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Crank sprocket damage :(
by
TD_vento
on 22 Jun, 2005 20:58
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My first post in this forums starts by addressing this problem. Its the second time that the pulley on the crank gets worn out. The crank itself is also damaged and you get the usual vibration which has caused the power steering bracket to brake off.
I read somewhere that there is a new bolt for the crank pulley.
Im wondering if there are any techniques to try and fix the problem without removing the crank. Its one of the most annoying problem you can have, has happened to my G60 aswell.
Im am wondering if i should just get a second hand crank and have the machine shop balance it and put it in the block? I dont think machinig the damaged crank would be as good as another good crank. The crank sprocket isnt that bad its usually the pulley that gets worn more due to the crank being forged.
Is that crank bolt strechable? I reused it on the last pulley change which makes me think why has caused it again.
Im sure some of you have expereinced this problem so any opinions are welcome.
thanks
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#1
by
desertwilow
on 23 Jun, 2005 08:22
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the problem seems to be the keyway is not big enough. some use a stretch bolt some do not. you can find out by checking your bentley, it will tell you to replace the bolt if it is. the vanagon bentley even shows the new replacement sprocket and 14 mm bolt. my vw guy said the way he deals with a bad crank keyway is to machine it. i took a photo of mine and showed it to him. thank the vw god he said a could get away with a little filing and thread locking the crap out of it. good luck
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#2
by
TD_vento
on 23 Jun, 2005 10:10
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Well i have removed the gearbox today and tomorrow will be able to lift the engine up, i think even if they machine it it will still not spin 100% straight such a ***ing horrible job to be under the car in this hot day :x
I have found a crank at breakers, will take it to the engine shop to get it measured compare it to the old crank see if i can use the same bearings.
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#3
by
asau
on 23 Jun, 2005 12:14
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good luck i am have the same problem on my aaz and am having a hard tiem finding a tdi crank and timing sprocket to replace mine
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#4
by
QuickTD
on 23 Jun, 2005 12:54
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I would have the crank welded up and machined to take the TDI style pulley. The problem stems from the inadequate drive key in the AAZ crank. The TDI pulley has a flat side on the crank instead of a key. I would never dream of replacing an AAZ crank with another AAZ crank, it is well known that the AAZ setup doesn't last long. A welded and machined crank (at least if I do it) is far better than stock because I take the time to measure and fit the end of the crank to the new pulley. I always make it a nice press fit. If you really feel you must use another stock crank, the TDI crank and pulley will bolt right in, just ignore the crank sensor wheel.
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#5
by
TD_vento
on 23 Jun, 2005 13:32
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Im not familiar with the tdi crank and pulley, what exaclty do you modify? Some pics would help.
thanks
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#6
by
QuickTD
on 23 Jun, 2005 16:36
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I don't have any pics, nor do i have any parts lying around to takes pics of right at the moment. I'll do my best to describe the difference between the TD and TDI cranks.
The TD and TDI cranks are identical in all bearing diameters and in the diameter and length of the stub where the timing pulley mounts. You are familiar with the method used to "key" the timing pulley to the crank on the AAZ, the TDI uses a slightly different method. In place of the small keyway used on the AAZ crank there is a flat machined across one side of the pulley stub of the TDI crank, making it "D" shaped when viewed from the end. The pulley has a corresponding flat. This setup has proven to be far more durable than the tiny key used in the AAZ.
When I repair these cranks I first TIG weld the worn crank nose, filling in the old worn keyway completely using alloy steel welding rod and building up the worn outer diameter and end face. I then place the crank in a lathe and machine the welded area down to the proper diameter to achieve a press fit in the bore of the new pulley. I also machine the the end of the stub slightly concave to assure that the pulley will cannot rock about the centre bolt. The crank is then placed in a milling machine and the "flat" is machined onto the side of the pulley stub in the stock location. Again, the flat is machined such that it will be a slight press fit when the pulley is installed.
When the engine is reassembled you must use a new bolt and torque it to spec (66ft/lbs +90º). I would also recommend getting a one way clutch alternator pulley from a TDI. The one way clutch prevents the alternator from backdriving the crank when the crank speed is rapidly changing (as it is when the engine is idling). This helps prevent the pulley from working loose again.
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#7
by
TD_vento
on 24 Jun, 2005 09:58
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Ok this makes it clear now, and the alternator clutch pulley is also a plus. What i done today is removed the worn pulley out, i found out that the bolt was almost loose. I still havent removed the gearbox or the engine. What i done is with a small file i slowly flatened the face of the crank flat area where the pulley meet it, it was very unflat causing the pulley not to lay flat and making it possible when the pulley is mounted to create slack due to the uneven bumps changin shape. I spent about 3 hours and got it as flat as possible, while doing this i got an idea. I was thinking about creating a second key 180 degree from the original. I was thinking about cutting a channel in the crank and do the same to they new pulley by using the same depth and lengths. In there install the key, i need to find a key though. I think i can get away this way without removing the crank. The second key would give it more stability, i might even put 2 keys at 120 degrees each one. As long as the pulley will lay flat on the crank and they keys fit tight i think this would work. What year did this alternator pulley come in TDI's?
thanks