Anyone else have a crank bolt shear off?

I have been having some issues with my tdi loosing time so I narrowed it down to the crank sprocket. I bought a new crank sprocket and pinned the crank because the 'keyway' was all chewed up. Things went well for a few weeks till last night when the car just died as I was driving it. I thought I did something stupid to kill it so I turned it off and tried to start it again. Nothing.

Pulled over to the side of the road and popped the hood. Looking down i saw my pully and crank sprocket sitting sideways. Reached underneath the car and pulled the crank bolt out of the center of the sprocket. It had sheared off while driving.

Has anyone had this happen to them before? I tightened the bold down right. Even left some gap in the legnth of the pins so it could pull the sprocket down onto the cam with out hitting the shoulder on the bolt.

Going to pull the head in a bit and see how many bent valves I have and try to get the rest of the bolt out.

To prevent the assumption...did you replace the bolt, or reuse it?

They are one-time use.

Tony

When you mean right, I am assuming you mean a New bolt, with lightly oil lubed threads & collar, torqued to 66 ft-lbs, then 90° from that? (it's VERY tight)

Just checking here to make sure we're on the same page by defining what is 'right'.

If that is the case, then no, I have not seen it.

How was the crank snout face when you put the sprocket on? Was it resurfaced and completely flat (you mentioned having to pin it).

Yea, new bolt. And yea torqued to spec then a quarter turn. I followed G60ING's guide on it just to be sure I did it right. Took my time and made sure the crank snout was nice and smooth before I installed the crank.

It just kind of has me baffled. Its a thick bolt and would take a hell of a lot of force to twist it off especially with two 3/16" pins in it.

Got pictures of the bolt? Prefereably in profile and looking at the end that failed. Looking for a little failure analysis. Did it fail in shear, tension, torsion, etc.

Tony

Damn, sorry to hear that. Definitely let us know what you find out, I'm curious.

Whose bolt is it and from where did you buy it? I'm now wondering if you got one of the repackaged Chinese Specials I've heard are cropping up, where reputable vendors are left unaware they are getting junk parts in name-brand boxes. Nothing concrete I've heard, but there seem to be a rash of stuff like this going on lately.

If you can find the source of the bolt, and know the manufacturer, contact them to see if they'll analyze why it failed...unless there is a member on here that can do the same thing.

If something like that happened costing me thousands of $$$, I'd want to know everything about that bolt, right down to what the guy on the assembly line had for lunch.

I do failure analyses as part of my business. A broken bolt in a case like this is most often caused by relative motion between the assembled parts. Bolt then flexes as assembly rotates and fails in fatigue.

Something not fitting up right, clamping force from bolt somehow inadequate, too much clearance in fitup, buggered threads, radial loads too high, etc, etc.

With enough clamping force, even a poor fitting assembly can remain rigid and live.

Revisit the whole thing and how each piece fits.

Yup, where the bolt came from might be good info to know in this case...there's OEM and then there's "OEM or equivalent."

I'm pretty sure it is a febi Bilstein bolt. I got it from one of my suppliers and the crank sprocket is a Meyle. I'll try to get pics later. I looked for the bolt when i was loading the car and couldn't find it, so I stuck it somewhere. That too pisses me off. Pics later if I can find it.

Maybe have Ski look at it when you find it, sounds like he may be able to help.

I just had this happen to me... apparently, it's my third time in the last few years after looking at maintenance logs for the car from the previous owner. I've got this sinking feeling about this like I somehow can't get out of it. The money is one thing, having it happen again soon is another...

I've already bought everything to put the car back together as well as a new harmonic balancer. The last crank bolt used was a Febi bolt (Febi #054 54051 280 or N905 771 01). This time I bought the crank bolt new from a dealer.

Does anyone else have any info on this? I don't think I can stomach going through this again and am even thinking about backing out of this repair and just finding another vehicle. The only other thing I can get from research is that the crankshaft could be cracked or bent or one of the crankshaft bearings damaged.

h.ubk

So, I have done a lot of research on this issue. Here is what I have come up with:

- I called ARP and their closest crankshaft bolt is 3mm short and comes with a washer that takes off a bit more length, so that is out.
- I have ordered the ARP UltraLube engine assembly which should ensure the bolt is properly tensioned when it goes in.

However, that doesn't entirely solve the issue at least from the research I have done. There appear to be a number of people who have experienced this issue who know what they are doing (i.e. how to torque the bolt, not reusing it, etc.). It also appears this happens on higher mileage engines -- i.e. way past warranty period and some of the people who experience it probably don't bother trying to figure it out or fix it.

The previous owner used Febi bolts and I am using an OEM bolt, but I have not been able to find any other aftermarket bolts anywhere, suggesting that Febi is likely the OEM. I would rather pay the extra few bucks to get the OEM bolt just in case, but I don't think this can be written off as just an inferior quality bolt.

The research I have seen points to the keyway on the crankshaft getting damaged over time. One fix is to remachine the crankshaft and weld something onto the keyway. I believe ACME sells a kit for this. Some of the UK threads indicate there are shops that can do this with the crankshaft in place, but I wouldn't know where I could have that done.

From ACME (http://www.acmeadapters.com/faq.php):

What is the concern about the VW 1.9TD engine common crank pulley failure?
The 1.9TD engines have an issue with the bottom crank pulley coming off the engine during operation. This happens because the keyway at the nose of the crankshaft wears allowing the crank pulley to move and oscillate. This movement eventually leads to crank bolt failure causing your harmonic balancer and crank pulley to come off during engine operation. Because the VW diesel is an interference engine, this usually results in bent valves and expensive head and or piston repair. Should you decide to run a 1.9TD (AAZ) engine in your application, ACME highly recommends modification to your 1.9TD crankshaft by welding up the keyway and machining the end of the crank to a "D" shape. This will allow you to use a later model TDI crank pulley eliminating the possibility of a future failure. Contact ACME if you need a crankshaft modificaiton kit for your 1.9TD (AAZ) engine.

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If the keyway is at fault, it really doesn't matter how tight the bolt is torqued or stretched or whether the bolt was installed wet or dry because the vibration of the crankshaft + the road vibration will introduce micro-cracks in the bolt and eventually break it in half. I cannot think of a way to test this in operation, although it would seem to be the likely culprit if your keyway is marred and you keep eating through crank bolts.

Here is a writeup with all of the engineering details:
http://www.utterpower.com/vw’s-1-9-td-problem-and-solution/

Another solution I have seen is people cutting holes in the crankshaft and fitting with dowels to match with the crank pulley gear to reduce the vibration.

Here are some of these threads:

http://forums.vwvortex.com/showthread.php?1598023-Here-is-my-complete-Crank-Fix
http://forums.tdiclub.com/showthread.php?t=318602
http://clubgti.com/showthread.php?185176-g60-crank-pulley-dowel-fix

Some of these appear to be focused on building higher performance engines and older VW diesel engines, but the concept appears to be the same.

Has anyone been through one of these fixes on a 1Z/AHU engine and put a lot of miles on it? At this point, I would be happy to change out the crank bolt every time I do a timing belt change if I can get 60,000 miles on it.

h.ubk

Can't remember for sure, but if the bolt is supposed to be installed dry it will get over-torqued if you use assembly lube. The Bentley will mention if assembly lube is to be used.

One question: does your alternator have the clutched pulley installed, and, if so, is it working properly?

Besides the crank snout redesign adding the clutched alternator pulley was probably the single most effective engineering change VW made to reduce crank bolt problems.

That ACME kit doesn't apply to your engine. The older AAZ pulleys had a 1cm (-ish) keyway, while your 1Z already has the full "D" shape the kit aims to provide.

Can't remember for sure, but if the bolt is supposed to be installed dry it will get over-torqued if you use assembly lube. The Bentley will mention if assembly lube is to be used.

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First of all, I'm pretty sure the last guy dry torqued it all three times. It had locktite on it. I doubt it would be a dry torque spec. The value being measured is really tension or clamping force. With dry torque, 85% of the force is not being applied to stretching the bolt, but dissipating as heat. There are also potential variables in tension even when using the same torque on the bolt. I've seen this debate here and the fact that a lot of people are bolting it in wet and not having problems tells me this is likely the better way to go.

There doesn't appear to be an easy way to check the tension on the bolt once it is installed, but one guide mentioned that properly tensioned, the bolt should only be movable with a 3/4" breaker bar, thus a reasonable test would be to use 1/2" tools and if it can be loosened, then it is already too loose.

One question: does your alternator have the clutched pulley installed, and, if so, is it working properly?

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I am not sure. Is there any way to visually ID them?

h.ubk

h.ubk said:

First of all,

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Doesn't sound like you wanna hear this, but the Factory Service manual says (page 13a-4):

"All threads and shoulder contact surfaces must be free from oil and grease. DO NOT oil threads".

The factory tightening proceedure will have been designed with that criterion in mind.

So, and just my opinion, but if it has locktite on it was done "wrong". For starters, locktite would wet it a bit.

I'd also say that if many people wet it and had no issues, and lots of us run it dry and have no issues, I struggle with the need to re-engineer it or pin it or replace the OEM bolt with something else.

But, your car your rules.

In terms of the pulley, probably the easiest way to tell: the solid one is held on by a standard nut and washer, the clutched one by a internally-splined fastener.

I don't have access to the FSM, but one of the threads shows the following:

The 1Z/AHU specifies to lubricate the threads and under the head flange of the crank sprocket bolt.
The ALH specifies to NOT lubricate...
Same 90 Nm / 66 lb*ft, same 90 degrees additional.

Go figure.

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Applying the bolt dry will result in a lot of variables in tension. If VW's guidance was the bible, I doubt this problem would exist in the first place.

What FSM for what engine are you looking at?

h.ubk

There's a huge difference in feel as this bolt is torqued or loosened between an oiled and dry installation. Oiled is smooth, progressive torque increase/decrease while dry is "crack-crack-crack" and jerky. I removed a crank bolt 8 years after I had installed it oiled and it was just as smooth and progressive loosening as it was tightening up.

Another potential issue with these is if the counterholding provision on the crank sprocket is not that rigid and there is some flex/movement, I wouldn't have complete confidence in the resulting torque/bolt stretch.

Measuring tension is best done by measuring the bolt stretch. It would be interesting to see if we remove crank bolts by those done wet/dry and see which ones are fully stretched...

h.ubk

The shoulder and threads on the 1Z/AHU bolt get lubricated with a light coating of oil, this is as per the Bentley. I've done a bunch of these and the only ones I've had an issue with is revkev's, which was screwed up from a Trusted Mechanic on here. I suspect the crank threads were damaged when the old bolt was reinstalled and dry. I used two forms of Loctite on it and it lasted 5 years but just had to be done again due to the start of movement. All the rest are still perfect.

I just changed out the crank bolt and pulley on my 97 Passat (1z) last fall as suggested PM to keep the car going as it has 230xxx miles. To my knowledge that was the first time. Definitely recall the D shape on the end of the crankshaft that the pulley sits in. I do not recall a key but that doesn't mean anything. Also recall that the info I had researched said to lightly oil the threads, which I did. The old pulley looked absolutely fine and am beginning to wonder if changing it out was a wasted effort. Maybe should have left it alone?

I think the issue is that the bolt could end up backing itself out over time and then you would be where I am right now -- a new or rebuilt head and valves or possibly worse. The bolt is a one-time use, so it's pretty difficult to see what the torque is. I'm planning to try to turn mine with a 1/2" socket when it is done to check it. If I can turn it in either direction, that would mean it is too loose.

h.ubk

Jumping on this thread. Have an AAZ in vanagon I just got. Was really pumped about it. 28mpg on the highway etc. But I see wobbling in the crank pulley and my heart sank after reading more and more about the engine, and finding this issue. Good news is its parked out front and nothing has broken yet. Bad news is, I have to spend more money on it that isn't something cool for camping, like diesel furnace, or aux battery and solar panel..hahaha. Anyway, trying to figure out how far I need to go. Seems like the machining and welding fix is the best bet. I've read that they updated the engine with the new D shaped crank as opposed to key, and also a new and stronger crank bolt, and the clutched alternator pulley. If I already have wobble, then the key is worn. Can I get away with updated new crank bolt, new pulley and clutched alternator pulley? Not sure where or by who i can get the crank nose machined....

Unfortunately you won't know till you pull it apart and inspect the crank nose.

The sprocket generally wears faster than the crank nose, so you may just have to buy a new sprocket and bolt.

All depends on how long the two have been rocking back and forth.

Ok, that's good to know. Will order the parts and take a look. Thankful for all the diesel enthusiasts! This forum has been great for me and learning about and maintaining my jetta, that I've had for 11 years now. New to the AAZ and the vanagons.

Another thing I’m trying to figure out is the parts. Anyone have the OEM part numbers for these fix parts? Guess I need another Bentley...

One thing I would mention is to pull the bolt out entirely and make sure it is clean and lubed before putting it in. I know some people say to put it in dry and the FSM says that, but if you do your research on the engineering involved, that is 100% wrong. Most people do not understand the difference between torque and tension so you will see the same answers parroted again and again. Installing it dry causes most of the torque put on the bolt to dissipate as heat and does not allow the bolt to stretch to the length it needs for full tension.

My belief at this point is that the PO on my car put it in dry twice and that is why it failed. If you pull the bolt out, replace it with a new one. Do NOT reuse it. I have seen these bolts on eBay selling being sold used. That is just idiotic and will contribute to this problem in additional cars.

I do not belief right now anything else needs to be done to it. I have put 5K miles on it so far and am keeping an eye on the tension of the bolt once a year. If I start to see it getting visibly looser, I will update this thread here.

h.ubk

The alternator decoupler pulley was Gates 37010P.

The harmonic balancer was 028105243T.

I don't have the crank bolt details, but you should be able to get it at https://www.oemvolkswagenparts.us.

That is what I ordered for my 1997 Jetta Tdi. Don't bother with the Bentley. It's nearly worthless, except to provide meaningless details on other variants of Volkswagen cars.

h.ubk

And that's the keyed balancer? Right now I don't plan to do the D cut on the crank. Pricey... I used to use 1stvwparts but your link was $20 cheaper. Thanks!

I think the cornfusion about the oiled/dry installation is that the AHU bolt is lubed. The ALH goes in dry.

I don't know about the keyed version.