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I just changed the oil pressure sensor / switch located on the back side of my block. (2.3T B235R, 4 cylinder). It is quite common that this sensor leaks and it's a cheap part ($20). Mine started leaking at 134K miles. At first I thought my A/C compressor was leaking, because the oil spot on the driveway shows up just below the A/C compressor, but not so, it was this sensor. Below is a photo of what the old sensor looks like, covered in oil. I first removed my Starter, which is really easy. The starter is tiny & lightweight, kind of fits in the palm of your hand and comes out easily through the bottom. The top bolt that holds the starter on is kind of buried, so you'll have to feel around blind to find the bolt from the top. I had my car on jack stands and was still able to remove the starter top bolt from the top. I used the Hayes manual for instructions as to removing the starter. I removed the intake manifold, "stay" rod, only two bolts. A little oil will drain out of the hole when the old sensor is removed, but it's not a big deal.



Below is what the new sensor / switch looks like, notice the large crush washer near the threads, it's an odd, "U" shaped washer. Don't worry if your wrench hits the black plastic cap and it moves or pops off, just push it back on, it's not designed to be a seal, just a protective cap to protect the electrical contact:



Here's the critical bit of information that I couldn't find anywhere in any tutorial, online or otherwise. If I were to do this job again, I would not proceed without having this wrench, it's a 15/16, offset box end wrench that has been cut down with a 3" handle. Fits the oil pressure sensor perfectly:



I was lucky when I did this job because I was using a 24mm full size open end wrench to try to tighten down the oil pressure sensor, (tight enough to seal the crush washer) and it wasn't working, the space is too tight for a full size wrench and an open end wrench slips off the bolt head. Fortunately, my friend stopped by, happened to have the 15/16 box end wrench and offered to cut it down, I lucked out. You need to apply quite a bit of torque to the sensor bolt to actually seal the crush washer.



The final image shows the new sensor installed. Now I'm all sealed up again and no more annoying oil leaks. Plus, since I had to remove the original starter, I decided to swap in a rebuilt Bosch starter, (only $85), even though you almost never hear of Saab starters failing. My rule of thumb is that if I can get to a part in the process of getting to something else, and if that part can be swapped with a new or rebuilt, I just swap it out, broken or not. In this case, I was blown away with the new starter, it spins much, much faster the old starter with 134K miles on it.

I hope this info helps someone out there. I wish I had this info, especially about the wrench prior to doing this job, it would have made for a much easier job.
 

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Discussion Starter #3
Always interesting to hear how other owners are dealing with replacing this sensor. It's a cramped, tight space to get to. I've read that some can replace the sensor from the top, without removing the starter, but I don't see how that can be done with an average sized arm.
 

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From the top for me and my longer skinny arms. Just have to unbolt a wiring loom hold down and disconnect the battery. I slit a closed end box wrench too. :)
 

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Discussion Starter #9
From the top for me and my longer skinny arms. Just have to unbolt a wiring loom hold down and disconnect the battery. I slit a closed end box wrench too. :)
Did you use a straight, cut down box end or an offset cut down box end? I wanted to do this job from the top at first, but secretly, I wanted to swap my starter with a rebuilt..
 

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I did this job over the weekend-I hope one of the admins will make a sticky of it and title it "Starter removal and oil sensor replacement".

photousa has done a fab job of capturing most of the work involved.

First image-this shows the starter with nuts removed from electrical connections-both 12mm.

I couldn't photograph it but the lower nut holding the starter in place is 16mm-fairly easy to reach from below.



The upper one is 18mm-It is not to difficult to access-but get ready for some chafing. See the arrow...

To 'break' the bolt I placed a 3 foot pool on my ratcher and it gave easy.

 

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I used a half-inch drive deep wall socket, 15/16. There is enough room in the socket for the wire. put a short extension on it and away you go. no cutting, no rotozip, nothing special. I verified that the new sensor will fit into my socket before I crawled under the car and it fit perfectly!

Edit: Took a photo of the old switch next to a deep wall socket to show how I coiled up the wire.
 

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Second the crowfoot wrench with a 6 inch extension on a rachet. My set only had a 22 MM and I actually needed a 21 MM for my new sending unit, but it never slipped and I was able to do it fairly easily after the starter was out of the way.

Also, none of the instructions I read online mentioned that you have to access the top starter bolt from above. I almost pulled my hair out trying to blindly get a socket on the upper bolt from below, until I got irked and went up top and realized it was buried below a bunch of wiring looms and had to be accessed from above.

Good luck.
 

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Noticed an oil leak that originates from around the starter area and in between the engine and transmission on the back side of the transmission. The oil makes it all the way back to the power steering rack. Everything points to the Oil Sensor. It is still the original sensor with 186,000 miles. Any other areas of concern? The leak started in the summer . I used ATP 205 and it stops for awhile but it comes back. After today's inspection, I doubt that the Rear Main Seal is leaking. If the main was the problem, I assume the oil would have covered the entire transmission housing.

What is the consensus? Is it easier to remove from the top or from the bottom? Does anyone have a nice write-up on how to get the job done? How long does it take?
Thanks
 

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Found a write up by Ohioan. It appears lots of work. Any shortcuts?


"From top of engine,

1. Disconnect negative battery terminal.
2. Disconnect and set aside air duct / intake tube.
3. Between the throttle body and brake master cylinder there's some rigid vacuum lines. They're in the way, and you don't want to accidentally break them. Instead of removing them, simply disconnect them in a couple locations. This allows them to move freely, thus reducing the chance of them breaking when performing the next step.
4. Remove top starter mounting bolt. To find the bolt, just follow the top radiator hose to where it ends. It is a few inches below. Use a long ratchet with ½ inch drive.

From under the car,

5. Remove bracket between block and intake manifold. There are two bolts. It's simple to remove.
6. There's a plastic cable tie around the starter. Cut this off using a pair of diagonal cutters.
7. On starter solenoid, remove small nut for the small, ignition wire. You'll have to do this by feel. Remove wire's ring terminal from threaded stud after removing nut.
8. On starter solenoid, remove large nut for the large battery wire. Then remove wire's ring terminal from threaded stud. Note: this was very difficult to do on my car. There just wasn't enough slack in the wire to get the ring terminal off the stud! :x I eventually resorted to using a long screwdriver to pry the ring terminal off the threaded stud.
9. Looking up at the starter solenoid, you'll see another nut on a threaded stud. This is for a short wire between the solenoid and starter. You do not have to remove this nut. But if you do remove it, it's not a big deal: simply reinstall the nut after you remove the starter.
10. Remove starter's lower mounting nut.
11. Remove starter.
12. Cut wire to pressure sensor. Cut the wire very close to the sensor.
13. Use 24 mm socket and ratchet to remove sensor.
14. Unplug connector. Note: I've read a lot of people had trouble doing this. It only took me a few seconds to remove it. Using a very small, flat blade screwdriver, I inserted the screwdriver's blade between the connector's black housing and the red tab, and then pushed & twisted the screwdriver. The red tab popped right up. I had to do this with one hand, but it wasn't difficult at all.
15. Install new sensor. Since my sensor had a 24 mm nut, I was able to shove the connector and wire into a 24 mm deep-well socket (with ½ inch drive) and use a ratchet. Simple.
16. Mate the two connectors, then push down on the red tab to lock them together.
17. Put starter back in. Make sure starter is seated very well.
18. Hand-tighten the starter's lower mounting nut.

From top of engine,

19. Reinstall and tighten top starter mounting bolt.

From under the car,

20. Tighten starter's lower mounting nut.
21. Reinstall wires' ring terminals on threaded studs on starter solenoid. Again, it was a real pain in the butt to get the ring terminal for the battery wire back on the stud. I eventually got it on, but it took a long time and required a lot of cussing. :(
22. Reinstall bracket between block and intake manifold.

From top of engine,

23. Reinstall air duct / intake tube.
24. Reconnect negative battery terminal."
 

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That write-up looks very thorough. It outlines every single part of every step, which makes it all look more daunting that it is. Half of those steps could be condensed into "remove starter" and "reinstall starter", which is probably what the Hanyes book would reduce it to. :) Having an assortment on tools on hand can make the job much easier. The upper starter bolt is the one I had the most trouble with, because as was mentioned before, it's buried underneath a lot of stuff. There also isn't much room to swing a breaker bar, and it's too tight at first for a ratchet. I ended up using a 12-point socket and a short 12" breaker bar. The 12-point socket gave me more freedom in how the breaker bar was positioned, and the shorter one was small enough to fit in the tight space. I did struggle with getting the new oil pressure switch's plug connected with one hand, too, but it did eventually go together.
 

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"I did struggle with getting the new oil pressure switch's plug connected with one hand, too,"

the hardest part of the job!
 

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I've seriously thought about using a NG900-style oil pressure switch the next time I replace mine, since it uses a simple push-on crimp fitting. I think the switch itself is exactly the same, other than the connector.
 

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It's also a lot easier to get the heavy wire on the starter if you take the wire off of the alternator, that gives you a lot more freedom to move the wire around. Then put the alternator back. Same wrench BTW.
 

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It's also a lot easier to get the heavy wire on the starter if you take the wire off of the alternator, that gives you a lot more freedom to move the wire around. Then put the alternator back. Same wrench BTW.
Just be careful. I tried that trick on my NG900 when the starter died. Wound up pulling the positive stud out of the alternator. The car did not ever run again under its own power, and was eventually dragged away for scrap.
 
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