E30 cambelt broke - why

My wife's E30 320i broke its cambelt again. This time it's not my fault. The last cambelt was replaced a mere 18,000km (11,000 miles) ago. Why would
it break the (new) cambelt?
The cylinder head overhaul is probably going to cost me an arm and a leg, cause it has no compression if you turn the engine over.
MW
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I would suggest it was either fitted incorrectly, or, less likely IMO, the belt was faulty. Mike.
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Could be the tensioner also, did you replace it with the belt?
-Russ.
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Of course there is no compression, the belt is broken and the valves are in various combinations of being open.
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If you keep the car outside and subject to extreme temperature variations the cambelt (and lots of other parts) don't last as long as normal. It would probably be cheaper for you to get a replacement head off a wreck (about US$100?) and stick that on with new gasket kit (and cambelt) rather than get it all reconditioned.
Steve

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MW de Jager wrote:

I am shooting in the dark here, you mention that it was 18,000 km ago but do not give an indication of time from the last replacement. I understand that timing belt replacement is recommended every 3 years or 80,000 km. Depending only upon distance driven is not a great idea with belt replacements.

Expected with the cam sitting idle and may be hard on pistons and valves if they are colliding in the process...
Cheers, Bob
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What is the condition of your water pump? Is there an oil leak inside of timingbelt cover compromising the timing belt itself?Have you had the head milled? Possible bad bearing in the camshaft causing binding!Did you set tension to the timing belt exactly to specifications?Too much tension will cause premature failure! Did you reuse the tensioner or did you replace as recommended?
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Did you fit a new tensioner at the same time?
--
Who needs a life when you've got Unix? :-)
Email: snipped-for-privacy@unixnerd.demon.co.uk, John G.Burns B.Eng, Bonny Scotland
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have a close look at the broken belt. is it contaminated with oil/water. was it snagging/rubbing off any adjacent fixed parts. possible migrated bolt/nut ect, check sprockets for damage. more than likely incorrect tension. fit a new belt and turn engine by hand, you will soon know if there are any damaged valves.(you may be lucky)
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The last belt was fitted 18months ago and a new water pump was fitted just before that. A 2nd hand cam pulley (crank side) was fitted because the previous belt was damaged on the front (radiator side), and the pulley showed wear. I'm sure the cambelt tensioner was not replaced. I'll make sure it is replaced this time. The mechanic said that the belt runs pretty close (teeth almost touching in places) but everything was set to spec as far as I know.
My wife said she heard noises from the front, of things breaking and she was going at 130km/h at the time. The last time this happened I was in 3rd at 40km/h - 4valves were bent 3 rockers broken, so I'm sure there is going to be a few broken parts apart from the belt.
My mechanic can only look at it on Monday to determine the damage. The cost of a 2nd hand cylinder head is ZAR 2,500 = US$ 370 = GBP 210 I'll have to compare this to whatever they quote for the cylinder head reapair. If I buy a 2nd hand head, do I need to have it skimmed before fitting?
Thanks again for everyone's input.
MW

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. You might be able to salvage some valves and the camshaft (and the head itself) but I suspect a complete replacement head would be much quicker and cheaper than messing around with the old one. As long as your pistons don't actually have holes in them from the valves smashing into them at a zillion miles an hour they should be ok too. Yank the old head off first so you can make sure the bores aren't badly scored from any broken bits of metal you might find in there, because if they are you'd be best to replace the whole motor (which will at least save you the cost of a head kit). If you get a replacement head you should check and see that it's not too warped and especially not pitted. BMW say to resurface the head if it's got more than 0.1mm bend but I've gotten away with 0.5mm just by over-tightening the middle head-studs like any cowboy would and with no ill effects. Best of luck,
Steve

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