I dropped a nut!
 

Hi guys and gals, this is my first post on the forum and a mishap during the first real work that I have attempted to do on the engine.

I have just replaced the valve stem oil seals in my 1985 300 W123TD-T after reading many how-to's and watching video's online. I remembered to block off the timing chain orifice with a rag but I didn't realize that the camshaft pedestal at the other end had an orifice beneath it. Incredibly, in the last minutes of the job my oily fingers dropped the lock-nut which found it's way into that orifice. Could the nut be stuck somewhere or, hopefully, would it have dropped thru to the upper oil pan where I might be able to reach it after removing the lower oil pan? :embarasse
As an aside, I have read that the crank should always be turned clockwise but I have never been told why. Is it ok or not to turn it back a couple of degrees if one overshoots the timing mark slightly for instance?

that sucks. drop the pan and see if you get lucky but if it's 'stuck somewhere' it won't be for long...

I would first try sticking one of those magnetic retrievers down the hole. You will see if it is open and might get lucky.

Hi nelbur, thanks. I did think of getting a very small neodymium magnet on the end of a piece of bendy wire to try and fish for it but the narrow aperture/slot is directly half an inch below a camshaft pedestal so a regular magnet on a telescoping rod wouldn't be able to fit in the slot so as to be able to plumb the depth. Looks like I'll be dropping the sump when the rain stops.

Yup a strong magnet has saved my ass more times than I'd like to admit.

Well, I dropped the lower oil pan yesterday. Today, Sunday the rain stopped mid afternoon and I went fishing. Using a telescopic antenna type retriever with a magnet on the end I spent an hour or so pushing it in and pulling it out along the upper oil pan chute. There's nowhere near enough room to get an arm in there. I gave up fishing after an hour or so without a catch. The slot under the camshaft rear pedestal is too tight to get anything that doesn't bend more than an inch or so down. I taped a sliver of a magnet to the end of a yard long curtain spring (that I use for clearing out the sunroof and fender drain tubes)which could be manipulated into the slot and down about a foot or so. I fished for about half an hour and couldn't believe my luck when the shiny side of the fallen nut shone back at me from the flashlight. I hooked a length of baling wire and tried to retrieve it but it dropped off, soddit. I swore loud enough to make some passers by look back. Another ten minutes or so and I was ready for the next catch with more baling wire and the antenna magnet. SUCCESS! First thing I did was put the nut in a magnetic tray on the ground and the second thing was to block off the escape slot before screwing the nut on the valve stem top with clean fingers. I will sleep well tonight.

Can someone let me know why the engine should never be turned counter clockwise, even for a couple of degrees or so?

In theory turning the engine in the opposite direction can compress the timing chain tensioner and that decreases the tension on the timing chain leaving the possibility of of the gear coming out of the chain jumping a tooth and ruining the timing.

On the W123 and earlier non turbo Engines it was much easier to compress the tensioner plunger and the Oil pressure when it is running is the main forc keeping the plunger in place.

The Turbo W123 models had a ratchet device that is supposed to make it hard to compress the tensioner plunger but the caution of rotating the engine opposite is still in the manual. I suppose if you suddenly jerked the engine in the opposite rotation it is still possible to compress the tensioner.

On engines beyond the 617.952s I have no idea if their Timing Chain Tensioners have the ratcheting device in them or not.

The Crankshaft Bolt which is what the factor recommends to turn the crank with is the normal righty tighty right hand threads. So turning the engine in the opposite direction on the 617.952s and earlier is the direction that would loosen the bolt if you wanted to remove it. On other Engines I don't know what threads the crank bolts are.

The short story is you can never go wrong only rotating the engine in the direction of rotation.

If you were timing your fuel injection pump and rotated the engine a bit in the opposite direction you would appear to have the right timing but because you slackened the tension on the chain the timing would be off.

Congrats on finding the nut. I know that feeling.

Martin your a lucky son of a gun .Good news at last ..good luck with rest of the job your doing ..