What size bolt is it for the idler pulley for 1997 jeep grand cherokee larado?

if there is nothing wrong with the ac pulley bearing , just disconnect the power to the compressor and use it as an idle pulley
because the ac pulley is in the system , and another belt that by passes that pulley will have the belt grooves running on a flat idler and the belt life is considerably reduced to over come that will require another idler pulley and bracket

i posted this yesterday
1-1/4" or 32mm
buy and use a caliper to measure bolts.

1998 Jeep Grand Cherokee 5.2 Liter And 5.9 Liter Serpentine Belt Routing try this link http://autorepair.about.com/library/pictures/illustrations/bl750a-lib.htm

Your threads should be standard right hand. Don't worry about the pulley turning when you break the bolt loose. The bolt is isolated from the pulley by a bearing (the one that failed) so the two turn independent of one another.

Good luck.

The indented middle part or concaved side goes on facing front of vehicle.

right, for the 4 liter,

1. Loosen the rear power steering pump mounting bolts using a ratchet and 13mm socket or a 13mm box wrench.
   
2. Loosen the pump upper pivot bolt, lower locknut and the pump adjusting bolt using a ratchet and 13mm socket or a 13mm box wrench.

For the V8

1. Attach a socket or wrench to the pulley mounting bolt on the automatic tensioner and rotate the tensioner assembly clockwise until the tension has been removed from the belt.
   
2. Remove the belt from the idler pulley first and then from the vehicle.

Should only be one bolt going thru the center of the pulley. probably a 14 or 15mm size.

most likely a worn idler pulley or a part that has a bad bearing or going bad.

If you have the same pulley arrangement that most 4.0 engines have that pulley is an idler not a tensioner. Your power steering pump has a pivot bolt, and a slide under the pump. You adjust belt tension using the pump.

1994 is the same as 1997. parts are interchangeable