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flywheel pulleys come off??

3K views 7 replies 4 participants last post by  leeandstaz 
#1 ·
Fixed up my k4m megane 1.6 16valve yesterday and had it running sweet as a nut, one problem i forgot to tighten up the crank pulley and it cam loose the car stopped and would just turn over real fast.
Now can i expect more valves to be bent? and another gut load of work?
Cheers.
 
#2 ·
yup, bent valve stems, rocker arms, broken tappet covers.
the camshaft locking pins will be busted(if it even has any), possibly even bent camshafts, definatly damaged lobes on the camshaft.
hopefully the pistons wont be cracked, scorred most probably.

worst case the head may be warped, all the head bolts are ready for the bin regardless.

it all depends on how much clearance there is between the piston crown and the valves when fully extended, you might be lucky, some crowns are shaped enough to allow valve extension without impacting(not common though).

you will also need to strip it right down and check all the bearing shells on the piston rods/crankshaft :(

i really dont envy you new project.
though on the bright side, there are plenty of breakers yards you can get bits from.

maybe cheaper to just get another engine for £150+shipping/vat

best of luck
 
#3 ·
Hi Mord,
Thanks for your reply.
Ill explain a bit more about the situation, As some of what you've said makes sense and some doesn't.

I bought the car about 4 weeks ago off a chap who had been going down the M5 at about 70Mph when the cambelt snapped.
When i got the car home i stripped the cylinder head down and the only suspect parts were 12 bent valves, And a few minor marks on the piston (Nothing major).
So i cant see how driving along my estate at 15 - 20 Mph will cause any more damage than when the belt orginally snapped at 70mph.
The pulley didnt come right off, Just away from the crank, So i take it the cams were turning but the Crank wasn't.
Do you know what locks the floating crank pulley to the Crank, Is it the tension of the pulley being bolted to it? Which then allows the Crank to be engaged so the crank and belt pulley are working together?

:devil::devil::devil:
Cheers, Lee.
 
#4 ·
Lee,

Yes I agree that mord is being somewhat of a doom merchant in his diagnosis and camshaft damage is most unlikely; similar damage to the first time is likely (bent valves). There is nothing to key the camshaft pulley to the crankshaft; it relies on the aux belt pulley being tight to stop it slipping. The bolt holding the aux belt pulley is a stretch bolt so should in theory be replaced every time it is removed (as should the head bolts for the same reason) - I've never bothered on my own car (I'm sure someone will tell me it's bad practice and I won't argue the point - it's up to you but if I were doing the job on someone elses car I would bother). At the very least, it's important to torque the bolt up correctly. Similarly the camshaft pulleys aren't keyed and have to be done up extremely tight as a result - but having just taken it apart, I expect you already know all this - at least you won't make the same mistake twice :)
 
#5 ·
Hi Stevewes
Thank you for your reply, Surely its common sense that if the belt snapped at 70mph and the damage was only 12 bent valves then at only 15-20 mph it couldnt be any worse (Bearing in mind that Mord didnt have all this info before he replied - which i am greatful of).
But i have got some second hand valves now along with lifters and followers from a K4M at my local breakers.
I DO ALWAYS replace the cylinder head bolts no matter what the car as its always better to be safe than sorry.
But what i wasn't aware of was that the Crank pully bolt was a Stretch bolt.
So like you said to make sure i dont make the same mistake twice i will be relacing that one too and tourqing it up correctly!!!
Does anyone know what the tightening settings are for the AUX belt pulley?

Thanks all so far! :cool:
 
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