Serpentine Belt 4.0 Jeep

[Kandy Swartzel]

Pleasenote: This writeup was completed on my 2001 Jeep TJ with a 4.0L I-6 engine, and it also worked on my 1998 Monte Carlo Z34 with a 3.8L V6 (it should also apply to Cherokees, Grand Cherokees and Wranglers with the 4.0L). Although engine layout/design will vary amongst auto-manufacturers, the basic ideas and principles in this writeup should apply to many vehicles with a serpentine belt system.

Every 30,000 miles I replace the serpentine belt in my vehicles whether they look like they need it or not. A serpentine belt is an inexpensive way to make sure that you won't get stranded from a broken, rotten, old serpentine belt. With age, your rubber serpentine belt will begin to crack and dry-rot, and could possibly break at the worst possible place. This belt is also known as the "accessory belt" or "fan belt" and it is a way to transfer power from the rotating crankshaft to drive necessities/accessories such as:

On most vehicles that are driven regularly, belt replacement every 30,000 miles is almost TOO frequent. To find out how to check and see if your belt is needing replaced or not, check my belt inspection writeup. When I replace my belt, assuming the old one isn't totally trashed, I put the old one in my trail box just in case a buddy (or heaven forbid ME) needs a spare belt.

First, open the hood, get out the shop light and 3/8"-drive breaker-bar/socket-wrench. I suggest using a breaker-bar if you own one; I completely destroyed [read: exploded] a socket wrench doing this one time...the pressure required sometimes is more than what a socket wrench is designed to withstand. Now, locate your "Belt Routing" diagram, which is a decal that should be affixed to the top of the radiator or on the sheet metal under the hood somewhere quite visible.

After finding the routing decal, locate belt tensioner. In the picture below, the red arrow is pointing to the belt tensioner's 3/8" square hole for your breaker bar. That silver, oval-shaped metal arm is the tensioner.

Now, insert your wrench/bar in the hole pictured in step two. As you are standing at the front of your Jeep facing to the rear, you want to use your wrench/bar to rotate the belt-tensioner arm clockwise (depicted by blue arrow below); this will be towards the ground in most cases. This removes the tension from the belt. While the tension is removed from the belt, pull the belt towards the front of the vehicle (shown by green arrow below) and slip it off of the tensioner. If you have difficulty slipping the belt off of the tensioner, try to slide it off of one of the many other pulleys instead.

Now you can release pressure on the tensioner. This step involves completely removing old belt. For my TJ, it involved getting under the Jeep to detangle everything off of the BIG crankshaft pulley and to route then belt around the fan blades.

Now that the old belt is off, get out the new belt and put it back on in the reverse way that you took it off, pretty simple! Once you have it put back together, clean up your tools and start your Jeep and listen for any new strange sounds (like a belt slipping or rubbing). Note that a Gatorback belt makes a zippy, whirring sound; don't confuse this with a REAL problem. Close the hood, you're now done.

I have a problem with the belt on my '89 six-cylinder Jeep Cherokee. It was fine, but then the serpentine belt began to shred. I replaced it, and the new one began to shred, too. I noticed that the belt was shifting off of the pulley that is located on the crankshaft. It wasn't moving much, but it had moved exactly one groove closer to the engine. I tried another new belt and tightened it more. But halfway through a test drive, it was shredding, too. Can you give me any advice?

RAY So, now most cars have a serpentine belt, which is a long belt that runs all over the engine and runs everything. The real advantage of a serpentine belt is that it's easier to change. You don't have to reach your fat arms into little skinny openings to change multiple belts. You change one belt, and it's done.

TOM This belt runs over and around many pulleys that power the accessories, and it sounds to me like one of those pulleys is out of alignment. That's what's pulling the belt off-line and causing it to shred.

RAY If you've had one of the accessories replaced recently -- like the alternator or water pump -- I'd suspect that that pulley is now lined up incorrectly. It could have been manufactured incorrectly, or it could have been the wrong pulley for your engine. A pulley only has to be a few millimeters off to set a belt a-shreddin'.

TOM Another possibility is a bad idler pulley or tensioner pulley. Those are sort of "dummy" pulleys that are used to alter the direction of the belt. If a bearing goes bad on one of those pulleys, it tends to tilt, and that could cause the belt to shred.

RAY The worst possibility (for you -- if your mechanic has kids with tuition payments due, this will be good news for him) is the crankshaft pulley itself. It could be the harmonic balancer portion of the crankshaft pulley, or -- the worst-case scenario -- too much end play in your crankshaft.

RAY But unless you can clearly see that one of the pulleys is not in the same plane as the others, it's going to be hard for you to figure this out yourself. So I'd recommend taking it to a mechanic. I know it'll cost you a few bucks, but think of the fortune you'll be saving on belts, Ricky.DEAR TOM AND RAY

I own a '99 Pontiac Grand Prix with traction control, which makes sense to have in the Midwest, my fair region. There is a button on the dash that allows me to turn it off, should I desire to do so. I travel and rent cars frequently, and I've noticed that other makes that have traction control have an on/off button as well. Why, in the name of Britney Spears' bare midriff, is this the case? Under what circumstances would the average driver turn it off, and would he or she know when the proper circumstances arise? I certainly don't!-- Larry

TOM Good question, Larry. High-school kids were finding it impossible to "do doughnuts" in the school parking lot with their dad's traction-control-equipped cars, so the automakers thoughtfully added an on/off switch.

RAY Actually, the off switch is for situations where the traction control works too well. Traction control prevents the wheels from spinning when you accelerate. This prevents the driven wheels from breaking away and skidding.

TOM But there are a few rare circumstances in which you might want the wheels to spin. One is if you're stuck in the snow. If you're stuck in the snow with the traction control on, here's what happens The wheels will try to turn, they'll get no traction and they'll stop. So, in a situation like that, the traction control can prevent the wheels from turning at all. No traction, no power to the wheels!

RAY So by turning off the traction control, you can allow the wheels to spin, and you can try to get out of the snow the old-fashioned way -- by rocking the car back and forth ... and digging a 2-foot hole under each wheel that you'll never get out of.

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