Crankshaft Pulley Bolt: Why Would It Come Loose?

[Vanagon Nut]

Hi all.
I searched via title on this.

Have seen the results of the first hand and heard about it via a fellow camper
at a recent campout. We discussed why this would happen.
I believe he posted here about his adventure with that issue.

Bentley shows an entire page on tightening this bolt properly.

From the factory, I assume this wasn't an issue. Here's what he and I figured
were the main contributors to bolt backing out:

- torque value used was too low (no special tool, guess work deployed)
- bolt re-used too many times (it has a fine thread)
- crank key way and/or woodruff key worn beyond spec prior to rebuild/repair
- cross threading bolt on install

or ?

The sad part is that the average owner/wrencher probably doesn't have the
means to easily remove this bolt and retorque to be safe. I guess one just keeps
an eagle eye on their engine!

Neil.
_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[MidwestDrifter]

The key is only for initial alignment. In service the bolts clamping force and the resulting friction prevent the pulley and crank from moving respective to each other.

Unless the bolt is TTY, it can be reused. Most high load bolts only have 2-3 good pull downs until the thread is worn enough to affect the clamping load. When in doubt, get a new bolt!

Under-torquing can lead to keyway failure, bolt fatigue failure, or the bolt loosening. When in doubt get a torque wrench!

Over-torquing can cause the bolt to stretch plastically. This can result in the bolt breaking either immediately or shortly down the road.

Unless the manual specifies lubrication, bolts like this are to be installed dry! Lubrication can result in a normal torque level creating excessive clamping force, which could damage the bolt or the threads.

Its pretty unusual for these bolts to loosen over time when installed correctly. When/if they do; damage to or imbalance in the belt drive system is to be suspected.
_________________
2004 Dodge/Mercedes Sprinter (Custom Camper)
2000 Jetta TDI
1982 Diesel Westy W/ ABA I4 hybrid (Sold)
Epic Road Tripping since 08/05/12 | http://VagariesAbound.blogspot.com/
My Current Build | http://sprinter-source.com/forum/showthread.php?t=41215

[t3 kopf]

I agree with all the above except the no lube part. I believe that high torque bolts like these should have the threads lightly oiled.
_________________
'90 Carat w/ '95 phase 1 EJ22 OBD2 conversion

[MidwestDrifter]

[Vanagon Nut]

Oh my. Engine conversions. I don't know why I chimed in.

Ok. For sure. I see the point on woodruff key. And thats a good point on
balance in the belt drive system. I mean it's not like the alt. bracket is ever
an issue. lol.

Since the torque value is so high, and it's tough to hold the pulley dead still
without the right tool or similar, one could easily under torque that bolt.

I'm sure the event I saw and heard about are relatively rare.

Neil.
_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[jerryherb]

my main bolt came loose to the point i could remove it by hand. no damage to threads, woodruff appears worn as the pulley was banging on it. any pointers on how to get the 250lbs on the bolt WITHOUT the key no one but a specialized shop probably still has?

[IdahoDoug]

What is this "key" you want to do the tightening without?
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[dgbeatty]

They come loose primarily due to improper installation.
_________________
Schau in das Buch

[vanagonjr]

McMaster Carr has metric Woodruff keys. Check the sizing, and maybe you will luck out
_________________
John - 86 Wolfsburg Westfalia "Weekender"
Flint reversed 1.8T W/Passat 5-Speed
LiMBO (late model bus club) www.limbobus.org
LiMBO is on Facebook too! https://www.facebook.com/groups/
FAQ thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=525798

[Butcher]

The key is a lock tool to prevent the crankshaft from moving while torquing on the bolt.

[IdahoDoug]

I guess I'm not going to get an answer to my question on what key you want to do this without? Since you refer to "shop" I'm assuming you think there is some kind of shop tool (a key) to hold the pulley, etc. So I will continue into the fog of answering your question to say you can immobilize the pulley with a chain to tighten against it.
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[Wildthings]

I have some yacht braid polyester (this is not the cheap polypropylene rope you can get anywhere) that I tie off to some place on the engine and then wrap the crank pulley a couple of turns. While keeping tension on the free end of the rope you can apply torque to the nut and tighten down the pulley. You could probably do the same with some 3/32 or 3/16 wire rope, or you can cut up an old V-belt and use it.

If using rope, the closer you can tie off the rope to the pulley the less stretch you will get.

[IdahoDoug]

That's a great idea. Your technique also eliminates the chance of the chain damaging the pulley. I like it - thanks.
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[Wildthings]

[AtlasShrugged]

When you need a new woodruff key for the crankshaft they are NLA from VW. Part number 070105249

BusLab has them for $2.50

https://www.buslab.com/product-p/070105249.htm

[IdahoDoug]

If you could, I'd love to know the diameter of the rope as what you're using works and I'll be guessing. We're boaters and may even have some on hand.
_________________
1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[mellowslow]

https://www.gowesty.com/product/mechanical/24797/crank-lock-tool-for-pulley

Do you need a crank lock tool?
_________________
'87 WBWE FAS Gen V

[Wildthings]

[djkeev]

[jerryherb]

thanks for all the replies, by mistakenly typing "key" i meant the pulley tool 3102 on bentley page 13.42 . i did order the woodruff key as mine was pretty beat up by pulley banging on it hence creating the clunking i thought was coming from the TC/tranny as in my other posts. pulley grove appears ok so i will reuse it.

does anyone own the 3102 and can post the dimensions so that maybe i can build one? i have seen the GW flexplate lock, but would rather lock the pulley side than transfer 258lbs of torque through my old engine crankshaft and the TC/plate. someone did mention the cranshaft can bend. though i find it unlikely i think the pulley lock is a better and fool proof method.

would any other pulley lock work? i will investigate the rope method if i cant find any other solution

i was considering this, which obviously would require a helper, though not sure it would fit the pulley as the holes are recessed pretty far in:
https://www.amazon.com/OTC-4754-Universal-Pulley-Holder/dp/B000Q8GVPY