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Old 12-03-2013, 07:14 PM   #1
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Default How to replace 4.2 Serpentine Belt, Tensioner, and both idler pullies

After getting gas yesterday am on start up suddenly there was a rather loud whine that increased with engine speed. Drove the 700 miles home and today got the parts for replacing the engine belt and respective pullies. While fresh in my mind, hope this description helps someone.
Vehicle: 2000 F150 XLT with 4.2 V6 and a/c and 65,000 miles
Tools needed: flat blade screw driver, T50 Torx Drive socket (a good quality one), breaker bar, 15 mm socket, ratchet, sandpaper, small hammer
New parts needed: serpentine belt, belt tensioner with pulley, smooth idler pulley (upper), grooved idler pulley (lower)
Time: about 30 min to 1 hour

Not knowing which pulley was noisy I decided to replace the belt and both idler pullies.

Belt removal
Remove the air intake tube from the throttle body using the screw driver. Unhook the clamp from the air cleaner. Move the air intake out of the way.
From above, using the breaker bar and 15 mm socket on the belt tensioner bolt, rotate the breaker bar to the left counterclockwise. The label with the belt schematic mentions this. With the belt tension loose, slide the belt off and remove.
Slip the old belt over the 11 fan blades one at a time until the belt is free or cut off the belt.

Spin each pulley and listen. You will hear the bad bearing. Don't forget to spin the alternator and listen, just in case. My lower idler pulley was bad.

Lower (grooved) idler pulley removal
From below, using the T50 socket, loosen the grooved idler pulley. You want to pull down to rotate counterclockwise. It will be tight so you need a good quality T50 socket. Otherwise it will break.
Remove the pulley and bolt. The bolt gets tapped out and reused.

Belt tensioner removal
From below, using the T50 socket, loosen the bolt for the tensioner. Pull down to rotate counterclockwise. Notice that the pulley is on the left. Remove the tensioner. Using sandpaper, remove the corrosion buildup where the tensioner was mounted. You want a flat surface for the new tensioner so the pulley it aligned properly. The bolt gets tapped out and reused. Don't worry about the o-ring on the bolt. It was only there for the assembly line people.

Install the new tensioner and pulley. Install the new lower idler pulley.

Upper (smooth) idler pulley removal
From above, using the T50 socket, loosen the bolt for the upper idler pulley and remove. The bolt gets tapped out and reused.
Install the new upper pulley.

Belt installation
Slip the belt over the 11 fan blades one at a time until it is on the engine side of the fan. Straighten the belt so the grooves are on the inside. Look at the label to see how the belt gets routed. Start by slipping the belt under and around the engine pulley, then around the fan pulley exactly as shown on the label. Wrap the right side around the a/c compressor and power steering. Then go to the left side routing from bottom to top. Leave the routing for the upper idler pulley for last.
Now the fun begins: using the breaker bar and the 15 mm socket, rotate the belt tensioner to the left (counterclockwise). Begin with the breaker bar resting on the fan pulley to get max movement then move left.
While holding the tensioner full left, slip the belt over the smooth upper idler pulley. It is easiest to slip the belt over the smooth pulley last. Inspect the belt to be sure it is routed correctly and properly in the grooves.
Reinstall the air intake. Don't forget to tighten the screw.

Hope this helps someone.
TomB275 is offline   Reply With Quote
Old 12-03-2013, 07:14 PM

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