When should I install a new serpentine belt on my 2000 Mercury, Grand Marquiz

when its worn, have your mechanic check it out

You should probably do it in the daytime when it is light.

look for glazing on flat side and cracking on ribbed side

If it looks warn, l would replace it. If there is not glazing or cracking and nothing squeals, l would wait until you have 35-45,000 miles on the car. If that belt breaks, you will be out of business. They never break in your driveway of while you are getting your oil changed. Make sure you check your belt tensioner at the same time. Those go bad and will ruin a good belt quickly.

When the belt starts to get alot of cracks in it or when it starts squealing.

On the average, they should last 60,000 miles. But the best time to change it is right before it breaks. The belt is not cheap, but it is about a 10 minute job, so if you have any doubts, or it looks the least worn, do it and then you wo not have to worry about it.

Wow, the car is almost new. You do not have the service manual anymore? If not, you can go online and download a .pdf file from Ford.

Good question. My 88 Ford F-150 with the 5.0 in it had 215,000 miles on it when l sold it. l never once replaced the serpentine belt, never had reason to.

When the inside looks cracked, or the belt seems worn.
Belt last a very long time on that car.

When it looks very badly cracked on the pulley side, and when it is about 10 years old. Normally, these last 100,000 miles.

A rule of thumb, if it has more than 10 cracks per inch, it needs replacing

no, get a mercury villager mercury.com

soon

before the old one breaks