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  #1  
Old 04-01-2004, 09:51 PM
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Location: Houston, Texas
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Unhappy Is it possible to retap the 27MM crankshaft pulley hole where bolt fastens?

Here is the situation. The car is an '82 240D. This week the crankshaft pulley became loose so I investigated to find out that the 27MM bolt that holds the pulley in place became loose. The engine would run but the pulley wouldn't turn. The reason that the 27MM bolt became lose was because the bolt's threads and the threads inside the crankshaft hole where it screws appear to be damaged and somewhat stripped. I don't know how this happened other than maybe the previous owner took the crankshaft pulley off for some reason. Anyway, my question to the group is: Is it possible to retap the threads for the crankshaft pulley hole where the bolt goes in? I was thinking that if I buy a tap and a new 27MM bolt that this would save the car. Is is possible to install a helicoil or is the crankshaft made of super hard steel and be impossible to drill to install the helicoil? I like the car alot and would hate to think that this would be the demise of of the car just because of one damaged bolt.

Any advice?

Herb
'82 240D
'87 300SDL
'92 300D 2.5 Turbo
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  #2  
Old 04-01-2004, 10:52 PM
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I may be mistaken but I am under the impression that there are two pins that lock that pulley to the crank? They slide into half round grooves on each part.
Anyone confirm this?
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  #3  
Old 04-01-2004, 11:26 PM
Bruce Lane
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Keys

I am not sure how it is driven put what Kerry is saying is a very strong possibility, and what he is discribing are called a woodruff key. Usually one is used to drive a pulley, gear or sprocket. They are used on many engines and other machine devises. I dought that the pulley would be drive by the bolt alone. Take the pulley off and look at the shaft and see if there is a half round slot "keyway" that is machined into the shaft. The key would take all the torque that is applied to the pulley. The bolt just holds the pulley on the shaft. If the bolt has the threads damaged there may be enough threads in the crank to hold a new bolt with good threads. It would not have to be very tight to hold the pulley on with the key doing the drive.
Good luck.
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  #4  
Old 04-02-2004, 12:00 AM
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Look at this thread. The pins hold the harmonic balancer in place and it looks like the pulley attaches to that balancer.

Failed 123 Diesel Harmonic Balancers
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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  #5  
Old 04-02-2004, 05:36 AM
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Quote:
Originally posted by kerry edwards
I may be mistaken but I am under the impression that there are two pins that lock that pulley to the crank? They slide into half round grooves on each part.
Anyone confirm this?
Yep, the two round pins keep the balancer from spinning on the crankshaft snout and the large bolt keeps it tight.

You can "chase" the threads with the proper sized tap to clean out the debri and then use a new bolt with a drop of red locktite.

If it won't hold the proper torque you MIGHT be able to install a "time cert". They are a bit heavier than heli-coils and more reliable. Drilling and tapping the crank end may prove to be tough, but not impossible.
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  #6  
Old 04-02-2004, 07:18 AM
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You would need 10 foot long lever to damage the threads on the crankshaft bolt, I'm betting the key broke.
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  #7  
Old 04-02-2004, 08:00 AM
LarryBible
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There is no Woodruff key. There are two dowel pins.

This bolt is supposed to get a few hundred pounds of torque so when you chase these threads, proceed carefully and get it EXACTLY RIGHT!

Even more important to point out is what I said in the first sentence. Many of these crankshafts have been ruined by someone putting it together as if it were a Woodruff key. They slap the pins in, throw the balancer on, start the bolt and run it in with an impact wrench. It would be a pretty safe bet that this is what led to the failure in the original post.

What you MUST do to begin with, set aside plenty of time to get this balancer on correctly and have a harmonic balancer puller close at hand and plan on possibly using it a number of times. Place the balancer carefully on the crankshaft snout slightly counterclockwise from pin hole alignment. Start the bolt and run it BY HAND down a good bit and then remove the bolt and see if the pin holes align. If they are close enough to seat the pins with light hammer tapping, then put the pins in place and then replace and torque the big bolt. If the holes are not aligned, pull the balancer and try again.

If you do not do this carefully, you have a great chance of destroying the crankshaft and the balancer. The balancer seems to be harder than the crankshaft. I think it is steel vs. the crankshaft being cast iron, so the balancer will probably not get hurt, it is the pins and crankshaft snout that get destroyed.

PROCEED CAREFULLY and DON'T get in a hurry.

My $0.02,
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  #8  
Old 04-02-2004, 08:23 AM
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To start with that is an 18MM thread & you can get a tap that size from snap-on, mac, & others.

AS Larry stated it is the 180-200ftlbs of torque that holds every thing together, not the alignment dow pins.
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  #9  
Old 04-02-2004, 08:50 AM
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I'm glad I asked you guys. It sounds like there is still hope to revive this sick car.

I found the pins on the harmonic balancer sheared. The halfmoon cutouts on the crankshaft appear to be ok with no damage. I will need to get a brand new harmonic balancer and a brand new crankshaft bolt. I will also need to get an 18mm tap as per MBDOC advice.

Also, Larry, are the alignment pins welded to the balancer? Or are they separate pieces of metal that must be inserted? The reason I ask is because I found evidence of what was left of the pins "stuck" against the inside of the balancer like as though it was welded but I couldn't tell.

In addition, is the crankshaft made out of hardend steel?

Thanks guys,

Herb
'82 240D
'87 300SDL
'92 300D 2.5 Turbo
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  #10  
Old 04-02-2004, 09:03 AM
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Larry,

After reading your post carefully. I answered my own question about the pins. From your post, it appears that they are inserted and not welded to the harmonic balancer.

Herb
'82 240D
'87 300SDL
'92 300D 2.5 Turbo
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  #11  
Old 04-02-2004, 09:06 AM
LarryBible
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The pins are separate items. As I described, once the balancer is in position, you tap them in place then replace and tighten the bolt.

I don't know the material of the crankshaft, but I know that the snout is a little soft and can bugger up if it shears these pins. As MB Doc described, the pins simply locate the damper in the proper position, and then the bolt holds everything in place.
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  #12  
Old 04-02-2004, 10:46 AM
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Last year when I was rebuilding the engine in my wifes 240D, I had read about the proper way (Larrys post) too put on the harmonic balancer and it did take a long time , put it on, take it off, put it on, take it off, put it on, take it off, put it on, take it off, put in on....Aaaahh, the pins go in ..finally .... You get allot of practice with the puller

Steve
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  #13  
Old 04-02-2004, 11:05 AM
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Quote:
Originally posted by leathermang
"There is no Woodruff key"

Wrong.

Have you considered looking at the picture in the shop manual ?

Item 27 in the picture....

I think we are referring to the same thing as the pins that Larry Bible is referring to. I counted two places on the crank where the pins need to be inserted. Is there another place where a Woodruff key is inserted or am I missing something?

Herb
'82 240D
'87 300SDL
'92 300D 2.5 Turbo
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  #14  
Old 04-02-2004, 11:17 AM
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Another question regarding the 18MM Tap from the posts above.

What is the pitch size for the 18MM tap for the crank? Is it a 1.5 or 2.0 or some other size?

Thanks

Herb
'82 240D
'87 300SDL
'92 300D 2.5 Turbo
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  #15  
Old 04-02-2004, 11:34 AM
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Larry,

A cast iron crankshaft? That would probably last until the first cylinder fired.

A crankshaft is forged steel and the Turbo Diesel crankshafts have the bearing journals nitrided for a super hard no wear surface.

P E H
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