So, you're saying the pulley spins freely on the shaft? So you can't lock the pulley against the pump with a bar to keep it from spinning?
If it's similar to my 98, it's not a spine, but a completely grooved insert. Don't think I've ever seen this.

 

 

Yes you can...
Insert a ratchet extension, or a large screwdriver, into one of the pulley holes to stop it from turning. Once it's locked in place remove the nut.

 

It might actually be more difficult to loosen that nut with the pump removed, since you'll need to hold the PS pump in a vise. While still installed, the car takes care of that for you.

What exactly makes you think something is loose? Does the pulley wobble? Does the pulley rotate as the shaft is held fixed?

If everything were working properly, with the engine stopped, you should be able to put a wrench on the pulley nut and turn it. Doing that would rotate the pulley nut, shaft, and pulley, with the pulley sliding past the belt.

With the belt removed, the pulley should spin freely, with very little resistance.

 

 

 

First take off the serpentine belt then remove that bolt then remove the pulley and look and see whats going on.

 

 

Woops I forgot its a nut, its been awhile fooling with one. It would be difficult removing the pump with the pulley still on and might not be possible because of bolt that needs to come out. You may have to try using a box end wrench and hitting it with a plastic hammer, an impact wrench would remove it but you won't get that in there unless maybe the radiator was out of the way. Last option is a cutting torch.

 

 

OK, still trying to figure out exactly what you've got going on there. The photo is helpful, and yes, that is definitely a problem.

So with everything still on the car, if you put a screwdriver through one of the openings in the pulley to stop the pulley from rotating, and then you try to remove the 17mm nut by turning it counterclockwise ... are you saying that if you do all that, the nut will stay on the shaft, the pulley will not rotate, and the shaft will rotate within the pulley? If so that would be really messed up since it is a splined interface in there.

Or something else?

Here is a PDF of the pump (from 2000), showing what that shaft is supposed to look like - splines on the back end, smooth in the middle, splines near the front to hold the pulley, and threads on the very front end for that nut.

 

 

 

Accurate written descriptions will definitely help.

Assuming you saw that PDF, do you have any reason to think that your pulley / shaft / nut etc. are a different design than shown there?

So if the pulley is rotating with respect to the shaft (vs. held firmly to the shaft by the splines), are you saying that you think it is because the splines in the pulley have slipped forward, off the ends of the splines in the shaft? If yes, that makes a lot more sense than somehow the splines being sheared off.

If that's the case, what I would do is to try to move things by hand to try to get the splines beginning to get lined up again (shaft vs. pulley splines), and then as carefully as you can, tap it back in. You're hopefully going to get the splines seated enough just enough that you can undo that nut. Not much needed there, unless there is a problem with the nut as well. But you need to be careful that you don't hammer it in there since the shaft is supported with a bearing and you will damage the bearing if hitting the pulley too hard.

If you can somehow get the nut off, then the pulley should come off as well, and you can hopefully clean up the splines and re-seat the pulley on the shaft carefully. If not, you're probably looking at getting a new pump.