W123 M110 harmonic balancer drama
 

Hi,

I have a 1980 W123 280E with the M110 2.8 litre


I have removed the balancer to change the water pump, now I can see one of the keys on the inside of the balancer has been dislodged, it is the part that fits in the groove on the crank, like a woodruff key but different design, circular shape, there are two of them

How can I repair it or is it now unrepairable?

Would I be able to put the balancer back on with just one key or is that going to be a disaster if it fails?


Thank you

Was your hb wobbly?

If the holes are wallowed out it is unlikely it can be repaired satisfactorily. Folks have tried, mostly unsuccessfully.

Sadly the only other solution is a new crank.

If it came out, just put it back in the groove. If it's missing, you can get one through a Mercedes dealer.

The crux of this is the crank. If the two grooves in it are still in good shape then you really have no problem. The two round pins that serve as the keys are available at any Mercedes dealer.

If the grooves in the crank are messed up you can use a file to clean them up. Lightly now; a little bit of filing here goes a long way. Dressing a piece of metal like this is more of an art than a science.

I am guessing here, but it sounds like the keys were gauled when a previous repair was performed. This is really not uncommon, but you don't know about the gauling until you remove the balancer again.

When I replace the front seal I always replaces these pins with new ones. This is sorta overkill, but they are cheap so why not?

If you think the crank needs dressing I would not do it myself, but would ask my favorite machinist to do it.

These keyways usually are damaged by people installing the hb who don't know what they are doing.

More than likely me lol. I still have the loose pin, but how do I go about putting it back in the balancer? Is it a press fit?

Thanks

The pins are installed as the balancer is pulled on with the large bolt I believe but don't try it unless you have a FSM which explains how to do it.

it's not that hard.
The two pins are Offset,mening that they only go into the crank in one place. Put them in the grooves in the crank,then place the hub on the crank snout so you can see the pins and the grooves in the hub.
You may have to turn it 180 degrees to line it up so don't push it on hard yet.
Once it's lined up,get something to mark the hub and the crank nose.
Take the hub and place it in a hot oven for about 20 minutes. once it's really hot,pick it up with a cloth so you don't get burnt and slip it onto the crank snout.
The hub only needs to go on to the point where the pins are just going into the hub,let it cool off a little so it doesn't cook the seal.
put a blob of grease on the hub.
You then use the crank bolt to pull it home onto the pins.
Loctite make a very good shaft lock fluid to hold the pins tight. You will need the loctite primer to clean the pins and the grooves in the crank to make sure it works . mercedes has been using this stuff for over 40 years on loose crank pulleys so it will work for you too.
i have seen engines where the hub was just bashed on and the bolt used with an impact driver to pull the hub home....and the pins weren't lined up. one was so bad the hub had New holes driven into it .of course the timing marks were miles out.

thank you very much mercmad6.3