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Unfortunately, this is a very common complaint on the 2000 Mercury Cougar V-6 models and the issue comes from the overall way the vehicle was built. There is one TSB (Technical Service Bulletin) for your vehicle concerning brakes, but it does not affect the performance of your braking system. Details are below of the TSB.
By the way, I actually own a 2000 Cougar myself. I have owned it for a couple of years now. Mine does the same thing and I have inspected and replaced everything as necessary. The vibration is still there and upon researching the 2000 Cougar I realize it is just a flaw in this model. It will not hurt your braking performance any.
If you haven't done so already, you can get your front and rear end wheels aligned. This will help some of the vibration to fade but not all of it. It will also ensure your tire treads are making even contact with road which will increase the life span of the tires.
Hope this helps...
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Saturday, January 17th, 2009 AT 9:22 PM