stripped timing pulley

[moTthediesel]

Well, I finally got around to tearing down my wrecked 1.6TD engine from September. At that time I thought I'd broken the crank, though I was told by all here that's unlikely. The symptoms were that in had somehow gotten out of time without breaking the T belt and had had a valve crash, destroying the head. The odd thing was, it would crank as normal with the starter, but the timing end of the engine would not turn at all  

As it turns out, what happened is that the formed key in the crank timing pulley simply sheared off!



The break is very clean, with almost no damage done to the keyway in the crank. I was still developing the engine install (in my 356 coupe) at the time, so I was looking at the engine running every day, and never noticed any wobble in the lower pulley.

I know that this is a common problem in the 1.9 engines, but I wonder -- this was a Quantum engine and it has a very heavy cast cap type vibration dampener, not like the simple stamped unit on my 1.6 NA engines. Is that similar to the kind that gives trouble on the AAZ engines?

I guess I should re-engineer my drive belt system to the one belt type that's on my '84 Golf. As I don't need the AC compressor drive or the power steering pump anyway, it's back to the old KISS principle for me  

[moTthediesel]

With any damage like that I always think, 'which came first, the chicken or the egg?'.  If the crank bolt was correctly torqued, it's extremely unlikely that the key would simply sheer like that unless there was an extreme flaw in the metal.  Much more likely is that something stopped the cam from turning (e.g. stuck valve or piston/valve contact) and the tension on the timing belt stripped the sprocket.

Yeah, I'd tend to agree with that --- so maybe the belt jumped a few teeth (unlikely, but possible) or the cam timing sprocket spun?

I had just built the engine (it didn't have 500 miles on it) and it was all torqued to spec with new bolts. The last day I drove it, it ran a little hot on water temp (about +10F), but the egt's were also up about 100F from normal, so being out of time is a definite possibility, but how did it get that way I wonder?

There have been many (MANY!) cases of valves and pistons coming together in these engines, but have you ever seen it result in sheering that key like that? 

[theman53]

I know KISS , but this is what I would like to do for mine.

http://forums.vwvortex.com/zeropost?cmd=tshow&id=3793002

[Rabbit on Roids]

that dowel pin setup looks like you could run some power off the front pulley now.. like im thinkin, oh, supercharger maybe?

[Black Smokin' Diesel]

that dowel pin setup looks like you could run some power off the front pulley now.. like im thinkin, oh, supercharger maybe?

Yes but I agree with Libbybapa. The TDI crank pulley is a much easier and safer mod. More parts means more things can go wrong.

[Rabbit on Roids]

i would pin it personally. tdi crank nose setup is good, but it can still break too. why not just go the extra mile and do both? then you know it would be hell for stout.

[Rabbit on Roids]

dude, you dont have to tell me about the beetles shearing dowel pins. ive dealt with a few of them myself. first one i ever saw was our sand rail when i was about 7 years old. then we drilled it for 8 pins and worked fine. but we arent trying to dowel a flywheel here. we are talking about the timing sprocket. the flywheel transfers all of the engines power to the trans. the timing sprocket doesnt transmit anything more than what it takes to turn the cam and IP. its not like we are talking about driving the car off the crank pulley. i think either design is equally worthy. if you can break either setup, i give you props..

[veedubcanuck]

If you think that four pins can't loosen then you are mistaken.  Stock beetle flywheels were pinned with 4 pins in a similar fashion and are a common failure.  A very common upgrade on beetles is to upgrade it to 8 pins.

Ah yes.... been there...had that happen.. Never tried the 8 pin method though...

[theman53]

My only thinking was that if you don't have the crank out and access to a knee mill, broach, or CNC the pins may be the way to go. AND you could reuse the pulley that failed...but since it was probably bad metal I would get new.
 I am sure there is a way to find out how to break both setups The 4 pins came from that guy on Vortex for the supercharger and worked for him.

[theman53]

Then let me borrow your broach tool 

That is my problem I dont' want to buy a tool for over 100.00 that I would use once or twice.