Crank Position Sensor breaks

[talbir]

Hi all,

For the second time in 5 months and 600 miles, the Crank position sensor on my 126 300SE busted.

First time it bust, I simply replaced, assuming it was a one-off. This time, I need to establish why it's breaking. At $100+ each, they're not cheap, although they are easy to replace etc. But when it breaks, obviously, you cannot go anywhere as car will not start without it. Sensor always breaks at the tip, the section in the bell housing area.

Now the sensor ALWAYS breaks when giving mild acceleration, whilst cruising along. It never occurs from standing start.

Any ideas on why this is breaking. I have a couple of ideas, namely :

(1) broken pieces from previous sensor(which haven't been removed entirely) are moving around in the bell housing and causing the new one to break. This seems remote, since the sensor tip is a very lightweight object, and all the housing is plastic. But I'm not ruling it out.

(2) Flywheel isn't true - but surely this would mean more serious issues ?


Any ideas/solutions would be much appreciated.

cheers

 

[Orlando 300E]

Hello Talbir, don?t know if this is any help but....

The same thing happened on my Audi quattro. The trigger for the crank sensor was a half-inch pin sticking out at 90 degrees from the flywheel.
The problem was that my pin fell out!
A new pin was glued in at Audi after 2 months head scratching at a dealership garage. This replacement pin fell out after a few weeks, leaving the only option being a replacement flywheel- £500!!! That was just for the part. Oh and the pin apparently only cost 80p (this all happened 10 years ago).
I was less than amused when the car broke down again after another month. The problem this time was the sensor had been damaged -it had a dent in it. Probably from the pin falling out but there was also the possibility of a stone getting into the bell housing.

Could it be something else loose in there -a bolt or spring maybe or even a stone?

Good luck, hope you track down the problem
Orlando