I just want to cmment on a subject I have thankfully not seen mentioned here in quite a while.

I remember last summer there was a rash of failed harmonic balancers on these forums. I now think I know what led to them.

I am now going back together with my daughter's engine and put on the balancer yesterday. There are two pins that key the balancer to the crankshaft. It is a challenge to get these notches to line up properly so that the buttons can go in place. I began by lining up the balancer with pins and drawing the balancer slowly onto the shaft. I backed off the bolt several times to see where it was. I can see where someone might just force everything together with these two parts not quite lining up properly. I finally began drawing the balancer on without the pins until I could get it in place so that the pins would then fit in place. I probably put the balancer on took it off with a puller ten times to get it lined up. I think this was worth the time to prevent the catastrophe of a failed balancer. I can see how if you messed up the balancer, you could easily be in a situation where you would have to change the crankshaft.

If there are any tricks that I'm not aware of in installing the balancer, I would love to hear them.

Have a great day,

How bout some photos Larry?

__________________
Jim

I've run into the same difficulty lining up the two dowel pins. Try it on a 113 SL; what a pain. The problem is caused by the fact that the balancer turns very slightly as you draw it into position. The last time I did this on my 240D I purposely set it out of line and drew it into place, partially pulled it and drew it back in several times. Slowly but surely it lined up. I'd sure like to hear from the experts if they have a trick for this.

I just replaced the front crankshaft seal on my 1977 300D with engine in the car and had the same problem with aligning the dowel pin hole notches on the harmonic balancer to the holes/notches in the crankshaft. After 3-4 hours of trying to align the holes (probably 20 attempts) and having the balancer twist slightly both when tightening the balancer/crankshaft bolt and also when pulling the balancer off with a puller I created the following alignment procedure:

lightly greased the harmonic balancer and crankshaft contact area (done before the first try to ease installation)

lined up the dowel pin hole notches as close as possible (using a mirror since I could not view the holes/notches straight on because of the AC condensor)

used the harmonic balancer/cranshaft bolt to press the balancer on till the dowel pin hole notches on the balancer overlapped about 1/2 distance length-wise with the notches in the crankshaft (balancer about 2/3 to 3/4 of the way on the crankshaft)

used a brass drift and hammer to tap the balancer in the direction needed to align the dowel pin hole notches (you can also use a pad and a non-brass drift - with the pad on the balancer to cushion and protect it when tapping the balancer into alignment with the crankshaft, or a piece of solid wood in place of a drift with a soft headed hammer or a sand filled plastic hammer instead of a metal headed hammer), place the brass drift onto a place on the balancer that will provide a good contact area so the drift will not slide off easily (the cutouts in the balancer to allow the special puller tool enough room to remove the lower pin that positions the bottom of the timing chain tensioner rail worked well); I had to overcome my relunctance to strike the balancer to align the dowel pin hole notches in place of the procedure the MB and Haynes shop manuals use, but did so because I did not see any other way to align the dowel pin hole notches that kept moving when I pressed the balancer onto the crankshaft using the balancer/crankshaft bolt and then when using a puller to remove the balancer - much less the fact that the dowel pin hole notches are not full length which would help with alignment (seems a straight woodruff key in the crankshaft and full length slot in the balancer would be the best way (as I have seen on all other engines that I have worked on - lawn mower, motorcycle, Chevy, Ford, Dodge, International Harvester, John Deere, etc., etc.), but MB uses their own method and we have to deal with it

used an 8mm drill bit shank (not the drilling/cutting end) to check when the balancer and crankshaft dowel pin hole notches were in alignment (insert the shank into the holes/notches until the maximum amount of play is found - the dowel pin measures 8.3mm so you want the maximum amount of play when the drill bit shank is inserted into the dowel pin hole notch) tap the balancer in the direction needed until aligned with the crankshaft dowel pin hole notches (a light coating of grease or oil helps to ease movement of the balancer on the crankshaft), a 19/64" or possibly a 5/16" drill bit can be used if you do not own an 8mm drill bit or cannot find one (you want something that is slightly smaller in diameter than the dowel pin so it can be inserted into the dowel pin hole notch to indicate which direction the balancer needs to go, but not too much smaller in diameter), although I used a mirror to help with aligning the dowel pin hole notches it has been more than a few years since I used mirrors when doing repairs and it was far easier to use the 8mm drill bit shank to align the dowel pin hole notches (and probably much better than using just your eyes to see if the holes are properly aligned because the drill bit provides a positive measure of alignment)

once the dowel pins hole notches were perfectly aligned (or as close as possible) I put a bit of oil on the dowel pin and then drove it into place using a brass drift checking the fit/alignment very carefully after every tap with the hammer (I replaced the original dowel pin with the new type MB dowel pin which eases installation because it has a longer tapered shoulder than the original; and you can use a non-brass drift if you are carefull because if the alignment is not close to perfect a non-brass drift will ruin the dowel pin - much less avoiding the chance of damaging the balancer and/or the crankshaft, which is why you want a near perfect alignment to begin with), the new type MB dowel pin with the longer tapered shoulder will finish the alignment of the balancer to the crankshaft (however, you want as close to perfect alignment as you can get before attempting to install the dowel pins), then I used one of the old original dowel pins in the other hole to see if my alignment was good (it was, the original dowel pin went in very easily - as did the replacement dowel pin) - I am sure that my harmonic balancer to cranshaft alignment is perfect, but if it is not then I am probably within a fraction of 1 degree of perfect alignment

then I used the balancer/crankshaft bolt to finish installing the balancer all the way onto the crankshaft and then torqued the bolt to over 200 ft. lbs. (spec is 199-250 for a 1977 300D)

One comment, you are supposed to replace the front crank seal spacer when R&R'ing the front crankshaft seal - I could not because I did not have the MB special puller (I own a lot of pullers and none would fit into the narrow opening, much less get a grip on the small area the front crank seal spacer has). I inspected my front crank seal spacer with a powerfull light (using a mirror to inspect the bottom) and did not find any imperfections/wear that could damage the new crank seal. However, only time will tell if I made a mistake in not replacing the front crank seal spacer (no problems with over 500 miles on the new seal - which is not much considering the life span of a seal). I also liberally coated the crankshaft seal's lip with oil soluble grease to ensure it was well lubricated until oil pressure could take over lubricating the seal.

Hope my procedure helps!!
Tom

Mount the three cup springs (washers) with the crown (raised dome) toward bolt head.

The harmonic balancer is secured to the crankshaft by a single 18mm X 45 mm bolt torqued to 270 - 330 Nm = 200-244 ft. lbs.