quite easily, looked like it had a bit of (what I'm guessing is) Mobil 1 between it and the sleeve.

The sleeve is still in the bracket. I can't see really how you are supposed to grab it?

Perhaps I'll just take the bracket off, and regap.

It would be nice to regap with the bellhousing still off (hence my thinking about notching the bellhousing.)

Bazar01, that diagram is the one I found in the PET -- but clearly it for a two sensor set-up, which is why I was confused.

John, if I'm reading the TB correctly, it sounds like the aluminium sleeve was introduced to mitigate the interference problem of "notched" (or "slotted") bellhousings? Therefore, that would suggest that notching would be less of a problem (or possibly no problem at all) if the bracket had the sleeve? Or am I misunderstanding something basic here...

In any case, if the intention was to return to the holed design away from the slotted design, it sounds like my bellhousing won't be slotted from the factory.

John_AZ · 03-01-2010, 04:37 AM

Quote:

Originally Posted by Mark944na86

Thanks all.

The sensor itself lifted out quite easily, looked like it had a bit of (what I'm guessing is) Mobil 1 between it and the sleeve.

The sleeve is still in the bracket. I can't see really how you are supposed to grab it?

The sleeve should slide up to the underside of the reference sensor bracket if you use a small pick with a 90 degree end

Perhaps I'll just take the bracket off, and regap.

It would be nice to regap with the bellhousing still off (hence my thinking about notching the bellhousing.)

Bazar01, that diagram is the one I found in the PET -- but clearly it for a two sensor set-up, which is why I was confused.

John, if I'm reading the TB correctly, it sounds like the aluminium sleeve was introduced to mitigate the interference problem of "notched" (or "slotted") bellhousings? Therefore, that would suggest that notching would be less of a problem (or possibly no problem at all) if the bracket had the sleeve? Or am I misunderstanding something basic here...

In any case, if the intention was to return to the holed design away from the slotted design, it sounds like my bellhousing won't be slotted from the factory.

Your car will have the holed design.

The German engineers decided to correct the hard starting and detonation by useing the "sleeve" as well as the sensor bracket material around the sleeve.

Your suggestion that having the sleeve would cause less problems if you cut the notch. I would agree.

But why cut the notch when you have already removed the reference sensor successfully? Why would you even want to create the possibility of other problems? I would still remove the reference (pulse) sensor bracket OEM bolts and use antisieze on new bolts that can be removed with a socket and not a 6mm metric hex. The bracket pivot should get antisieze applied as well.

Reasons to cut the notch.
1. You do not plan to replace the RMS or fear it will leak. Use the Elring seal properly installed.
2. You do not remove the FW to be surfaced.
3. You decide to use a radical clutch disc that is normally used for track cars or go cheap. For OEM performance and smooth shifting go Sachs. I am pleased with an Italian disc I got for $200. A little more bite from dead stop but you get used to it.
4. You do not use new FW bolts.

GL
John_AZ

Mark944na86 · 03-01-2010, 05:02 AM

1. I plan to replace the RMS, and I do fear it will leak. The seal I'm getting is from Paragon (bundled in their "clutch accesories" kit), but the brand of seal wasn't specified, so could be Kaco, VR, or Elring (I should have asked Jason before it was shipped out). My fear of leakage is more related to my personal success rate with oil seals, rather than the brand of the seal though!

2. I am planning to get the FW resurfaced.

3. I did go somewhat cheap on the clutch kit: I opted for the the ****** kit which has a "Power Friction" (Raybestos material) disk, and the Sachs PP and T/O bearing.

4. New FW bolts and PP bolts come in the Paragon "clutch accessories" kit.

So how did I score?

John_AZ · 03-01-2010, 05:21 AM

Excellent!

But....RMS
The preferred seal is the Elring due to the design of the inner lips. $$$
More forgiving.
The least preferred is the Kaco seal (Pelican). I use this seal.

Preparation.
Wipe the crankshaft until it shines.
Do you see any tiny grooves? Use Elring.
Coat with heavy conventional motor oil.

Clean the engine seal area and remove burrs from the "screwdriver-seal removal slot"

Use Curil T on the outter edge of the seal if scared of a leak. If Curil T is not available, I use WD-40 sprayed in the engine seal area and on the outter edge of the seal.

Evenly press the seal in-until it bottoms in the seal cavity. Before you press it in look at the bottom lip. The seal will be deeper than flush with the block-slightly.

I use a 4" PVC screw end cap-cutout the square center piece- to tap in. There is a professional seal installer for USD $150 on Pelican or ZDmack? tools.

Search for other opinions.

GL
John_AZ

Mark944na86 · 03-09-2010, 06:10 PM

Update: For the record, the sensor bracket does _not_ have to be removed for the bellhousing to come off on the S2. All that has to come out is the reference sensor itself, and the aluminium sleeve. (Thanks John for the tip for getting that out -- I used a coathanger wire bent to shape to fish it out.) This is just to confirm exactly what Bazar01 said earlier.

So no need to consider notching the bellhousing one way or the other! Much simpler... thanks all (especially John_AZ) for all the helpful advice.