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The Aerostars in the 80's had two belts. One required a breaker bar to adjust, and lock in place while the other had a bolt which tighted to achieve the desired amount of tension. The 4.0L Aerostars in the 90's started to use an automatic belt tensioner with only one belt. The 3.0L started to use an automatic belt tensioner with one belt in the mid 90's.
The advantages of having an automatic belt tensioner:
1. The belt will last longer since it can't be over tightened.
2. It makes it possible to replace the belt without tools if you pull on the belt to adjust the tensioner. Some people might have trouble doing this, but I've done it several times so I know that it's possible.
3. It's easier & cheaper to replace one belt than several belts.
4. There are less brackets & bolts with adjustments, so the parts count is lower.
Here is a picture of the kit that is used on the 3.0L engine:
It was purchased in Autozone, and came complete with the pulley, and installation hardware. I replaced both idler pulleys at the same time, but had a problem with the ones that they gave me. The OEM pulleys were metal with a smooth surface. The replacements were slightly smaller, plastic, and had raised sides. As a result, I had to use a larger pulley on the idler to compensate for the smaller diameter of the two idler pulleys because the belt was too loose. Here is a side by side comparison:
As you could see, the older one in the photo has a larger pulley that is used on the 4.0L engine. This is the installation kit:
This is a comparison of the new hex head bolt, and the OEM T-50 Torx bolt:
The hex head bolt was slightly longer, but fit well since the head was low profile. The Torx head bolt had a much higher head, so clearance was an issue when the larger 4.0L idler pulley was used on the tensioner instead of the pulley that came with it.
The replacement of the part was not complicated after resolving the pulley diameter issue. Here is a photo of the old automatic tensioner being removed:
The T-50 bolt wasn't tight, so an ordinary 3/8" ratchet was used to remove the bolt. Installation of the tensioner requires an alignment pin in the back of the tensioner to go into a groove in the engine. Here's a rear view of the tensioner:
This is the front view of the tensioner with the pulley that came with it:
The larger pulley from the 4.0L was a fraction of an inch away from the center hole where the bolt goes through.
After you install the tensioner, follow the belt routing diagram under the hood, and check each pulley for proper belt alignment.
The advantages of having an automatic belt tensioner:
1. The belt will last longer since it can't be over tightened.
2. It makes it possible to replace the belt without tools if you pull on the belt to adjust the tensioner. Some people might have trouble doing this, but I've done it several times so I know that it's possible.
3. It's easier & cheaper to replace one belt than several belts.
4. There are less brackets & bolts with adjustments, so the parts count is lower.
Here is a picture of the kit that is used on the 3.0L engine:
It was purchased in Autozone, and came complete with the pulley, and installation hardware. I replaced both idler pulleys at the same time, but had a problem with the ones that they gave me. The OEM pulleys were metal with a smooth surface. The replacements were slightly smaller, plastic, and had raised sides. As a result, I had to use a larger pulley on the idler to compensate for the smaller diameter of the two idler pulleys because the belt was too loose. Here is a side by side comparison:
As you could see, the older one in the photo has a larger pulley that is used on the 4.0L engine. This is the installation kit:
This is a comparison of the new hex head bolt, and the OEM T-50 Torx bolt:
The hex head bolt was slightly longer, but fit well since the head was low profile. The Torx head bolt had a much higher head, so clearance was an issue when the larger 4.0L idler pulley was used on the tensioner instead of the pulley that came with it.
The replacement of the part was not complicated after resolving the pulley diameter issue. Here is a photo of the old automatic tensioner being removed:
The T-50 bolt wasn't tight, so an ordinary 3/8" ratchet was used to remove the bolt. Installation of the tensioner requires an alignment pin in the back of the tensioner to go into a groove in the engine. Here's a rear view of the tensioner:
This is the front view of the tensioner with the pulley that came with it:
The larger pulley from the 4.0L was a fraction of an inch away from the center hole where the bolt goes through.
After you install the tensioner, follow the belt routing diagram under the hood, and check each pulley for proper belt alignment.