Here is my complete Crank Fix..

[sdezego]

Quick premise: Crank bolt snapped getting up to speed on interstate. Pulley key wasted and crank Key slot partially boogered.

here is my fix pictorial:

Parts:
- New Crank Pulley - VW (049-105-263-C)
- New Crank Bolt - VW (N-903-208-02)
- All New Belts
- Loctite (Stud and Bearing mount)
- 2 STD Roller Bearings (mid '70-'s Harley Sportster Trans Mainshaft)
- Brake Cleaner

Special Tools:
- Good set of Cobalt Drill bits
- #5 Easyout (5/16) with 19/32 drill bit (if needed)
- 1/16, 5/64, 9/64, 5/32 Cobalt drills (if not in set)
- Flywheel lock (if you have one
- Torque wrench
- Center Punch
- 14mm x 1.5 Thread Tap (if needed)

Steps:
1- To make it easy I removed: the timing belt cover, the Serp tensioner, right from wheel, lower timing belt cover and inner fender well.

2- Using a center Punch I made a mark in the exact center of the broken Crank Bolt. I started with an 1/8 pilot drill bit and worked my way up to 19/32 to extract.

3- I then took the new crank Pulley on the drill press with a 1/16 drill bit and drilled one hole opposite keyway and all the way through (you can use 2 dowel pins if your crank is really trashed). I drilled the pilot hole so it would be in the center of the crank between the crank bolt hole and the outer edge of the crank (SEE Hind Sight Notes at bottom).

4- using the 1/16 drill bit and the crank pulley placed on the crank as a template, I drilled the hole in the crank to a depth of 1/2 the length of the dowel pin.

5- I then used the 5/64 drill bit in the same fashion, drilled all the way through the crank pulley (using it as a template) and then into the crank to the same depth as #4.

6- using the 9/64 drill I drilled the crank hole out (not using the pulley this time) to same depth as above (1/2 the length of the dowel). Go back and forth a few times to make the hole a tad bigger. You could probably go to the 5/32 drill for the crank only so the pin slides right in, but I wanted a tighter fit.

7- using the 9/64 drill I drilled the crank pulley hole 1/16" more then 1/2 the depth of the dowel from the Backside out. This will prevent the dowel from backing out and allow and easy way to drive the dowel in to the proper depth in the crank pulley.

8- Drive dowel pin(s) into crank pulley

9- Tap crank threads (14mm x 1.5) to clean them up if necessary. I needed to because when the bolt snapped, it slightly screwed up the first 2 threads. The bolt must screw in perfectly by hand to be able to torque properly.

10- use brake cleaner to clean everything. I then used a small amount of Loctite stud and bearing mount on the crank key slot, than mate surface of the crank pulley and crank and then used regular red (271) on the bolt.

11- Torqued to proper specs (66 Ft'Lbs + 1/2 Turn) using homemade flywheel lock.

Hind Sight notes:

1 - If your crank key slot is really bad you may want to use 2 dowels on either side of the crank (away from the old crank key slot).

2- If I had to re-do, I would probably have drilled the dowel(s) closer to the outside edge of the crank (further away from the crank bolt). This is because there is less shear force the further out you go from the cranks center point. I was worried about being too close to the end of the crank, but in reality, that's where the stock keyway is...

This is just me over analyzing things as it will likely never matter anyway..

Good luck and be patient if you try to do this as well. A broken drill bit in the crank will give you a world of hurt. (light pressures to drill and straight holes)

Shawn

[brilliantyellowg60]

thanks, i will be doing the same, but using 2 pins as the crank isnt lookng too good

i will try and get pics too

[Alpineg60]

OOPS! WHEN i WROTE TC/J that is the shear in the crank pulley itself not the pin, that is alot more complex dynamics prob i think regarding contact forces, and inertial forces. D'Alemberts principal.

sorry

Modified by Alpineg60 at 1:37 PM 9-20-2004


Modified by Alpineg60 at 8:55 AM 9-21-2004

[marat_g60]

great write up!
now i can go ahead and fix mine too so it will never happen again

[sdezego]

Quote, originally posted by Alpineg60 »

Actually the further out from center you go the more shearing force (rotational shear = Tc/J) where T is torque, J the polar moment of inertia, and c is the radius. The location of the key being close to the center is probibly the best design, that is where it experiences the least shear. Modified by Alpineg60 at 1:37 PM 9-20-2004

I hope you didn't get a good grade in Dynamics or machine Design Your equation is fine and you are on the right track to support what I am saying. What you failed to look at was the Value of J (the polar Moment of inertia). For simplicity, to consider the Key as a hoop at a radial distance r (or c in your equation), the equation for J is:

Notice that the radius in J is to the 4th power! This is the reason why drive shafts are hollow and have large diameters. The material at a small radius does little to resist shear. If you were correct, everyone would be scurrying to change out their 100mm CVs for 90's If you want to read up check out this link (spec. pages 8 and 9). http://ocw.mit.edu/.../torsion.pdf

Shawn

[bulldog2.G]

"shear" can be thought of even more simply by thinking of, as illustration, a set of "shears" or scissors. It is easier to cut a given material at the beginning of the shears travel, closest to is axis. The further away from axis, the more force necessary to cut the same material. It is leverage dependant.

Don't challange Mr. Shawn !!!

[sdezego]

Quote, originally posted by Alpineg60 »

OOPS! WHEN i WROTE TC/J ...... sorry

No worries (if I was your professor, I would have given you partial credit for thinking in the right context), but you do owe me a for making me think so hard.

Shawn

[corradokyd]

well done. i like seein some sht get done right with busted knuckles...

[G60 CAB]

Thats what I did, except I used two dowel pins!

[sdezego]

Finally been able to drive her a bit. Man was it a joy. Decided to do the rod bearings while I had the pan off (Pan was damaged from the tow home) and fix a couple of coolant hose issues and such. A new pan was only like $15 from Autotechparts!

If I could focus for any amount of time, I would be able to build up my ABA

Shawn

[bhwang]

I'm having my supercharger rebuilt by KK at the moment. Dave from KK recommended that it might be a good idea for me to change out the crank bolt.

When I went to the stealership to get one, they recommended that I also replace the crank pulley as well. Is this really necessary? It's like $150 for one of those suckers.

-Burt

[sdezego]

That doesn't sound correct.

It is not a bad idea to change the cog, but if thats what they were quoting you, it's only about $15-20 aftermarket (autotechparts.com). If yours is in perfect shape, there is no real reason to change. The only way to know for sure is to take it off and inspect the keyway.

Part number listed in first post.

S

[MikkiJayne]

Interesting! I thought this only happened on TDIs...

Shame I can't drill straight, otherwise I'd do this too

Mikki x

[sdezego]

Quote, originally posted by MikkiJayne »

Interesting! I thought this only happened on TDIs...

Sadly no. It is very common on the G60's. Especially, when the mileage is > 100k miles.

Too many cycles on the stretch bolt I guess.

[Issam Abed]

Quote, originally posted by sdezego »

Sadly no. It is very common on the G60's. Especially, when the mileage is > 100k miles. Too many cycles on the stretch bolt I guess.

And its now starting to become common with the 20V's

[sdezego]

You want to know something very peculiar too?

If you look at the Bentley on an ABA vs a G60 (both use the exact same bolt and cog), you will see that the specs are:

1.) G60 = 66Ft/lbs + 1/2 turn
2.) ABA = 66Ft/lbs + 1/4 turn

Go figure...

I don't think VW knows/knew wtf

[jmaddocks]

Quote, originally posted by sdezego »

You want to know something very peculiar too? If you look at the Bentley on an ABA vs a G60 (both use the exact same bolt and cog), you will see that the specs are: 1.) G60 = 66Ft/lbs + 1/2 turn 2.) ABA = 66Ft/lbs + 1/4 turn

It's almost as if some lowly bolt engineer at VW pulled the specs out of his butt!

[MikkiJayne]

Or manual writer at Bentley Publishers

The theory with the TDIs is that the rotating mass of the alternator puts a load on the crank during firing cycles at idle (ie crank slows, but the alternator doesn't). The load puts stress on the sprocket and the bolt is the weakest link.
The fix on the TDI is a one-way clutched alternator pulley which allows the crank to change speed without any inertial load from the alternator (ie the alternator spins freely under its own inertia when the crank slows down).
This pulley was fitted to 98> TDIs I think, and apparently some VR6s.

I'm not that surprised that it can happen on the G60, as that has a fair amount of rotating mass too, plus an alternator. Odd that it can happen on the 20V too though?

Mikki x

[sdezego]

That's is interesting. I have seen the "one way" clutched alternator drive bearings used more and more, but don't think about it in this case.

Shawn

[DJ Appa]

What a good thread I wiped 2 heads never once thought to check to even see if the key was worn

My problem was the pully kept getting loose and the timing belt stopped spinning so I thought it just was'nt torqued right

[swingwing205]

Quote, originally posted by sdezego »

Sadly no. It is very common on the G60's. Especially, when the mileage is > 100k miles. Too many cycles on the stretch bolt I guess.

Are you saying you think that the bolt @ the crank stretches still more over time, given many cycles? It should be a recommended change out item at certain maintenance intervals then (like for instance, at a timing belt change), esp since this effects other VW engines like the TDI's and 20v's.

The more I start to think about that, the more I'm thinking it's like "timing out" parts on aircraft (as I'd guess there's no good way to figure out Torque Events on a car, so timing the part out would be the only practical solution...). But, the G60 is a finicky beast, and you do have to kind of look ahead.

Do you think it's because of the load of the supercharger constantly on the crank then? It couldn't be just the valve drive train load. I've always kind of thought that was possible.


Modified by swingwing205 at 11:16 AM 11-29-2008

[sdezego]

I personally think it is a little of everything you mention.

If you look at the failures (and I have inspected quite a few), you can see hoe the fracture of the bolt propagates. Look at the pic above and you can see the fracture which is text book fracture mechanics that originates from too many cycles, stretches, necking, etc..

[swingwing205]

Quote, originally posted by sdezego »

I personally think it is a little of everything you mention. If you look at the failures (and I have inspected quite a few), you can see hoe the fracture of the bolt propagates. Look at the pic above and you can see the fracture which is text book fracture mechanics that originates from too many cycles, stretches, necking, etc..

My thoughts too, we're def on the same page.

The regular 8v's seem immune from this problem, but think about the fact that they have close to nothing to drive, other than the valve drivetrain. The G60's and TDI have all that and both have extra heavy duty appliances to drive, the Supercharger on the G60's and the Injection pump on the TDI's, both of which put some real load on the crank.

Now, I'm wondering about the 20v's, why they would have so much trouble, as they're doing something very similar to the problem discussed here. Maybe extra heavy valve drivetrain load? I wouldn't think it would be much if any more than the old 16v set up, but I could totally be wrong.

Well, that settles it. When I do my Timing belt on my G60, I'm changing this crank bolt out as well. Wish me well guys, and hope that this prob isn't already started on my car ( I don't think it is, but...).

[sdezego]

The TDi's and 20v (06a block) uses a larger bolt.

[sprocket007]

When I do the timing belt I change all the engine seals on that side and the crank bolt...you might as well ur there anyway and It really does not take that long.
Wade

[swingwing205]

Quote, originally posted by sprocket007 »

When I do the timing belt I change all the engine seals on that side and the crank bolt...you might as well ur there anyway and It really does not take that long. Wade

...And seems like VERY cheap insurance. Way to go VW....

[lloydbiker]

Am I right in assuming you used bearing rollers as dowel pins, and also used an aftermarket (solid steel, not sintered) crank gear? Just how hard is the crank nose?

[Z-Raddo G60]

i replaced the original crank bolt for the crank pulley from the original "stretchy" to the non stretch and washer...

how will this compare?

edit:

btw, great discussion...nice write up


Modified by Z-Raddo G60 at 1:17 PM 4-5-2009

[lloydbiker]

Personally, I would not. There was a reason to go to the torque-to-yield bolt. They tried that as the first stage fix, but it didn't do it. Those bolts are not cheap, and they are the sub for all previous equipment. Number one, I believe they are higher strength , to begin with.

[Z-Raddo G60]

Quote, originally posted by lloydbiker »

Personally, I would not. There was a reason to go to the torque-to-yield bolt. They tried that as the first stage fix, but it didn't do it. Those bolts are not cheap, and they are the sub for all previous equipment. Number one, I believe they are higher strength , to begin with.

dang...i don't like that sound...

next up for a little something...or more importantly...more specifics on it? sorry to jack this end up...

[lloydbiker]

I'm currently looking at doing this to my '97 TD (AAZ engine-seldom seen in US) with 3 pins, cutting the torque to 66ft/lb+1/4 turn (a little less stress on the bolt). I figure, if it can handle a supercharger in addition to the regular accessories, it should be good with the clunky idle and IP of the diesel. I know there's a mod using the TDI cog, but that involves machining the crank snout, (beyond my capabilities, and I'm not even sure within the local machine shop's). This I can easily do with my drill press and power drill, in the car. I'm also planning to install a 'freewheel' alternator pulley. Any thoughts or comments?

Modified by lloydbiker at 9:38 AM 4-6-2009


Modified by lloydbiker at 9:42 AM 4-6-2009

[sdezego]

Quote, originally posted by lloydbiker »

Am I right in assuming you used bearing rollers as dowel pins, and also used an aftermarket (solid steel, not sintered) crank gear? Just how hard is the crank nose?

Correct, as dowels. The crank is not that hard and drills right out with a good cobalt drill bit.

As far as the clutch type alt pulley, I personally think it is a good idea and in fact I am using one on my new 2020 motor using the whole late 1.8t alt.

[Danno13]

Can any alt be fitted with a clutch type pulley?

[lloydbiker]

In all likelihood the cog is harder than the crank, right?

[REPOMAN]

Great repair thread.
When you have alot of torque only overkill will do.

OWNED