loose main crank pulley bolt - Alfa Romeo Forum
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(Post Link) post #1 of 22 Old 26-09-13 Thread Starter
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loose main crank pulley bolt

pulling into carpark my 2.0 ts cut out....mcf light threw up and would not restart.
used the reader and it had p0340 camshaft sensor bank 1.
got the car home and stripped it down to initially to fit a new camshaft sensor but upon checking the aux crank pulley was wobbling slightly and found the 19mm centre bolt was loose The cambelt is still tensioned and the balancer belt is slightly loose.could the timing have slipped by the loose bottom pulley eventhough it is all still tensioned up?

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Bob.
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(Post Link) post #2 of 22 Old 26-09-13 Thread Starter
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obviously the cambelt pulley on the crank is keyed but without disturbing the cambelt i was wondering how far it could move before slipping or can't it slip?
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I don't think the crank pulley kan slip, unless the pulley or key is damaged.

I'd check the cambelt timing and tension now anyway.
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(Post Link) post #4 of 22 Old 28-09-13 Thread Starter
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Went to set the tdc and found piston not moving :-(
As suspected the key built into the pulley has sheared off.I do not know if a loose bolt giving play has caused this as the car has got full service history or if it is a weak point of the crank cam pulley itself as it is not very big.I would as a precaution on high mileage cars to get this checked as a matter of course.
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Probably taken out valves as well.
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(Post Link) post #6 of 22 Old 29-09-13 Thread Starter
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Fingers crossed gazza as once the key snapped it was not being turned by the crank therefore the camshafts etc would not be turning and no piston valve contact hopefully.
But the cam pulley key is a weak poor design especially seeing as the other two pulleys are connected and driven by this pulley I would have much more preffered all 3 pulleys being a keyed sliding fit onto the crank and then the main crank bolt fitted.
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if the crank is turning the pistons are moving up and down. if the valves don't move in conjunction with this, there will always be valve to piston contact, you can't set the valves in such a way that the pistons can turn freely.

the design was made as it is to allow the valves to be timed, if you key all pulleys you can't do that unless you fit vernier pulleys
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(Post Link) post #8 of 22 Old 01-10-13 Thread Starter
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I did not mean key the camshaft pulleys just all three crank pulleys, having all three pulleys run off the cambelt crank pulley is insane especially when because of the poor design of the key takes an awfull lot of stress cannot understand why the bottom cam pulley is not fully keyed.
I would as a precaution change this pulley every second cambelt change just to be on the safe side.
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(Post Link) post #9 of 22 Old 01-10-13 Thread Starter
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Especially seeing as this car has full dealership service history and it still occured. The mileage on the car is 105 234 mls.
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Mine's done nearly 186,000 ... so it's not a design fault but could have been damaged during a cam belt change.
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(Post Link) post #11 of 22 Old 02-10-13 Thread Starter
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That is what I have been thinking gazza as I also told them to change the variator due to it becoming noisy.I was charged for it but a couple of weeks later the diesel noise on start up was back again.Dealerships eh?
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Could be the noise returning was the pulley starting to chatter on the key perhaps, rather than variator noise? Came loose after a less-than thoroughly executed belt service??

I think the key is to locate the pulleys correctly, rather than hold them tight, that is the job of the bolt, so when it came loose, that allowed the pulleys to chatter and then break the key.

There was a shot of a V6 pulley & key on here some time back, nut wasn't properly tight and although the key didn't break, both the key and pulleys were badly worn by the thing chattering back & forth.

Hope the damage isn't too bad
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(Post Link) post #13 of 22 Old 06-10-13 Thread Starter
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Got it all back together with new parts and could now check for valve damage using a compression gauge and yeah! You guessed it no compression in all four cylinders.So strip it down again to see how many valves I need to replace while I am at it a polish and port of the head wont do any harm.
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(Post Link) post #14 of 22 Old 09-10-13 Thread Starter
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8 exhaust valves and where they hit pistons it has pinched the top compression ring which has caused a tight fit in all 4 cylinders crank is hard to turn by hand.Next hand . Next step drop sump and pistons out see if I can salvage them if not I may have to scrap a otherwise lovely car.
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If its any help we have a very good 2.0 TS 63,000 miles give Day And Whites a ring
John
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Thanks I will keep you in mind.
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(Post Link) post #17 of 22 Old 15-10-13 Thread Starter
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C'mon hands up! Who designed the sump pan on these flaming cars Aargh!! For heavens sake gearbox removal to get to the last couple of bolts!
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(Post Link) post #18 of 22 Old 15-10-13 Thread Starter
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They sure make it difficult for the average diy mechanic if it was not for the fact I have been working on my own vehicles for 30 yrs I would have serious thoughts about attempting any major work in these engines...rant over ;-)
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(Post Link) post #19 of 22 Old 15-10-13 Thread Starter
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Cry Like A Baby

Forgot to mention.....I have completely stripped the cylinder head and all 16 valves are bent and the 8 exhaust valve guides cracked where they protrude inside the head.
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Wow ... good job there ... I only bent about 10 valves and broke three guides when my belt went at 73k! And that was on the starter ... think it caught then stopped suddenly.

Still have the bits in a bag in the garage to remind me ... serves it's purpose, I get the belts done!

On mine the belt shed a patch of teeth and so when it got to the crank gearing it stopped turning ... and crunch!

Last edited by gazza82; 15-10-13 at 13:21.
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Sounds like it was a 'good' one. Hate to add to your woes, but you may well find the big ends have taken a hit as well.

Given what you already know about the damage, and what else may be lurking, that 63k motor from D&W sounds appealing....
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You have to know a key is just to locate the pulley and is not supposed to transfer any drive. The tension betwen the nut and pulley should be sufficient to transfer drive. If your pulley nut comes loose the key will shear.
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