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A friend of mine owns a 155 Q4 with the 2.0lt turbocharged 16v engine. His cambelt broke for the second time with less than 20000 km (12500 miles). He's a mechanic, and keeps everything in shape. What can be happening??? He suspects there's a problem with the crankshaft belt gear (gear teeth too short or worn out).

Anyone have a clue? The belt was Dyco.

Thanks,

Diego
 

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is he over-revving the engine ? letting the cutoff coming in ?
I've heard that sometimes that makes the belt jump a few teeth and then breaking off, it is the jolt that causes this.
 
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Hey rarebear, thanks for the response.

Well, to tell the truth, the first time he drove me in his car, he hit the cutoff so I could see how fast his car accelerated. Quite a drive!!! :D

I don't think he does it too often though. The belt cut a near idle speed.

Aren't the belts designed to hold, even if you hit the cutoff? The engine is designed to run at 6000 rpms, and go from 0-60 in roughly 7 sec.
What the sense of owning an Alfa if you can't step on it?

Ofcourse I've never hit the cutoff on my car, hell it hasn't even been to 6000 rpms.
 

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well to tell the truth, some years ago I really hit the metal and ran the revs till the cutoff in 4 gears, no problem. Next day I was driving in a traffic jam about 30 km/hr and all of a sudden the engine died on me. I started , but only a turbine like sound and no engine start.
The belt tensioner had exploded, ruined the complete valve train and pistons. It so happened that the car only had 8000 km and was within warranty and the tensioner was a bad part (Candadian made) and more cars suffered the same problem (Opel) but since then I am very careful to not reach the cutoff revs ... (rev counter is a good tool in an Alfa)
I quess the 155Q being a turbo car, did not ruin the valves ?
 
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Man, I hate to read the rev counter (even though I really do). These are sports cars we're driving, and they should work fine, but on the other hand they have high output engines and their parts are more stressed than in normal cars.

I would assume that the belt and tensioners are designed to work at higher loads than what the engine gives, but the cut off is there to protect the engine from damage. I guess that means that you can't hit it everyday with no problem.

16 valve engines put higher stress on the tensioners, I've heard of 16v 33 having problems too with the canadian made parts.

The Q4 ripped the belt's teeth clean, it didn't snap. I saw the engine disassembled yesterday, the pistons luckily were OK, just a small insignificant mark on them. The valves, well eight died.
I hope this never happens to my engine. The parts alone would probably add to half of what I paid for the car.
 

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Ok Man, count your blessings, only 8 valves and pistons OK, I had 16 valves bent and 4 pistons dented.... lucky that I had a valid waranty ! would have costed 2000 usd to repair.
btw what turbo does the car have ? a Garrett ? or KKK ?
 
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If I'm not mistaken, the turbo is Garret. It's set to boost pressure up to 850 gr/cm2 (12 psi).
The car really starts pulling at 2300 rpm (max torque).

Diego
 
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