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

"MW de Jager" > wrote in message
...
> 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?

I would suggest it was either fitted incorrectly, or, less likely IMO, the
belt was faulty.
Mike.

"MW de Jager" > wrote in message
...
> 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.



Of course there is no compression, the belt is broken and the valves are in
various combinations of being open.

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

"MW de Jager" > wrote in message
...
> 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
>

MW de Jager wrote:
> 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?

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.

> 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

Expected with the cam sitting idle and may be hard on pistons and valves
if they are colliding in the process...

Cheers, Bob

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?

> 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?

Did you fit a new tensioner at the same time?

--
Who needs a life when you've got Unix? :-)
Email: , John G.Burns B.Eng, Bonny Scotland
Web : http://www.unixnerd.demon.co.uk - The Ultimate BMW Homepage!
Need Sun or HP Unix kit? http://www.unixnerd.demon.co.uk/unix.html

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)


--
jmno
------------------------------------------------------------------------
jmno's Profile: http://www.usenetcars.com/member.php?userid=2905
View this thread: http://www.usenetcars.com/showthread.php?t=393342

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


"jmno" > wrote in message
...
>
> 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)
>
>
> --
> jmno
> ------------------------------------------------------------------------
> jmno's Profile: http://www.usenetcars.com/member.php?userid=2905
> View this thread: http://www.usenetcars.com/showthread.php?t=393342
>

..
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

"MW de Jager" > wrote in message
...
> 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
>
>
> "jmno" > wrote in message
> ...
>>
>> 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)
>>
>>
>> --
>> jmno
>> ------------------------------------------------------------------------
>> jmno's Profile: http://www.usenetcars.com/member.php?userid=2905
>> View this thread: http://www.usenetcars.com/showthread.php?t=393342
>>
>
>