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.
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