Pinning the Crank Sprocket

So, there should be no play at all - a tight fit?

Correct, but what I found was a loose fit until the bolt was tightened.

I documented it here, including the loose fit movement of the cam sprocket. The car on which I worked is still going strong, the crank sprocket has not moved, and the owner is reporting just under 57+ mpg.

n0ftInc said:

So, there should be no play at all - a tight fit?

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Yes, needs to be very tight... because even a little movement opens up the possibility that it will start to rock back and forth as the engine accelerates and de-accelerates... and the little movement will wear to be bigger and bigger... worst case, till valves meet pistons.

I see both sides I guess. I know the bolt should be holding it, but the keyway shouldn't have this much play in my mind.

Hmm..anyone else? If I need to send this crank back to the source, I need to start the hunt for another one asap.

I replaced my crank pulley and bolt when I got the car just to be sure.

I was lucky, as there was barely perceptible play on the old sprocket, and when I installed the new sprocket, there was no play at all.

Abacus said:

Correct, but what I found was a loose fit until the bolt was tightened.

Click to expand...

Windex said:

I was lucky, as there was barely perceptible play on the old sprocket, and when I installed the new sprocket, there was no play at all.

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Windex, was the bolt tight or did you mean without the bolt..?

Bump..?

*UPDATE*

My gear started cracking on the nose where the harmonic balances goes over it. The metal was just not thick enough and compressed when the bolt was torqued. After a while it cracked on both sides.

I blind pinned it this time. I removed the old gear and used it as a guide to drill about 3/8 into the snout side of the new gear.

You will need the following additional bits and pieces do this:
8 1/4x2in steel dowles.
Your new gear
a harmonic balancer
2 2-3in hose clamps
2 3/16 x 3/4in dowel pins.
Your old gear drilled through perfectly straight.

Use the 8 dowel pins around the old gear held loosely with 1 hose clamp. You end up with 1 every 3rd tooth with 1 only 2 teeth apart.

Bolt the new gear to the harmonic balancer as it would be on the car.

Slide the old gear / dowel pin arrangement onto the new gear aligning the holes, "D", bump, teeth etc. Secure them together with the second clamp making both tight.

The whole thing sits on the ground with the balancer stabilizing it.
Drill through the old gear into the new gear. (my old gear was drilled by a machine shop and the holes were perfectly straight. It was a great guide. If your gear holes aren't straight, this may not work for you.)

I figured out depth by taking a 3/4 x 3/16 dowel pin and pushing it into the crank snout. I used a magic marker to mark how deep it sits in the crank. I spun the pin in the crank while I held the marker to it. My pins each had a side that was more flat and one that was more rounded. I oriented them both with the more flat ends in the crank and marked the end of one with the black marker so I knew what went where. My holes were close but not exactly the same depth in the crank
Drill a bit and check the depth. I got to the correct depth in about 10 steps. You just loosen the 2 clamps a tiny bit and the old gear comes right out.

I slid the appropriate pin into the gear until the mark was 1/32-1/16in deeper into the gear. That should give me some room for expansion.

Thats about it. I have pictures if someone can tell me how to post them.

Obviously attempt this at your own risk.

How many miles on the old gear? Any pics of the crack/s

G60ing
I think I got about 15k before I found the cracks, then I reinstalled it and drove another 10k. I don't know how to post pictures. I emailed you some. Please feel welcome to throw them up here. Otherwise I'll figure it out later.


I also replaced the harmonic balancer. It's been squeaking for about 200k. So far no noise. Fingers crossed

I'll have to look at mine, I have about 10k miles on mine. It looks like I will have to pull the center bolt and redo the timing belt job to inspect?

The cracks, are on the thinnest part off the gear. If you pull off the balancer, you will see them. I'll take a picture of the old gear and send it to you.

Thanks for posting my pics for me.
The first one shows the marks I made on my pins to check depth. I drilled into the gear. until the black line was covered by the gear.
The middle picture shows the cracks, in the gear. as it sits in the driling rig.
The bottom pic showed the drilling set up

What is the fix for this problem? Had several issues with timing staying in spec and in March bent valves. Took engine apart today and found that crank gear does not have d notch any more. Have photo but cant post.

This thread is the fix, or replacing the crank.

I thought that cranking started have 25000 miles. How did drilling halfway through gear work out?

I don't think it will crack since I onlydrilled half way through the gearside where there's lots of metal . If you drill all the way through I think the metal is to thin under the bolt head. I think it cracked partially because it compressed. I've got about 8 k or so since I drilled it last time. I haven't checked it yet. Unless it starts having trouble starting, smokes, or makes noise I'm not going to check again until the front seal starts pouring, or I need to expose the belt for some other maintenance .

If your crank is boogered up, the only two choices I know of are a new crack, New engine, or some version of pinning.

For all the scary almost hype of changing a belt, it's really not hard.

I used two Allenwrenches to tension the tensioner, and markedthe cam sprocket. After everything was back together I visually checked that the cam was aligned. I used a socket for a pump lock. Craftsman1/4 drive 3/16 I think.

I put the car in fifth and pulled the e brake to hold the engine while torque-ing the crack bolt.the last two times I used an impact to rotate the 90°.

Last 4 tanks have been 51.5-53 mpg. No smoke, good power.

Do as you wish at your risk with your car, this appears to have worked good for me.

You used an impact for the final rotation on a crank you've drilled & pinned? I'm brave, but not that brave.

When I first found the crack, I put that same gear back on, with an impact. It ended up getting stuck in the balancer from mushrooming.

The last time I put it together, the impact didn't take it all the way to 90°. I endedup using a breaker bar until the socket skipped . Never did get to 90°. I marked the bolt and the balancer and checkit every month . It hasn't moved yet.

I figure the torque spec is around 500ft lbs. That's what the gun says it maxes at, and it got there a couple times.

Abacus said:

You used an impact for the final rotation on a crank you've drilled & pinned? I'm brave, but not that brave.

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That explains the cracking.

That could be why it cracked. However, does it make a difference how I turn the bolt the last 90°? It's still the same squishing force on the gear and its thin where the pins go through. By going in from behind only into the thickest part of the gear should prevent cracking and its not that much harder to do it that way.

I have a small leak behind the gear so I'll have to pull it eventually. I'll retort back how it's doing then.

I had also installed the bad balancer when I drilled all the way through. That may also have played a part in the cracks.

I believe this is a great alternative to a new crank. I would do this to a new crank without a second thought just fit longevity.

914fan said:

However, does it make a difference how I turn the bolt the last 90°?

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Can't say definitively... but I do know that anytime I've read scientific explanations about using TTY bolts they always emphasize that the stretch phase needs to be applied "smoothly"... and that you can break the final 90 degree turn into two 45 degree turns, if needed, in order to be smooth.

An impact wrench probably wouldn't be considered "smooth"... dunno if it's an important distinction in this context.

gthtdi said:

What is the fix for this problem? Had several issues with timing staying in spec and in March bent valves. Took engine apart today and found that crank gear does not have d notch any more. Have photo but cant post.

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Bump to revive this thread and to specifically ask if the above applies to your crank sprocket or to new replacement crank sprockets?

Resolved it for me

I've been doing a ton of reading on sprocket walking - looks like I'm not alone with this. I think I'll do as you suggest and use the old bolt and torque it down and give it a feel (the old sprocket didn't move until I pried it off so I don't think this will either).

I'm sure this problem is my own doing. I think I removed the bolt a while back by mistake thinking that's how to get the accessory pulley and didn't torque it down properly (it isn't oiled so I know there's a problem somewhere, that's the only part of my engine that doesn't have oil on it, LOL.

Assuming everything works, I'm going to look for the clutched alternator pulley and see about getting that installed to make life a little better for the COG as well.

It’s actually pretty common for people to remove it thinking that’s how the harmonic balancer comes off, don’t feel bad. It’s how we learn sometimes.

The bolt is a stretch bolt or “Torque to Yield”, which means it deforms once tightened to spec, so it can’t be re-used. It’s also why it’s important for the correct torque procedure and value to be used.

Fortunately connected with a guru to see if this is the issue on my 96. Gonna trailer the car over tomorrow. Is there any way to get the pics from the first posts in '011?

You may have to reach out to Frank on another forum. He doesn't have this TDI anymore and I doubt he continues to monitor this forum. Try messaging him on vwvortex, I know he's still active there under the same handle.

Pics updated