Step 1. Remove the retaining bolt on top of the sensor-not the locking or pivot bolt.
Step 2. Wiggle the sensor out of the sensor bracket.

http://forums.pelicanparts.com/uploa...1319374702.jpg

Step 3. You are unable to lift the sensor out of the sensor bracket.

A. The reference sensor is corroded to the sensor bracket so severely that you will need to smash the bracket in pieces and buy another.

This is caused by the sensor "O" ring hardening.
This is caused by coolant from the heater control valve leaking on the sensor bracket.
This is caused by climate conditions.

There is no room to get to the sensor locking and pivot bolts especially on the drivers side. You could remove the intake for more room to work.

If you use force to get the sensor out, you will break it in half.

After hours of frustrating, knuckle bleeding agony, you will smash the sensor bracket to remove.

When you put the new sensors in, use anti seize bolt lubricant.

Very common.

GL
John

Mono,
Your 924S chassis is the same as an early 944. The 924S engine is exactly the same as the same model year of 944. The 88's have one extra small hose off the manifold that serves the PCV (positive crankcase ventilation) system.
Use what tools you have, but:
I use a 1/4" drive ratchet with a 12" extention. I use a wand magnet. It's super important that you stuff/cover the sight hole in your clutch bell housing so hardware doesn't fall down there.
You can undo the 10mm (head) bolt that holds the bracket for the sensors. That will give you enough room back there. When you try to get your hand in there, you'll have to push the heater control valve out of the way. If you have to, remove the small hose clamp/water hose that goes to the J-pipe at the rear of your head. This is the return for the heater core. If you do this, you'll need to bleed any air out of the cooling system later- no bigee. With the hardware out, spin the sensor some and get two fingers behind it like you're pulling back a bow(and arrow) string. Sometimes they come out easy, other times hard.
As I said earlier, the sensors are interchangeable, but make sure you get the correct sensor attached to the correct plug on the wiring harness. If you hook up the sensor functioning in the BG position to the plug for DG, then engine won't fire at all.

John,
NO, NO NO! Funny guy. I've been thru that stuff, too. But you can break the engine block as easily as the sensor mounting bracket.

Mono, If the sensor doesn't slide out, squirt some PB Blaster, liquid wrench, etc down there and keep spinning it. Squirt and spin. It will come out.
Also, if you're getting fuel and spark, your ignition switch is good.

YEAH, YEAH, YEAH--

Here are a couple examples:
Long read but entertaining....
http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/457162-my-new-944-reference-sensor-dillema-need-some-advice-porsche-gurus.html

Another more recent-. I put a picture of a bracket I had to saw to get the sensor out:
Need Speed Sensor Bolt - Rennlist Discussion Forums

groaning :)

John

EDIT:

CAUTION---YMMV----Some people may not know how to hold a chisel and hammer.

Remove the bell housing to get the sensor out as a last resort.

Use the chisel on the bracket only----do not chip the block

John

John,
I know, I know.....I hear ya.....
The last one I did took me 45 minutes of spraying and twisting. I even had to use the trick of spraying the PB Blaster , which we at the race shop affectionately refer to as "weasel piss", onto the shaft of a screw driver so that it runs down the shaft and goes exactly where you want it.
Lots of cussing later.......little by little it starting spinning. More weasel wee-wee. Spin it. Started spinning farther. spray it......I was spinning it back and forth before it came up even a millimeter!

There are at least 3 types of sensor brackets that Porsche used to hold the sensors and this was the worst kind- the one with the extra long steel sleeve in the BG position. In the end, we won. Now that particular sensor was smashed, burned, run over, then sent thru a wood chipper. But at least we didn't get angry about it.
BTW, the rennlist thread had a mistake. The 6mm bolts that hold down the sensors are specially shaped for one reason. Not to spread load or limit compression force. The reason they have that thick shoulder (looks like a cylinder spacer) under the head is only to stand the head of the bolt off from the sensor. If you didn't have it, your 10mm socket would contact the sensor before you could get the bolt down tight. The sensor has two "walls" very close to its hole as seen in your great pic above.
Another BTW, I believe, you can use the 6mm bolts from the pivot point of the top half of your back seats. Same shape, just a bit shorter.:)

John_AZ/Timmay! Thanks guys - This is exactly the level of detail I'm looking for - appreciate it. Will come back with an update asap!

Realized I said I have spark at my recap several posts back... I actually have no spark as I also mentioned earlier- Still going in the sensor issue direction.....

What is the torque spec for the retaining bolt?

Reference / speed flywheel sensor mounting bolts. 6mm special bolt. I'll start a new thread to make these pics easier to search for.
Here's some pics of the special bolts for holding down the sensors.
#1 is the correct bolt
#2 is the bolt from the pivot point of the top of the back seats, which is a workable substitute.
#3 is a regular head 6mm bolt.
You can see in the second pic that the head of a normal bolt becomes totally recessed in the sensor and you can't get a socket on the head to tighten it down. This is why you can't use a regular bolt of the same length.

http://forums.pelicanparts.com/uploa...1319488195.jpg

http://forums.pelicanparts.com/uploa...1319488246.jpg

FINALLY!! Success. The reference sensor that tested bad at the connector (no reading at all) was the culprit. I hope the pictures come through that I've linked to - if not I'll try again. It appears the wire insulation had hit its threshold after consistently rubbing up against something for too long and ultimately exposing wire...unfortunately, I couldn't identify what that something was. At first, I though it was burnt but it looks more like wear...different ideas?

This sensor was the one closest to the firewall. The swap was not an easy job IMO due to its location and extremely tight hardware fit...well, at least for a 924S beginner like me. in short notes...with great help on this forum and Clarks Garage...sprayed a little penetration oil (not needed in my case, however...retaining bolt was in great condition upon twist and removal)...thanks to Timmay! for the note on using a 14" 1/4" extension - bought one today and it was a perfect fit for accessing the location...used a Craftsman magnet wand with a light at the end for grabbing the bolt upon removal (light VERY helpful)...definitely needed to push heater valve to the side as noted by Timmay!...did not remove hose attached to head...though this would have made access much better...undid a number of plastic straps holding wiring harnesses to firewall to make more room for my forearm...disconnected a couple connectors to make even more room...undid a 10mm bolt holding a vertical hose fitting over the sensor (sorry, I don't know what the hose is) - this allowed some vertical play so I could wiggle the sensor out...and most unexpectedly, I recalled someone on PP forum mentioning he had to climb on top of the engine to get something done - so, frustrated with my inability to adequately reach the sensor given the confines of the engine area, I threw some towels on the sidewall and climbed up there...this was the only way I could best grab back everything I needed to pull up or pull aside while bow-stringing (reference Timmay!'s earlier post) that sensor out...and bow-stringing really is the best way to describe what needs to be done. many bruises and scrapes later I got the thing out...and quickly covered the hole with piece of an old shirt while I worked to clean up the area and figure out how to better situate all the crud in there that made it so difficult to get to.

reverse all that, I got the new sensor in, reconnected everything, cranked the engine and it started!! awesome.

Test Drive - seemed to idle a little better....drove it for about 10 miles - the engine seemed to run better...certainly seemed faster...especially in lower gears...and even had a slightly different (healthier?) sounding note. Should I replace the speed sensor as well?? would that even make a difference performance-wise?

THANKS to all who have helped out with the diagnosis here. Your input and attention is much appreciated!! It's great to have the Porsche back on the road :)


http://www.flickr.com/photos/4778289...th/6278734579/

Hopefully, this image upload works.

http://forums.pelicanparts.com/uploa...1319523288.jpg

http://forums.pelicanparts.com/uploa...1319523303.jpg

Excellent. :)
Welcome.

yaaaaa!
 

Replaced a sensor ! Now, wasn't THAT fun?

Replace the other one at your discretion and leisure.

Good work Soldier! two smileys and a cool :D:D:cool: for you!

Thanks SolReaver - Yeah, I won't be feeling the urge to do that again anytime soon! Learned a lot of the process, though...