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Hi guys,

Question:

Since a couple of weeks, I have this interesting phenomenon on my 308GT4 engine:

When it is really cold (about 2 minutes after starting), it will produce a very distinct rattling sound, coming from the righthand side of the engine (cambelt side). It will rattle for about 15 seconds, and then the noise is gone again, not to return until the next cold start.

The rattling continues when I stop the car, so it is not wheel or transmission related.

Coming from the cambelt side, I am thinking of idler pulleys.

Makes sense?

Any other ideas?

Thanks!

Hans :(
 

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Hans,

i bet it sounds like ball bearing caught in a blender. The faster you rev the engine the faster the 'ball bearing' sound goes. What you have is normal, it is the air conditioning belt system. As you noted, the sound goes away in a few moments as the engine expands and everything gets warm and happy. There is really no full solution other than removing the air conditioning system.

i tried solving the same thing on my car and realized there is really nothing wrong and just ignore the sound... but then due to racing the car i removed the AC system so no more worries :)

Relax, everything is probably fine with your car.
 

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Hans, if Steven is correct, there is an easy way to confirm the diagnosis. Remove the A/C belt and see if the noise goes away :) -Steve
 

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Just spray some belt conditioner on the ac belt and see if the sound goes away. If it does, cut it off really clean the wheel and replace the belt....

mike
 

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Mike, that will tell you if you have a bad belt, but won't help diagnose a bad bearing in the compressor clutch. Removing the belt does both. -Steve
 

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I agree with Steve and Steven, it is probably your A/C clutch. Take the belt off and leave it off. You could spend a bunch of money fixing it, but do you really use the A/C that much in the Netherlands?
 

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Well that definately eliminates the A/C as the suspect. :)
A bad alternator bearing would be more of a whine or howl. I've never really heard water pumps make any real noise but that could be the problem. It could also very well be the idler pulley as you originally suspected. You would want to get that checked out soon. If an idler pulley fails the results can be catastrophic.
 

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Right next to the crankshaft gear are two shafts that support the lower belt gears. Each has two bearings, the outer one being a sealed ball bearing, and they are known to fail. One thing you could try is to remove the inner fender and the two belt guards, and use a stethoscope to try and pinpoint the noise. Idler bearings are easy to replace, but those lower bearings are not. I agree that it would be wise to find the problem before you have a disaster. -Steve
 

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Try putting some belt dressing on the water pump belt. It can be any accessory belt.

Mike

note. mine sounded just as you describe, sprayed the belts, no more scary sounds.
 
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