DIY speed sensor adjustment tool

[Dark Skies]

A while back I posted my woes regarding removal of the speed sensor on my 944 automatic. Readers will remember the bloody thing just would not come out.

The other day I found out why I was having so much trouble. As you can see from the pic the flywheel had clouted the sensor, disrupting the signals to the DME (instant loss of sparks at the coil) and bending it out of shape so that removal was impossible unless the mounting bracket was removed.

Hmmm! This occured despite me temporarily gluing the correct 0.8 mm shim on the sensor in order to set the correct position of the bracket. Looking at the reference sensor I note that the round magnetic insert has made an impression in the base of the sensor that is visibly proud. Chances are that using a .8mm washer to space out the sensor may give the DIY mechanic a false sense of security - you're correctly spacing the flat area of the sensor but not the slightly proud area. An expensive oversite.

I've got around this by using an old sensor to create a handy adjusting tool. To reproduce: cut off the plastic body at the rubber o ring. Pull out the magnet and drill a 7 mm hole up through the body and out the top. Get a 75mm long hexagonal headed M8 bolt and screw it into the hole. You could tap it first but I found it was easy enough to self-tap using the bolt - and, in my view, holds the bolt tightly without the need of a retaining nut.

Screw the bolt to the overal length of the original sensor + the required .8mm gap. NOTE!!! I've found that you can easily get away with a gap of .889mm (and possibly .9mm) without any ill-effects. After my recent expensive mishap this tiny addition gave me a little extra peace of mind.

With the tool in place of the sensor adjust the bracket accordingly. I've found that using a multimeter earthed to the engine with a probe on top of the isolated bolt of the tool allows you to place the stop exactly against the ring gear so that it is just touching rather than forced down (with the possibilty of losing some of the specified gap through misalignement of the adjustable bracket).

Hope this is of use to all.

My car fired on the first turn of the key and happily ticked over despite not being fired up for a few months. To my great joy there were no nasty noises

[AFJuvat]

Not a bad idea at all.

Maybe we should set up some sort of archive for "home made tools" and the like?

Moderators, what do you think?

AFJuvat

[Roastin944]

Thats a good idea, i have already made some homemade tools for my car, id like to see some others, i would also like to know how to make one for tensioning my timing belt, im not spending 500 bucks for a tool to tension it or pay someone 500 to do it! Thanks

John

[AFJuvat]

Repeat after me.

"There is no way to accurately or consistantly retension your belts without the tool"

$500 to retension belts? Where do you get your work done, a retension shoulddn't cost more than $85

$350 to replace belts.

AFJuvat

[Dark Skies]

Glad the tool sounds like it could be useful. I've never felt too confident about tackling my belts - Omigawd! What if something were to go horribly wrong? At least with a garage service you have a warranty to fall back on if it gets screwed up.

Having said that ... how does the tool work? I've not seen one. If it's merely a way of ensuring they're set to a certain tension is it possible one of those weighing thingies fishermen use could be adapted somehow?

[Dark Skies]

By the way - I forgot to mention this earlier. If you use a bolt with the grade strength markings stamped on top be sure to file them down so the surface of the bolt is completely flat.

[todwic]

Originally posted by AFJuvat
Not a bad idea at all.

Maybe we should set up some sort of archive for "home made tools" and the like?

Moderators, what do you think?

AFJuvat

I like the idea~tools I've made

Good show, Dark. I too, have had a slice of sensor woe pie. This will be goin in my bag of goodies, thanks for sharing.