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james999's Avatar
 
Join Date: Jan 2007
Location: South Africa
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Timing belt shredded

Could anyone please help?

My 78 924 was running fine on the high way on the way home, i then parked it for the night and when i started it the next morning the rev's just would not go up and the engine wanted to die.

some problem shooting later found my timing/cam belt was missing all it's teeth and was torn in the middle on the one section. It was a brand new belt less than 2000km ago. did I mess up with the installation or did a stone maybe go through the system and make it jump a tooth and then that cause the rest to wear down?

is it possible to mess up the cam belt installation in such a way as to cause that amount of damage?

Old 05-20-2008, 05:15 AM
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I dont have knowledge of a 924 but I doubt it. There must be a mecahnical fault that caused a cam or roller to damage the belt. My uneducated guess is that if a belt is too loose, or if it looses tension that a cam might be able to jump a tooth on the belt, or half a tooth, and start damaging the belt, a tooth or two on the belt can be ripped off and accelerate the further destruction of the belt. Difficulty in starting / engine wanting to die could be an idication of the timing that is out - possible evidence of a damaged belt, slipped a teeth or two. I am under correction but I think the 924's are not interference engines - so no valve damage.
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Old 05-20-2008, 11:34 AM
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The 924 is a non-inteferrence engine so no harm. Check the teeth on the pulleys for rough spots. Try a new belt. Make sure you tension it right, all you need is the 90 deg twist test.
Make sure the belt stays centered on all the pulleys. Haynes covers it pretty well.
Such a simple engine......

Good luck,
Jon
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Old 05-20-2008, 05:52 PM
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I set it up centred on the pulleys, last i checked it was centred on the pulleys and even with all the teeth ripped off it was still centred on the pulleys. i did the twist test and all when setting it up originally. but i will try again with a new belt.

Would anyone know how many teeth the standard belt has? and thanks for the help so far, much appreciated....
Old 05-20-2008, 08:54 PM
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Ok, so I went to the parts place and got a new belt, standard size. But the one guy behind the counter who owns and fixes VW's says that the rule of thumb 90 degree twist turn doesn't exactly hold for VW's, and they actually need to run a bit looser. Cause when he looked at my old belt he immediately said it's from over tensioning. so new belt in, car running fine and now to wait and see if it happens again.
Old 05-21-2008, 08:42 PM
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Another possibility is if the timing belt is driving the water pump and the water pump is seized then there will be a lot of stress on the belt and the belt will fail early. If it fails again try checking that all the moving parts in the belt area are moving freely and keep an eye on the belt every day to see if it deteriorates prematurely.
Old 05-21-2008, 11:54 PM
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the water pump is run off the V belt and should not affect the timing belt? but on a similar topic, how easy must it be to rotate the belt tensioner? I installed a new one with the first belt i put in, but it still offers some rotation resistance. should it rotate easily, like if you spin it it will keep spinning a bit? Mine doesn't...
Old 05-22-2008, 12:03 AM
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no. if it keeps spinning, the bearing is worn out.

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Old 05-22-2008, 07:44 AM
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