I found the bolt which holds the harmonic balancer on the garage floor this past wekend. I was backing the car out and heard a strange sound, it was the bolt flying out from under the car. There are three washers along with the bolt. Two of them are flat and the other is a belleville washer. I looked on the service manual CD and it talks about three belleville washers. I am not the original owner of this vehicle. Does anyone have any experience with this set up? It looked like the previous owner had the belleville washer with the "cone" facing the crankshaft. Any advice would gladly be appreciated.

You do not indicate what model MB you are working on.

I will assume that it is a 123 diesel since it is the most common engine to experience this maledy. What I will say probably applies to whatever model.

The most common problem with these harmonic balancers occurs due to ignorance on the part of mechanics that have removed/installed harmonic balancers on other make cars and follow the same procedure on these engines. That procedure potential can destroy a crankshaft on these engines.

Many cars have a square keyway on the crankshaft snout that matches with a square keyway on the balancer. The square keyway type is super simple to put together. You start the key in place, put on the bolt and walk it into position with the bolt.

MB engines, at least the 123diesels, have two dowel pins that match up half of each hole in the crank snout with the other half of the hole in the balancer. What commonly happens is that some gorilla comes along, looks at the pins, lines them up by eye, starts the bolt and walks (forces) the bolt down to pull the balancer into position, probably with an impact wrench. In the course of turning the bolt, however, the balancer rotates slightly resulting in misaligned holes. The parts are all a little soft, so when the bolt pulls everything snug and out of position if they torque down hard, the bolt will pull it mostly into place.

This Jake Leg procedure usually results in a broken crankshaft snout, balancer coming loose or both.

The CORRECT procedure is to take the adequate time and trial and error approach to put the balancer in place slightly counter clockwise from its ideal position, so that the rotation of the bolt slipping on the balancer turns it slightly into proper alignment.

This is NOT a job for an impact wrench. If you see someone getting NEAR that bolt with an impact wrench, tell them to STOP, and sweep together your pieces and find someone with an IQ above 75 to complete the job.

In your case, you MUST use a harmonic balancer and remove the balancer to assess the condition. If there is any crankshaft snout remaining, make sure the dowels are okay and take the necessary time to put it together correctly or I can guarantee that you will eventually be very sorry.

Best of luck,

Larry, Thanks for the information. This happened on my '86 300 SDL. I did check the threads on the bolt and inside the crankshft, they are both fine. I did reassemble it and torqued the bolt back in at 200 ft. lbs. with some loctite. What is troubling me is that the balancer was slightly forward from the front edge of the crankshaft. It looked like the last person used the belleville washer to achieve this offset. This was evidenced by the marks on the washer. Should the edge of the harmonic balancer where the washers stack up line up flush with the end of the crankshaft. I put it back together but I am not sure if the balancer is supposed to be flush with the edge of the crank or offset the way it was. The service CD was not very clear on this. Is it possible that the harmonic balancer walked forward slightly for few seconds that it was running? Thanks, Tom

Have you owned this car since new? If not, I STRONGLY RECOMMEND THAT YOU PULL THE BALANCER AND ENSURE THAT IT IS KEYED CORRECTLY!!!!!!!!!!!

The fact that the balancer is not flush with the end of the crankshaft snout is even more evidence that it is not pinned correctly.

If it is NOT pinned correctly, the results can be destruction of the crankshaft snout. The only remedy at that point is crankshaft replacement. You don't want to go there!

Proceed cautiously,

Larry, I will disassemble it this weekend if I can find the time and check it out. You are correct, I do not want to do a crank replacement. Thank you for the advice, that's what makes this site so great. Tom

Tom, I can't believe I'm seeing this. I have been fighting this for some time now. I'm betting you have a non-turbo 300. Thats what I have, with identical problem. Fortunately, there is a fix.

You don't say, but were your pins sheared axially? What happened in my case is that the balancer bolt works loose and allows the balancer to free wheel on the crank end. This wears the I.D of the balancer and wears and/or scores the crank end. I tried to replace the balancer (new, with pins, bolt, washers) over $200. Torqued the heck out of it (probably incorrectly, as Larry has pointed out). But probably didn't matter, as once you have wear, It wont stay long. Mine lasted a week. Also I'll bet your bolt threads are shot.

I learned of the fix from CHAPP, who had the same problem, and will probably weigh in here. ( By the way, thanks CHAPP).

Which is to have a Diesel mechanic/ Machinest redrill and repin a new wheel in place. May even add two more holes and pins, for a total of 4. It has worked well for CHAPP. Mine comes out of the shop today. Hopefully, I will have same luck. Also, a super hard paste is added, which takes out up to 10 thou. of play. Supposedly titanium paste, available from Cat. Diesel. I'll ask my mechanic where it came from. As Larry says, the alternative is crankshaft machining or replacement, both of which is obviously expensive.

E mail me if you have any more problems with it. I don't think there is any other fix, if you have wear on the crank end.

Good luck, Andy.

I didn't read your second reply, 300 SDL. Still if you have any wear at the crank/wheel interface, it will allow movement and shear those pins like butter. When it happened to me I was at speed and heard a loud squeal, by then the damage was done.

Pull the balancer, when you replace it, if you can just slide it on by hand, it is way too loose. If so, try a new balancer. If that is also loose, you will have to have it redrilled (to enlarge the holes) which allows larger & stouter pins. This is of course a last resort.

If you know what the crank end dia. is supposed to be, you could mic. it.

Good luck.

This happened to me recently. I only found two of the washers, both appeared to be flat. I ordered a new bolt, three washers and crank seal. The washers are stamped "Mubea" (should be the manufacter) and appear to have a slight bevel.
I can only assume the washers have to be installed with the beveled side down, in other words, they will appear convex when against the balancer.

Alan '85 300D 123.133

very suspicious of any hb that has come loose. i think good chance of a ruined crank. wont hurt to try the repinning and such but if doing that i would not take off on a coast to coast trip until i have put some miles on it to see if it will last.

the only reason to fool around with any of those band aid solutions is that the only other "correct" cure is a tear down of the motor and finding a good crank somewhere else.

been there, done that. po had buggered it.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Well, I need to wear my reading glasses when flipping through the engine manuel. The answer was right in front of me, bolt and washer(s).
The beveled side faces down, so as the bolt is tightened, they will flatten and create tension like a lock washer.
In addition to ordering the above items, I also ordered new dowel pins and a vacuum pump gasket.

Without going into too much detail, as the process has been discussed in depth by Larry Bible, I can say the repair was not too difficult. After removing all belts, fan, shroud, crank pully and balancer, I used an angle drill with left hand bits. The drill has to be reversable, the bit is designed to spin counter-clockwise, and will usually catch the bolt and turn it out. This was the case, and made the job much easier. I did have my easy-outs on standby just in case.
The difficult task was keeping the pins, balancer and crankshaft aligned as described in Larry's post.

Alan

Heh...mine un-did itself twice. the third time it broke about halfway into the crank, so I decided on a new balancer and pulleys. After the 4th time, I said @#$%#$^ and started looking for another engine.

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09 Jetta TDI
1985 300D

I'm not sure if this is the same circumstance, but maybe?

While driving my 1983 300SD Turbo, my crankshaft bolt came out, and the harmonic balancer fell off of the crank shaft. I heard the bolt drop and the steering became stiff and the battery light came on, so I pulled over and shut it down.

I pulled off the fan and fan shroud & the only thing holding the harmonic balancer on was the belts. I have a crankshaft with two notches on it and am wondering what parts i need to put everything back together..

I'm assuming a woodruff key, crankshaft bolt & crankshaft seal. Anything else?

Also, does anyone have schematics for this?

I had mine come off because I left a socket + breaker bar attached to it, forgot, then re-started the engine, it loosened it and dropped it on the floor. I put it back in and torqued the daylights out of it (well beyond the 155ft/lb max of my torque wrench)....no problems since, that was over a year ago.

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There should be 6 or 8 smaller bolts surrounding the big bolt. You will need 2 dowel pins (not square key). The holes for the pins are not exactly 180 degrees from each other!! So please triple check, before you put it back together.

Oh...and you'll need a big ole torquewrench too.

__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

Soaking the balancer to 250F (I used a convection oven for about 1-1/2 hours) lets you slid it up to the dowels, twist a tiny bit and slide it home if you're quick. Then you're sure it's indexed right. Don't forget leather gloves and a hot mit. Less than a complete soak to 250F and it feels the shaft, contracts a bit and sticks.

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