Timing Belt Blues

[BimMeUp]

I was wondering if anyone could tell me what could cause the teeth on the timing belt to break off. The belt itself did not break, just the inner teeth. Also, will I need to get a whole new cylinder head, or just pistons and valves?

Thanks

P.S.
Forgot to mention, the car is an '84 528e. Also, anyone know what would cause my heater fuse to melt when I have the radio on along with the heater, cooling, or A/C??

Thanks again.

[Dark Helmet]

depends.... I don't think the super-etas are interfeerence motors, but maybe they are... an old belt can do that, I've seen it more than once, it just becomes brittle and breaks, contamination can also speed this process.

if it IS an interference motor, and you're handy with tools, its less outright money to get a salvaged motor.... but you've got to be better than I am with this stuff (or just crazier) as its quite an undertaking.

[88m53453]

Definitely an interference motor, the teeth on the belt usually strip off vs the belt breaking, very rarely do I see a belt broken at my shop

[Dark Helmet]

I've never seen an M20 belt break... but some japanese motors, I have....