Help please: Removing and installing TDC reference and engine speed sensors-1989 3.2

[89PS911]

My winter maintenance schedule this year includes changing the CHT, TDC and speed sensors on my 1989 3.2 Carrera (77,500 miles; developed a hot restart problem late last autumn; I am replacing all of the sensors given their age and the condition of the rubber covering their wires (all dry and flaking off)). O2 sensor is in; new fuel filter also in.

I have the old CHT sensor out and the new one in at the cylinder head; its wire is ready to be pulled through with those of the TDC and speed sensors once those sensors are in at the engine/transmission side.

I am trying to remove the TDC and engine speed sensors while leaving the bracket for these two sensors in place so I don't have to reset the gap between the speed sensor and the flywheel teeth.

I have the lower (speed) sensor unbolted and backed out of the bracket about 1/2"; so there is still a long way to go before it is out of the bracket. I have backed it out as far as it has come by twisting it and pulling on it with my hands and with long needle nose pliers.

Any ideas on how to encourage this sensor and the TDC sensor to come out without removing the mounting bracket for these two sensors?

Or should I just remove the bracket to make my life easier?

Follow-up question: When I get to the point of putting the new TDC and speed sensors into their mounting bracket, do they typically just slide in easily? I read on another post from 2011 that it is important not to twist these sensors on installation due to the risk of breaking wires internally--is that correct?

Thoughts are welcome!

Thank you.
Jonathan

[Flat6pac]

Take off the unit from the engine, clean it and load the 2 sensor. Epoxy a washer about .8mm to the flywheel sensor. Install and tighten against the flywheel. That will be your .8mm setup
I don't like to do sensors in the car.
Bruce

[89PS911]

Thanks Bruce.

Just to be sure I understand correctly.

Remove the bracket holding the TDC and speed sensors from the engine.

Take the sensors out of the bracket.

Clean the bracket out.

Load new sensors and bolt into bracket with hex head bolts. Epoxy an approximately 0.8 mm washer of smaller diameter than the face of the speed sensor on the face of the speed sensor.

Swivel sensor bracket and tighten it down so that washer on face of the speed sensor is against flywheel teeth.

Unbolt speed sensor and slide it out from the mounted bracket and remove the washer from the face of the speed sensor (what epoxy should I use so that washer removal is not difficult?).

Reinsert speed sensor into bracket and bolt in, leaving 0.8 mm gap between flywheel teeth and face of speed sensor in place of where washer was.

Is this all correct?

Jonathan

[Klax]

You want to epoxy the washer to the old sensor and use that to set the attachment angle of the bracket. Then once you have the angle set or referenced, put the new sensor in.

The old sensors have a tendency to rust themselves to the bracket, mine did, and you might need to buy a new mounting bracket. Since you are only getting half the old sensor out I think you may have this issue.

[89PS911]

Thanks Kevin. My difficulty is that my old sensors are, as you noted, likely coming apart and are rusted into the existing bracket. Given this, I am not likely to have an old sensor to do the gap setting with the washer and with the new bracket (I ordered one from our host so everything is fresh). Perhaps I will be able to work the other sensor out of the old bracket in good enough condition to use it for this purpose. Any other suggestions?

Jonathan

[rwilner]

I'm not familiar with this area of the engine. Is there space for a feeler gauge?

Fwiw, in other applications where I've used hall effect sensors (including an application for a 914 fuel injection system), the specific distance wasn't so critical -- just had to be "close". Probably not a helpful answer but I suspect if you screw it in and then back off 1/4 turn, you're there.