Figured out why my timing belt broke

Crank bolt backed out. As far as I know, its never been removed since it was assembled at the factory. I had about 265k miles when this happened. Did I remember hearing VW increased the torque on this bolt with the PD engines? Mine is a 2002 ALH.

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Looks like a stress crack on the crankshaft pulley as well

Yes. This happened at idle. Should I be concerned that the engine ran a few seconds without the damper connected?

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So the damper separated from the pulley and for a period of time it was running until it lost time and crashed?

Is the concern the head is ruined? Piston projection needs to be checked too if it was running.

Well the pulley and damper came off as a unit since the bolt backed out. I do have valve impact, and am in the process of removing the head. I was wondering if there could be any issues with the crank bearings from running a few seconds with no damper.

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It's an interference engine, so if the engine was turning at all when the timing belt came loose pistons met valves.

The damage may be a few valves and lifters or the bottom end as well; head has to come off either way.

EDIT: OP is a faster typist than me.

I asked because you wondered about the motor running without the damper present. So the pulley and the damper came off as a unit and it crashed.

Coasty said:

Well the pulley and damper came off as a unit since the bolt backed out. I do have valve impact, and am in the process of removing the head. I was wondering if there could be any issues with the crank bearings from running a few seconds with no damper.

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zslnk said:

I asked because you wondered about the motor running without the damper present. So the pulley and the damper came off as a unit and it crashed.

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Yes. Actually the timing belt didn't actually break, just skipped off the sprocket when it came off.

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Coasty said:

I was wondering if there could be any issues with the crank bearings from running a few seconds with no damper.

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Fair question. The crank bearings are pretty robust and the damper's mostly about vibration reduction, so the bearings are probably the least of your worries, unfortunately.

Yes, the bearings would be fine from running without that dampening. However, gotta wonder what happened to crack the pulley and eject the bolt, Enough force could damage the crankshaft.

Can you post a pic from the top? Is the crack in line with one of the balancer bolts?

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WildChild80 said:

Can you post a pic from the top? Is the crack in line with one of the balancer bolts?

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Loiks like no. The crack is on the bottom, not in line with a damper bolt.

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The damper is to protect the crankshaft from a torsional resonance that will break it. The failure you describe is not going to put the crank or its bearings at risk from a wee bit run with no damper. There is of course risk to darn near anything else; valves, lifters, rods...as the crash forces are not at all small.
cheers,
Douglas
best o' luck getting it back together and happy.

Coasty said:

Yes. This happened at idle. Should I be concerned that the engine ran a few seconds without the damper connected?

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The very second the pulley loosened the IP would stop turning, too. No IP, no engine.
The only force acting on the valves and lifters would be residual energy from the
flywheel and rotating mass. At idle this would not be very great. So that's good.
I would remove the valve cover and look closely at the lifters and cam. It sounds
like you're already doing this. Any evidence of damage means a head rebuild.

Yes, definitely valve damage. I can see spider cracking on two lifters. Head is nearly off...

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I would be surprised if you need more than a cam, lifters and a few valves.
In other words I'd guess the bottom end is fine but check protrusion anyway.

I'll look and see if I can find the piece you need, I had an engine that seemed to have a thermal and oil starvation issue. If I can find it I'll send it to you for cost of shipping

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I just went through this with a car that had uneven compression. It started well but 'unevenly' in the winter. The compression numbers had about a 60psi spread from high to low. The motor was replaced for another reason. The motor I found had destroyed a lifter and although the valve spring and keeper was intact, the piston did contact the valve at some point (lifter debris) before it closed and stayed closed. I checked the protrusion on this one and it was uniform. I put my old head on this block and got 495psi x4. It starts very quickly and uniformly.

The motor that I replaced showed evidence of the head being off before (cleaning scratches on head gasket surface). I suspect that the old motor had a timing belt event and they put a new head on it. When I saw this, I checked the piston protrusion and the lowest compression cylinder had a slightly bent rod. I forget the numbers but it was perhaps 0.005" lower. It ran well and the mileage was fantastic but cold starts were not great.

WildChild80 said:

I'll look and see if I can find the piece you need, I had an engine that seemed to have a thermal and oil starvation issue. If I can find it I'll send it to you for cost of shipping

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I appreciate that very much, but I just purchased one. Hopefully no rod damage for me!

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Coasty said:

I appreciate that very much, but I just purchased one. Hopefully no rod damage for me!

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Something like that it seems like a new one would be in order especially after what happened.

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