Question: I just had serpentine belt changed

I have a 2000 Grand Prix GT and it has run effortlessly for as long as I've had it (0 - 100k miles). 1 week ago, I got the serpentine belt replaced and immediately after picking up my car, I noticed when pushing the gas or going up low grade hill or more, there was slightly more throttle/deeper sound under the hood and at 55mph or higher, it takes more effort to go.

I took the car back and the lead mechanic said the belt was on correctly and sent me on my way. My neighbor said that it could be the spring pully.

Any ideas why this immediate difference was noticed following the serpentine belt change? I've never, in the life of the car, ever had to so much as lightly touch the gas to fly effortlessly to 70 - 80 mph. It's nothing horrible and the car idles beautifully, it's just a change that I don't like. I travel alot and I've always loved the smooth, quiet, effortless ride on the expressway. Any thoughts?

Thanks.
nikkib

Answer: While it seems like a strange "coincidence" that you should notice such a change immediately after having the serp. belt replaced, I believe it's only a coincidence.

The serpentine belt drives the accessories on the car such as the water pump, alternator, power steering and A/C. Technically, the vehicle will run without this belt (although it may overheat because the water pump isn't turning and your A/C and power steering wouldn't work and your battery will eventually drain because the alternator isn't charging it). What I mean is that the serpentine belt has basically nothing to do with the running or performance of the vehicle.

I applaud you for taking the car right back and having it re-checked. I wonder if maybe you were sent on your way because the shop is more of a maintenance shop rather than one who would have the tools or equipment to diagnose such a performance problem. Sounds like you need to find a shop in your area that performs "driveability diagnosis" or "analysis" to find the root of the problem.

Good luck!