I have a F150 p/u 2000 for 10yrs. Each year I change the brake pads. But the rear pads still looks like new. The front pads are worn down. What can be causing the problem?

You will need a special tool for the back brakes,Autozone will loan it to you for 60 bucks,you will get it back when you return,I used it.I replaced brake pads front and back and both back rotors.The driver side rear had metal on metal,all disc brakes,brake pads on that rear side were completely worn down to metal,the driver side was like new,kept wondering why,replaced both rear rotors,put back together,then then I noticed where brake line hose went into brake caliber was leaking,so that caused the side with new like brake pads not to be gripping disc putting all brake pressure of that one side,so the copper fitting their was bad,put new one on and leak stopped.

Pedal, not peddle. First make sure reservoir is full at the brake master cylinder. Then check your brake pads (for disc brakes) and/or brake shoes (for drum brakes). When the pads or shoes are very worn down, you will get a low pedal. If you have disc brakes on the front and drums on the rear wheels, first try just replacing the front brake pads. If you get a good pedal after the front is done, many people tend to let the rear brake shoes go unless they are making noise. These systems are designed to put most of the braking force on the front discs, so the rear shoes do not need changing as often.

Its possible. There is an equalizer valve that balances pressure to the 4 wheels.
Two other possible causes are a problem with the parking brake, or the front rotors and pads are glazed and not providing any friction.

Look through the openings in your front wheels and look at the front rotors-are they gouged up? You are probably running metal-to-metal, pads to rotors.
Chances are real good your rotors will have to be replaced along with new pads, but if you catch it early enough you might be able to have them machined, although nowadays that is hardly easy to get done and the savings usually is not as significant as it once was.

check rear rotors and front rotors for rust buildup (flahlight helps). does the vehicle shake when you come to a hard stop? You will either need to have a front or rear or both brake job (rotors cut or replaced and new brake pads) If the vehicle is shaking when coming to a stop, its probably your front pads. If your hearing the noise from the rear its the rear pads or it you hear it from the front its the front pads. If there significant rust build up or your pads are low a brake job is recommended.

check that your brake cylinder is not sticking after driving feel your wheel nuts if hot that could be your problem

Wiring them back together will fix the problem. make sur that you have pads with the wire

I'm going to assume you are talking about the front brakes since the brake pad warning light is wired to the front drivers side brake pad. Is this is the case you shouldn't put off changing the brake pads and rotors too long after the warning light comes on because you don't want to damage the caliper and cost yourself more money. Do them atleast within the next 500 miles if not earlier. The front brakes on the Jetta are standard single piston disc brakes. Buy decent new brake pads and you might as well buy new rotors instead of getting the old ones turned down (resurfaced, makes them thinner). You should also buy new brake fluid (good stuff) and flush the lines since VW recommends changing it every two years and it keeps the brake system clean and free of corrosion (saves money in the long term). Then you just jack up the vehicle, pop off the tire, loosen the caliper bolts, pull off the caliper making sure to still support it so the brake line doesn't get damaged (rig something up to hang it off the spring on the strut, i.e. bent metal clothes hanger), remove the one screw that holds on the rotor, pull off the old rotor, and remove old pads. There will be a pad sensor wire on the left front that you need to take off too. At this point you might need to push in the caliper piston in order to get the new pads seated correctly. There is no trick on the front calipers like the rear ones (the rear ones need you to turn the piston while pushing it in and is easiest to do with a special tool). You can use and old c-clamp or borrow a caliper tool fron a local auto parts store for the front. You should mount the new rotor first, then you might want to open the brake fluid reservoir (in the engine bay at the back, i.e. closest to cabin, in front of the driver), push the caliper piston back in, mount the new pads by usually sliding them on (use some brake quiet on the back if they don't have anything on them already), and put the caliper back on. The new pads might have the attachment for the sensor. You need to find out all the tightening values for all the bolts you remove and the best way for this is to buy the Bentley factory repair manual for your car (about $80). This will have the procedure I just outlined. It will also tell you how to change the brake fluid. The website forums.tdiclub.com will also have lots of answers for you and probably has pictures on how to do the work. I also recommend worldimpex.com or germanautoparts.com to buy whatever parts you need.

One thing I should mention, the rear brakes in these cars wear out long before the front brakes. If you have never had those serviced you should really look at them too. They may be down to metal on metal if the fronts are worn out.

My rear brakes were making the same sound for over one year. My rear shoes were hard as a stone or glazed. The pads did not look worn, but they made the medal-on-medal sound when I braked. It was pretty loud.

I replaced the brakes shoes and the problem went away. I replaced the shoes myself in about a hour. They were not hard to figure out.

Brakes can vary in the amount of time that they last. For starters there are many diffrent grades of pads, the cheap pads last me about a month, but the good expensive pads last me 6-8months or so, and I drive really hard. So depending on how drive can determine how long they last. Usually you can replace your rear pads once for every two or three sets of front pads you replace as most of the braking work is done from the front. Pads are made intentionally to squeak when they are running down, so when you hear that squeak get em replaced, but if the rear's aren't squeaking just change the front and do the rears next time.

Good Luck
Hope this help