What happens during cambelt failure? - Alfa Romeo Forum
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What happens during cambelt failure?

Hi all, just a question what happens when the cambelt fails on the car, is it possible to move the car in Neutral or does it seize up totally?


Alfa 156 2.0TS


Because i saw one for sale with a failed belt and wondering if i can use it for parts, but need to put in my garage after it gets towed.

Thanks in Advance
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The normal situation that occurs with a broken cambelt is that the cams stop turning but the valves are still being pushed up an down, hence bending the valves and possibly warping the cylinder head. If the car is a manual, you will have no problem pushing the car to wherever it is you require. I hope this helps. Good Luck!
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cool thanks, i just hope the crankshaft doesnt sieze which means the driveshafts wont move. Its an auto but if u turn the key to mar u can place it in neutral.
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These engines are known as 'interference' engines which means the top dead centre of the piston stroke, is higher than the bottom of valve stroke. - the pistons and valves interfere with each other so to speak, or overlap. Of course whilst the motor is correctly timed, the valves pull out of the way of the pistons just in time.

If the belt breaks, the cams do stop spinning, but the valves actually just stop going up and down. so the pistons smash into them.

Non interference engines don't have piston / valve overlap. So if a cam belt breaks on them, no big deal...

The problem with the TS and the JTS is that when you do have a cam belt breakage, the valves smash into the pistons with one hell of a bang, sending a shock wave through the motor and more often than not, screw the big ends up too. Not to mention a full top end rebuild - new valves, you'll have to recondition the head etc...

So make sure you have the bottom end checked too! I made the mistake of not checking big ends when my top end went.. and ended up having to replace the whole engine after a top end rebuild. If you don't the motor will lull you back in love with it for about 2000kms.. then the dreaded satanic knocking of spun out big end bearings will begin.. and there'll be tears for sure.

Last edited by Alfa156Melb; 29-09-12 at 07:35.
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Is it auto or selespeed? Either way so long as the trans is in neutral the wheels will turn and you can push it into your garage. If it has locked up the transmission for some reason you can still get it towed (front wheels off the ground) and then create a sort of dolly to support the front of the car while you manoeuvre it up your drive...think of a skateboard. Or Super cheap have wheel skates - they arent cheap but very handy...
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even if the transmission has locked in gear, simply take out the spark plugs so there is no compression at all, not that there will be much with mashed valves anyway.

HTH
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Ahh, I didn't properly read your question.. No the engine won't seize.. Purple is right, the valves will be part open even if you cant get it out of gear, the motor will spin - and with much less resistance than normal.
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(Post Link) post #8 of 8 Old 30-09-12 Thread Starter
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oh thanks guys, i was out yesterday, i am planning to use the other car as spares like, hoses, radiator etc, i wont touch the engine.
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