Hello I have a 1997 Bonneville and the tensioner pulley seems to be bad. On the black pulley the belt is all the way to the edge of the puller. I was told by a mechanic I need to replace the whole assembly. Napa told me they have just the pulley. It is likely to be just the pulley? If is the whole tensioner how do I replace it. I am just starting to learn to work on cars so any help or advice you have would be helpful for me or pictures or what. i have never changed a belt either.

Is it possible to get a picture of what your talking about? If the pulley is bad then ya, you can change just the pulley. There are some write ups in the tech info area about changing belts, etc.

Take the belt off if there is play in the pulley can just change the pulley if the whole assembly rocks then probably the whole assembly. But be careful driving dont need the belt falling off and wrapping up plus all the other things that can go wrong. check too to see if the belt is centered on the rest of the pulley not showing any ribs. check the tensioner and check back in

Here is the pic that was requested.

mine looks close to that (I think is ok ha) check the play when you take the belt off

Well, it'* not down the center of the pulley but it'* not hanging over the edge either. As long as the tensioner spring is firm that should be OK. I don't believe that belt will come off. The grooved pulleys hold the belt in place

whats the pully under that I forget power stearing? check play in that might be pulling it out

The mechanic I took it to seemed fairly certain that is why it squeals badly. He told me you cannot change the pulley but I heard I can. He just looked at it with the hood up he didn't use any tools. But to make sure I understand if I loosen that bolt on the pulley pictured I can slide the belt off?

Belt screaming could mean you need a new belt. But it does look ok from the pic. Hard to tell.
Does look like the belt is near the edge of the tensioner.
Whats very easy to do. To check. Find a socket that fits over the nut of the tensioner pulley.
Do you have a long socket wrench ? If not use a hollow bar over the wrench handle.

Im surprised your mechanic didnt show you this. It only takes a sec....

Apply pressure so as to move the pulley away from the belt. You can then remove the belt from that pulley.
Be careful so as to place the belt in position to remember how it came off. Dont remove the whole belt from everything. Gently remove it from the one whilst watching and recalling its original path around the others.

Now you can check the bearings on all the pulleys. Spin the tensioner pulley. Feel it, wiggle it to see if it has any play. If it has up down, left right play, then the bearing is shot. You buy a new pulley.
The chances that you need a whole new spring system are kinda between slim and nil, And slim is outta town LOL.

You dont even really have to remove the belt from anything. Just use the socket wrench to release the tension. And you can feel the pulleys that way.

As long as your not leaking coolant then chances are your coolant pump/pulley is fine. If it squeals while turning then it may be your power steering pump.

Be aware though. If it is your tensioner and when or if you replace it. There is a chance that your coolant pump may begin to leak. The extra pressure could cause that.

Why would there be extra preasure when replacing the tensioner?