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The big thing however is crank keyway failure when going with the serpentine setup. If you're building the motor fresh and want to use the serpentine stuff then you need to get your crank machined for the TDI style crank pulley - it's not expensive especially if the crank is out of the block still. You also need to make sure the alternator you're using has the clutched-style pulley. When the 1.9 TD's came out with their serpentine setup originally they had a lot of problems with the drive pulley (and timing belt pulley) getting broken off the nose of the crank, which results in no timing belt, which turns in to a mess.
What year TDI's with the serpentine setup had this problem and what was the fix? Did it turn into a recall?
It was the 1.9 IDI's that had the problem, they redesigned the crank snout and the timing pulley on the TDIs so it doesn't use a keyway anymore, presumably to fix this very problem. As far as I know all TDI motors have the fix applied from the factory (combination of the redesigned snout and the clutched alternator pulley).
The issue apparently is that the serpentine belt setup is more efficient at transmitting force than the V-belts were. The power output of a piston engine comes in "pulses" as each piston fires, it's not smooth and continuous. On a diesel it's particularly bumpy due to the force required to push the piston back up the bore with a diesel's high compression ratio.
With V-belts the belt system would soak up a lot of the "pulses" - the belts will dig deeper in to their pulleys, etc. Serpentine belt drives however are just more efficient, so that "pulses" are transmitted to all the accessories around the engine such as the water pump, PS pump and alternator. The alternator has a fairly large spinning mass internally which wants to keep going at a constant speed.
The crank pulley on the 1.6IDI's and 1.9IDI's has a center bolt and a woodruf key which engages into the pulley. On the 1.6 it wasn't an issue since they only ever came with V-belts. But on the 1.9 IDI with its serpentine belt set up that poor woodruf key would be getting smashed one way due to the alternator first resisting the acceleration of the belt as a piston would fire, and then smashed back the other way as the engine would slow down slightly due to the next piston getting close to the top of its compression stroke and the alternator wanting to keep spinning at its now-accelerated speed. Eventually the woodruf key starts getting loose, the nose of the crank starts getting chewed up and then the crank bolt starts coming loose, then the whole pulley would come off or even just bend enough to let the timing belt slip. Boom, smashed engine.
That's why there's 2 parts to the fix - #1 is eliminate the woodruf key by changing the shape of the crank snout to a "D" shape, and then using a pulley with a corresponding recess - as far as I know all TDI's have this fix. #2 is to eliminate the "backwards" force from the alternator by using a clutched pulley. It gives the alternator the ability to keep spinning at a constant speed rather than being sped up and slowed down during each compression / combustion cycle.
I don't know if there was ever a recall - from what I've read around here it was the kind of thing that tended to happen after a car would have been out of warranty. Presumably that's what happened to my Jetta with its previous owner, which is how it ended up with a 1.6 in it instead...
Topic: gas to diesel swap?? (Read 6399 times)
