Courtesy Lukenl8r !
A n00b how-to for a serpentine belt replacement on a Jeep 4.0 engine
Difficulty (out of 5)
Mostly engine grime. No grease or oil (hopefully)
1 15mm socket
1 6" socket extension (minimum)
1 Univeral Joint
1 new serp belt. Get it at your local auto parts store. I used a Goodyear Gatorback belt. They say its nice and quite, we shall see.
First, lets get orientated with the engine. My Grand Cherokee has the tried and true, 4.0 inline 6 that has been around forever. Below, you can see the grille of the Jeep at the bottom with the fan shroud in the middle, above the grille. To the left you can see the AC compressor and on the right you can see the power steering pump with the yellow cap and its pully wheel to its left. This is where most of the work will be done.
The first thing that must be done is to loosen the belt tensioning pulley. This is directly below the pulley for the steering pump. The belt runs over the back of it. Take your 15mm socket and loosen it until it wobbles. Do not take the bolt off as you will have a hell of a time getting it back on. Below, you can see the steering pulley in the foreground with the tensioner directly below it.
Next, you must find the adjustment bolt which is located behind and to the left of the steering pump. After the pulley is loose, you can take your 15mm again and unscrew this bolt until the belt its self is loose enough to get off. See the location of this bolt below. It is angled to the left towards the engine block and in a bad position. This is where your 6" extension comes into play. You can not get in there with out it. The 6"er was still tight so I threw on an additional 3" extension for the hell of it. If you dont have 9" you can get by with only 6.
After you find the bolt, loosen it up as far as you want. The looser it goes the easier the install is. After you get the pully to the point where the belt will slip off, wiggle it around until you can get the belt off of the rest of the wheels. Pay attention to the direction of the belt with respect to its pullies. If you dont know the direction, here is the diagram of the routing which should be on your fan shroud.
Now that the old, cracked belt is laying on the ground, you have to put the new one on. The easiest way to do this is to have a second set of hands. If not, you can still get it on, but it will be a bit tougher. Crawl under the Jeep and start from the bottom and work up. Start on the fan clutch then work around until each pully has the belt around it. Any wheel that is grooved must be on the inside of the belt to accept its grooves and the smooth pullies go on the outside. The last pully to go is back on teh belt tensioner. It is likely that you will need to loosen it a bit more as the old belt would have stretched a bit. The new belt is tighter so you will need to open the tensioner a bit more. After the belt is on screw the adjustment bolt back down until the belt can twist approximately a quarter turn or less. While tightening the adujustment bolt down, you should also tighten the pully its self in increments so it is not out of allignment. After the tensioner is nice and tight, screw the pully's bolt back down as well.
Here is the old belt. You can clearly see the cracks in the grooves. Time to replace it!
Thats it. 25 minutes later the new belt is on. This will probably take closer to 15 with help.
Disclaimer: I am not responsible if you break anything on your vehicle attempting a repair. If you screw it up, thats your own fault. This is for information purposes only