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5-8 minutes sounds a little extreme and not very environmentally friendly.
Is warming this long actually bad?

 
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just a waste of gas at that point.

 
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5-8 minutes is probably okay. It's when you start it, run back inside and for get and 20-30 minutes later you remember. Running that long in place can cause flexing to the heads. Not much though, so don't worry if you do it once or twice, but if you make a habit out of it, you may end up with some bent heads.

 
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i've waited 5 minutes before, but that's only so that the windows and i defrost before goin on the road.

 
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Lately it's been quite cold and when warming up I can wierd noises from under the hood. Sounds like belt noise. Kind of like "ch ch ch ch". Can't describe it. But after I've driven the noise is gone. Could the belts be going bad? What does a bad water pump sound like?

 
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I would have to say it SOUNDS like belts. But figuring a sound out over the internet is hard, you're best to take it to a mechanic to have it looked at.