Are you saying that new bolts with a higher hardness would be better? I thought the harder the brittler, and in this instance brittle I don't reckon is a good thing.
Perhaps I shall see how much some new OEM crank pulley bolts are, and look into replacing them one by one. TangoFox- What color threadlocker would be sufficient, what direction are the threads, and what torque spec for the bolts? Are they likely to be siezed inside their threaded holes, necessitating liberal application of penetrant, and what are the chances that trying to loosen them will cause the heads to break off? I'd be interested in nipping this one in the bud, but as far as I know ain't nothin broke yet. I currently have no vibration issues, nothing that would cause me to worry, but then again I haven't really checked things out. It is beyond measure how much I care about this car, and this particular failure is disconcerting.

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'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

Well - It’s 1330 central time, and I’m into the beer!!

Things with the repair were going so good there for awhile but then…………Ooops. Ok - maybe two Ooopses.

I center punched the first stud just fine. Got the drill to it and it drilled just fine. #2 easy-out pulled the stud right out. I’m think’n this is going way too smooth. Second (adjacent) stud. Center punch. Drill. Looks like I may bust the easy-out, so I step up a size. Go to drill and the drill catches the stud and before I could get my finger off the trigger, I drive the stud into the front crank seal. Ooops. But after that the stud comes right back out. Go 180, thinking I’ll now be pulling the balancer off, and that one snaps my easy-out off in it. Ooops (again). But so far I’m not teaching the world any new dirty words. Go 180 out of the first stud, thinking this one has to come out or I’ll never get my puller attached to the balancer, take my time, all’s well. Out it comes. ½” breaker bar and a 24” pipe loosen the bolt, no problem. Attach the puller bolts, the puller, and the balancer pulls right off. Sure enough, I’ve pushed the seal back about 3/16” on one side. It’s been leaking (for years), so it needed attention anyway.
Why those two alignment pins on the balancer don’t go all the way down the shaft is beyond me. If so, it would be a snap to align and install. Oh well. That’s another day.
Crank is set to #1 TDC so getting the balancer on straight (not 180 out) shouldn’t be an issue. I’ll scribe the pins to help get them aligned before I start pushing/pulling it on with the bolt. May take a couple of shots to get it. Oh-well. Also thinking of milling the pin ends to help it align itself if I’m only off a smidge.
Good news is, the balancer is off the engine, so getting the other 3 studs out will be much easier on the drill press and the bench. I can even hit them from the smooth back side and not worry about hitting the center of the broken surface with the punch.

As for doing this from the bottom, I don’t think so. It’s blind drilling with your hand pushing the drill while also pushing against the A/C condenser as it is. With the A/C hose and the radiator lower frame mount piece running across there, I think this may be a “from the top” only job. For me it is anyway.

I wont have the new bolts and crank seal until Tuesday, and am heading out of town for the weekend. This job will have to wait until next week to finish. So far, I’d call it a bigger inconvenience than anything else.
It’s all just nuts and bolts. Righty-Tighty - Lefty-Loosey stuff. There are worse repairs that could be made to a 123 I‘m sure. I’m thankful that this one requires no special M/B tools. My HD steering wheel puller pulled the balancer, no problem. ½” drive breaker and a 24” pipe turned the bolt. I’ve been cussing the slight seal leak for years now, so that’s going to be addressed. Haven’t set out to mount that balancer yet, but so far - all is well.

I’ll keep you folks posted when I’m back into it.
Thanks again for the helpful replies. Have a safe Easter weekend.

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1980 300D - Veggie Burner !

d. delano,

The pulley bolts are right hand thread, M8 x 30mm on the 617.95 engine. The ones on my car were "ordinary" grade 8.8 socket head cap screws with a black oxide finish. When I removed them, they were only "finger tight" as soon a I broke them loose. But mine were completely rust free. I used Loctite Blue on the installation. The bolts showed no signs of thread locker originally, and the service manual does not call for it. The service manual lists 25Nm torque on one page and 35Nm on another page. (The page that shows 35Nm also lists the bolt length incorrectly as 65mm, so 25 Nm is probably the correct figure. That (25Nm) agrees with the typically listed maximum torque for a grade 8.8 M8 bolt.)

I think your concerns about brittleness are not necessary. A stronger bolt is a stronger bolt. As far as hardness goes, there is only a slight difference between grade 8.8, 9.8 and 10.9. In fact, in those grades, there is an overlap between the minimum and maximum allowable core hardness anyway. So an 8.8 at the upper limit could actually be harder than a 10.9 at the lower allowable limit. There is a significant jump in hardness at the 12.9 level, but the overall strength is about 50% greater than at 8.8.

But I don't think that bolt strength is the issue. I think it's torque. As long as torque is maintained, the pulley, damper and balancer are clamped tightly together so that there is little shear loading on the bolts. It's when torque is lost that the failures occur, I suspect.

I don't think there is much chance of breaking the heads off. Stripping the internal hex with a cheap allen tool is a more realistic concern.

If you replace the seal, I would highly recommend replacing the crankshaft spacer ring as well. Or at least removing the old one and turning it around to reposition the worn area. Put the new seal in first, then install the spacer from the front of the seal. The lip on the back of the seal does not like to slide over the spacer if it's already in place.
I got my old spacer ring out by prying simultaneously with two flat screwdrivers 180 degrees apart. One at a time did not work!!! A little penetrating oil can't hurt, either.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1PY1E2LZD1S20X5BUG&year=1980&make=MB&model=300-D-002&category=A&part=Crankshaft+Seal+Spacer

Roger that. I'm in this far - might as well tag all the bases.
Thanks.

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1980 300D - Veggie Burner !

Don't worry about putting on the balancer upside down. The two pins are not at 0° and 180° - they are more like 0° and 183° (give or take a degree or two). If you eyeball it really close, you will notice it.

Good luck!

-Larry

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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

Thanks I'll do that. I got my sailing instruction on a 22' Dolphin on Lake Thunderbird(I guess you're from TX so you might know where that is, just east of OKC). I live right by there and my family and I are members of the sailing club. I've sailed a few sunfish and one laser. I've never sailed on Texoma but I've been camping/fishing down there more times then I can count. I'm joining the club at my school(University of Oklahoma) when enrollment comes around this summer and I'm going to rack up a lot of hours on Laser-type boats. I'm actually planning on buying one when I get back from my graduation-present-to-myself-vacation and see how much money I have left. I'm not sure how much help I'd be but I'd love to come out and learn.

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Seth

1984 300D 225K
1985 300D Donor body
1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!!
1980 300SD 311K My New Baby.
1979 BMW 633csi 62K+++? Dead odo

For aligning the balancer on the way back in get a couple of longer same thread bolts as these little six and cut the heads off. Lube the new homemade studs a little and put them into two of the holes. Slide the balancer on over them, put in a couple of the retaining bolts, remove your guide studs, proceed. Makes lining things like harmonic balancers and fan pulleys SO much easier.

A little bit of work loose over the years will be enough to shear a small bolt like these. A good maintenance/preventative regimen would be to replace them before they break or at least be sure they're torqued now and then.

--------------------------------------

I know Lake Thunderbird at Norman. Big surprise to me from SF bay area to find a little hotbed of sailing activity out in the middle of Oklahoma! I spent a total of just under six months over ten years attending seminars at the University.Fished the lake a little bit but never got on the water for lob (lack of boat)

i would be concerned about the hb. if it were wobbling a little that would maybe shear the bolts.

so when it is all back together i would take a hard look at it to be sure it is not wobbling. also i would put new pins in.

and finally one more time... be so careful instlling the hb with its pins. it is extremely easy to damage the nose of the crank and then you need a new crank. one car i bought for parts had this. i was planning to rebuild it anyway but before that i had to find a new (used) crank because someone before had ruined the keyways and pins.

the hb wobbled a bit at idle.

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.

Krs,
What do you screw those "homemade studs" in to?

I can’t see how a wobbling HB would require a puller to remove it. Seems to me that if it can wobble on the crankshaft, it would be able to slide off by hand. Mine was tight as a drum, and the puller had to work to get it off. Nothing “nasty tight“, but it was tight all the way to the end.
I guess the big bolt is what pulls it back on. That wanting to turn the HB on the crank is what makes it such a pain to reinstall. Maybe a dead-blow mallet might get it down to the pins, but that may be more blows to the crank/bearings/etc than I want to inflict. I’ll need a new way to hold the crank from turning, for sure.
Aligning the pulleys to the HB should be no problem. I’ll either do like KRS said or use my T-Handled allen drivers to hold the first bolt through the hub. Thread it a few turns and shoot the second bolt.

It’s pushing the HB onto the crank that seems to be the big issue.

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1980 300D - Veggie Burner !

The HB, I'd say. His idea would help align the pulley assy to it. I don't think my fingers want to reach in there to get them out though. They'd need a slot for a screwdriver in them.

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1980 300D - Veggie Burner !

What’s the story on the front seal spacer? Should I replace it? I’m thinking “yes”, as I’ll be right there.
Does it get lubed up and pushed in after the new seal is in place? Or, does it go in first, and I take my chances with the seal not going around it? What does it space? Seems to me it controls the depth that the HB is inserted into the block/seal onto the crank. If so, it seems to me it would be back far enough to not contact the seal, as the HB goes all the way through the seal. What part of it actually wears? I’m thinking the ends might, but isn’t it rotating with the crank/HB? Sorry about the zillion Qs here, but I just want to make sure I’m not missing something important. This forum seems to be the ultimate place of information for us DIYers. My thanks to you all.

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1980 300D - Veggie Burner !

The lip of the crank seal actually rides on the spacer. So the spacer likely has a groove worn in it. Depending on the extent of the wear, you might be able to turn the spacer around so the seal lip has a "fresh" surface to ride on. (On mine, the groove was almost centered in the spacer (albeit offset slightly) so I did not feel that reversing the spacer was a wise move.)

But the spacer really needs to come out, regardless. The design of the rear seal lip is such that it will not easily slide over the spacer if the spacer is already in place. It is much better to install the seal first, then install the spacer from the front of the seal.

What does the spacer space? It fits between the chain sprocket and the balancer. The balancer will bottom out on the spacer, which bottoms on the chain sprocket. The balancer absolutely does not go all the way through the seal. The rear lip seals on the spacer, not the balancer.

As far as the balancer alignment goes, you can't really see how things are going until the balancer is on far enough for the pin holes to start matching up. I found that it was best to make adjustments by pulling the balancer most of the way off, but not all the way. Then I could tap the balancer to rotate it slightly in the appropriate direction, then draw it back down with the big bolt. Repeat as necessary. Don't pull the balancer completely off, as you will loose your "frame of reference" and be back at square one. I greased the large washers on the crank bolt and I had little trouble with the balancer rotating as it was drawn on. There is so little tolerance in the alignment pins that it only take a fraction of a degree error and they are not going in. Patience will be your greatest asset.

ThanksTF007 !!
That's what makes this board great.
All is pretty much as I say it to be, with the exception of the spacer and it's relations with the other parts. Thanks for making it all clear.

So - as I'm tightening up on the HB bolt - what do I do to hold the crank from turning? Jam the flywheel/TC with something?

If I don't reply back today, I've left for the ranch. I'll be back Sunday night to catch up.

Have a great and safe Easter Weekend to all. Thanks again.

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1980 300D - Veggie Burner !