Technical Fiat Stilo 192 A4000 1.8 16V Bottom Cambelt Pulley

[burtontrent]

I bought a 1.8 16V Fiat Stilo,have noticed that due to the vehicle breaking a cambelt, at 160,000kms probably it had never been changed?
So, I noticed that when it broke, somehow, it has sheared the 'woodruff key' which is a cast part of the pulley. When renewing parts to do this job, it will be necessary
to check the condition of the pulley. Otherwise of course the timing will be subjected to going out and probably cause even more valves to bend.
I had to change 8 exhaust valves, all of the inlets were not touched in the mishap.
Also just doing a 'Citroen C4' which has only bent 4 valves with a broken cambelt so will be less an expensive fix.

 

[Maxcaddy]

Can't quite image the failure mechanism which caused the crankshaft gear to shear its key , unless the nut/bolt was loose. The 1.8 I had was changed twice, but I'm fairly sure that the gear didn't have to come off or be loosened. When the belts go they usually loose a few teeth at the bottom which lets the crank spin while the cams have stopped. Hence not sure what would have caused the steel gearwheel to come off worse than bits of belt.

However if the damage is contained to a set of valves and a gasket set, with a bit of work you've got yourself a winner .

 

[burtontrent]

Can't quite image the failure mechanism which caused the crankshaft gear to shear its key , unless the nut/bolt was loose. The 1.8 I had was changed twice, but I'm fairly sure that the gear didn't have to come off or be loosened. When the belts go they usually loose a few teeth at the bottom which lets the crank spin while the cams have stopped. Hence not sure what would have caused the steel gearwheel to come off worse than bits of belt.

However if the damage is contained to a set of valves and a gasket set, with a bit of work you've got yourself a winner .

I had exactly the same thought of how would the Crank Pulley woodruff which is part of the gear casted, How would it shear off? Only thing I could come up with, somehow the belt got caught when it broke and was cut all through by the way, locked up the engine somehow caused an instant lock up? Mmmm, Bit doubtful though? The bolt inself was really tight. But thanks Max.

 

[Maxcaddy]

Sorry, I must pay more attention , you did in fact say "sheared the 'woodruff key' which is a cast part of the pulley", which I simply read as sheared the woodruff key (full stop).

To be fair it's been quite a few years since I last did a 1.8 belt, and at least 3 since I did my 2.4 one which I think had virtually the same arrangement, so does the "cast part of the pulley" refer to the crankshaft drive gear itself, or the pulley that fits to it to drive the auxiliary drive belt ?. If it is the pulley and it's a big lump of metal, then its secondary function is be a crankshaft balancer and as such is done up seriously tight.

 

[burtontrent]

Sorry, I must pay more attention , you did in fact say "sheared the 'woodruff key' which is a cast part of the pulley", which I simply read as sheared the woodruff key (full stop).

To be fair it's been quite a few years since I last did a 1.8 belt, and at least 3 since I did my 2.4 one which I think had virtually the same arrangement, so does the "cast part of the pulley" refer to the crankshaft drive gear itself, or the pulley that fits to it to drive the auxiliary drive belt ?. If it is the pulley and it's a big lump of metal, then its secondary function is be a crankshaft balancer and as such is done up seriously tight.

Hi Max, yes the pulley that fits first on the crankshaft that the Cambelt runs on has a cast woodruff key that is actually part of the pulley, so if it strips the woodruff, a new pulley is the only way to repair it. The whole cambelt pulley must be machined out of one piece of steel, How it is done I do not know , but it is very cleverly done. The crankshaft bolt was very tight, is a L/H Thread. The serpentine pulley bolts to this one afterwards,when the cover has been fitted.

 

[124BC1]

--------------------------------------------------------------------------------------------------- so if it strips the woodruff, a new pulley is the only way to repair it. --------------------------------------------------------

Might it be possible to cut a keyway/groove inside the timing belt pulley (sprocket?) and use a suitably sized machine key?
Here's a link to a U.S. website showing a wide variety of machine keys available - you could probably find something suitable local to you from an Engineering Supply company or simply make one yourself.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

From what I can gather, some quite complex modern engine parts are made from 'sintered metal' (sintering) rather than using traditional casting or machining techniques. To see examples of this process and an explanation you could try an i/net search using words such as "sintered metal components"

 

[burtontrent]

Might it be possible to cut a keyway/groove inside the timing belt pulley (sprocket?) and use a suitably sized machine key?
Here's a link to a U.S. website showing a wide variety of machine keys available - you could probably find something suitable local to you from an Engineering Supply company or simply make one yourself.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

From what I can gather, some quite complex modern engine parts are made from 'sintered metal' (sintering) rather than using traditional casting or machining techniques. To see examples of this process and an explanation you could try an i/net search using words such as "sintered metal components"

Hey thanks for that heads up! But, I rang the 'Italian Auto Centre' In Auckland,NZ. He sent me a second hand good one that they had for NZ$85.00
So I was pleased with the result it is already fitted and ready to go. Thank you for your information quite amazing what clever engineering they can do today. Burton Trent