How do I loosen the tension pulley on the serpentine belt to remove the alternator?

Rotate the tensioner using a 3/8 in socket driver to loosen the belt. Carefully remove the belt form any pulley. Release the tensioner and replace the belt on all pulleys except the alternator. Rotate the tensioner again and put the belt over the alternator pulley. Release the tensioner and verify the belt is properly engaging all pulleys.

ADJUSTMENT

Excessive belt tension will cause damage to the alternator and water pump pulley bearings, while, on the other hand, loose belt tension will produce slip and premature wear on the belt. Therefore, be sure to adjust the belt tension to the proper level.
To adjust the tension on a drive belt, loosen the adjusting bolt or fixing bolt locknut on the alternator, alternator bracket or tension pulley. Then move the alternator or turn the adjusting bolt to adjust belt tension. Once the desired value is reached, secure the bolt or locknut and recheck tension.

REMOVAL & INSTALLATION

1.5L, 1.6L, 1.8L, 2.0L and 2.4L Engines

Fig. Accessory V-belt routing-Mitsubishi 1.5L, 1.6L, 1.8L, 2.0L and 2.4L engines
Alternator Belt

Fig. Loosen the adjuster lock bolt . . .

Fig. . . . then remove the alternator belt from the engine

1. Loosen the alternator support nut.
2. Loosen the adjuster lock bolt.
3. Rotate the adjuster bolt counter clockwise to release the tension on the belt.
4. Remove the belt.

To install:

1. Install the belt on the pulleys.
2. Rotate the adjuster bolt clockwise until the proper tension is reached.
3. Tighten the adjuster lock bolt and the alternator support nut.

POWER STEERING BELT

Fig. After the adjusting and fixed bolts are loosened, rotate the pump . . .

Fig. . . . then remove the power steering belt from the engine

1. Remove the alternator belt as described above.
2. Loosen the power steering pump adjusting bolts.
3. Remove the power steering pump fixed bolt on the rear of the bracket.
4. Rotate the pump toward the engine and remove the belt.

To install:

1. Install the belt on the pulleys.
2. Rotate the pump until the proper tension is reached.
3. Tighten the adjusting bolts on the pump.
4. Tighten the fixed bolt on the rear of the bracket.
5. Install the alternator belt.

A/C COMPRESSOR BELT

1. Loosen the tension pulley and remove the belt.
2. The installation is the reverse of the removal.

3.0L DOHC, 3.0L SOHC Galant, and 3.5L Engines

Fig. Serpentine belt routing-Mitsubishi 3.0L engines (except 1998-00 Galant models)

Fig. Accessory V-belt routing-Mitsubishi 3.5L and 1998-00 3.0L SOHC Galant engines
ALTERNATOR AND A/C COMPRESSOR

1. Disconnect the negative battery cable.

CAUTION Wait at least 90 seconds after the negative battery cable is disconnected to prevent possible deployment of the air bag.

1. Raise and safely support the vehicle and remove the front undercover.
2. Loosen the tension pulley fixing nut and relieve the tension on the belt by turning the adjusting bolt.
3. Remove the belt.

To install:

1. Install the belt on the crankshaft and alternator pulleys.
2. Using the adjusting bolt on the tensioner, tighten the belt to the desired tension.
3. Tighten the fixing nut to hold the adjustment.
4. Install the undercover and lower the vehicle to the floor.
5. Connect the negative battery cable.

POWER STEERING BELT

1. Disconnect the negative battery cable.

CAUTION Wait at least 90 seconds after the negative battery cable is disconnected to prevent possible deployment of the air bag.

1. Raise and safely support the vehicle and remove the undercover.
2. Remove the alternator and A/C compressor belt.
3. Lower the vehicle and remove the cruise control pump link assembly.
4. Place the power steering hose under the oil reservoir.
5. Loosen the tension pulley fixing bolts and remove the power steering pump drive belt.

To install:

1. Install the power steering pump drive belt.
2. Insert an extension bar or equivalent into the opening at the end of the tension pulley bracket and pivot the pulley to apply tension to the belt.
3. Tighten the fixing bolts.
4. Raise the vehicle and install the alternator and A/C compressor belt.
5. Install the undercover and lower the vehicle.
6. Connect the negative battery cable.

3.0L SOHC Diamante

1. Disconnect the negative battery cable.
2. Loosen the lockbolt on the face of the A/C tensioner pulley.
3. Turn the adjusting bolt of the A/C tensioner pulley to loosen the tension of the A/C belt.
4. Remove the A/C compressor belt.
5. Loosen the locknut on the face of the power steering/alternator tensioner pulley.
6. Turn the adjusting bolt of the tensioner pulley to loosen the tension of the belt.
7. Remove the power steering/alternator belt.

To install:

1. Install the power steering/alternator belt first and then the A/C compressor drive belt.
2. Adjust the belts to the proper tension by turning the adjusting bolts and tighten pulley fixing nut/bolt.
3. Tighten the mounting nut of the power steering/alternator tensioner pulley to 36 ft. lbs. (50 Nm).

Remove the alternator/power steering pump and water pump drive belt to gain access to the air conditioning drive belt.
To remove and install the air conditioning compressor drive belt, first loosen the tensioner pulley lock nut, then turn the adjusting screw to raise or lower the tensioner pulley assembly Accessory Drive - 3.3L Engine or Accessory Drive - 3.5L Engine To adjust the air conditioning drive belt, loosen the tensioner pulley nut and adjust belt tension by tightening adjusting screw. Torque pulley nut to 54 N•m (40 ft. lbs.) after adjustment.
The Poly-V generator/power steering belt has an adjustable tensioner pulley located on the timing belt cover Accessory Drive - 3.5L Engine to maintain proper belt tension. To remove or install this belt, Release tension by loosening the tensioner pulley nut and adjustment bolt Accessory Drive - 3.5L Engine Reverse procedure to install and tighten belt to specified tension.

Locate the two belts on the left side (passenger side) of your Mitsubishi Lancer. The outer belt is a serpentine belt, operating four pulleys and the inner belt is your alternator belt.

2 Follow the serpentine (outer) belt to the three pulleys lined up vertically near the front of the engine compartment. Locate the middle pulley, which is the tension pulley for the belt.

3 Loosen the bolt on the middle pulley with a socket wrench by turning counter-clockwise. Do not remove the bolt, just turn it a couple of times. Loosen the tensioner bolt on the side of the of the pulley, facing the front of the vehicle.

4 Remove the serpentine belt and then loosen the bolt on the alternator. With the alternator loose, move it forward so that the alternator belt loosens up and then remove belt from the pulleys.

5 Install the new alternator belt by placing it over both inside pulleys. Tighten the tension on the alternator belt by moving the alternator back and keeping tension on it by holding it back with a long screwdriver. While the alternator belt is tight, use a socket wrench to tighten up the bolt on the alternator.

6 Place the serpentine belt back on the pulleys and then use a socket wrench on the bolt on the front of the tension pulley. Once the serpentine belt is tight, tighten up the bolt in the middle of the tension pulley.

7 Start the Mitsubishi Lancer's engine to test the alternator belt and make sure it is working properly. Once you have verified it is working, turn the engine off.

IF IT IS ON THE OUTSIDE OF THE OTHER BELTS, ALL YOU HAVE TO DO IS UNBOLT THE TOP OF THE ALTERNATOR, AND PUSH IT IN TO LOOSEN THE BELT FOR REMOVAL! IF IT IS IN BACK OF THE BELTS (ESPECIALLY A SERPENTINE BELT) YOU'LL HAVE TO REMOVE THE SERPENTINE BELT FIRST! THERE WILL BE A TENSION PULLEY HOLDING THE BELT TIGHT! YOU'LL NEED TO USE A WRENCH TO PULL THE TENSION PULLEY TOWARD YOU TO LOOSEN BELT! WATCH HOW YOU REMOVE IT, BCUS YOU'LL NEED TO PUT IT BACK ON THE SAME WAY! THEN REMOVE, AND REPLACE THE ALTERNATOR BELT AS BEFORE, THEN REPLACE THE SERPENTINE BELT!

Locate the two belts on the left side (passenger side) of your Mitsubishi Lancer. The outer belt is a serpentine belt, operating four pulleys and the inner belt is your alternator belt.

2

Follow the serpentine (outer) belt to the three pulleys lined up vertically near the front of the engine compartment. Locate the middle pulley, which is the tension pulley for the belt.

3

Loosen the bolt on the middle pulley with a socket wrench by turning counter-clockwise. Do not remove the bolt, just turn it a couple of times. Loosen the tensioner bolt on the side of the of the pulley, facing the front of the vehicle.

4

Remove the serpentine belt and then loosen the bolt on the alternator. With the alternator loose, move it forward so that the alternator belt loosens up and then remove belt from the pulleys.

5

Install the new alternator belt by placing it over both inside pulleys. Tighten the tension on the alternator belt by moving the alternator back and keeping tension on it by holding it back with a long screwdriver. While the alternator belt is tight, use a socket wrench to tighten up the bolt on the alternator.

6

Place the serpentine belt back on the pulleys and then use a socket wrench on the bolt on the front of the tension pulley. Once the serpentine belt is tight, tighten up the bolt in the middle of the tension pulley.

7

Start the Mitsubishi Lancer's engine to test the alternator belt and make sure it is working properly. Once you have verified it is working, turn the engine off.

Click on the following direct Link. It has several Serpentine Diagrams; one of which matches your specific engine and options (ex: AC/No AC etc).
Regarding HOW:
Standard Rule to Removal the Serpentine Belt:
1. Find the Tensioner(s). (See Diagrams on Link)
2. Using a Serpentine Belt Tensioner Tool, Or Wrench OR Ratchet, Rotate/Move the Tensioner USING THE AVAILABLE NUT OR OPENING (3/8ths or 1/2 inch square opening) away from contact with the belt and towards the area where the belt is not in contact with the Tensioner Pulley. The Tensioner is spring loaded, and is hard to rotate/move.
3. Remove the loosened belt off one of the other more easily accessed Pulleys.
Standard Rules for Installing the Serpentine Belt:
a. Pick a Pulley that is most easily accessed. This will usually be on top. This will be the last Pulley that the belt will go on.
b. Using the Diagram: Install the new Serpentine Belt on the remainder of the Pulleys....over, under, left right.
c. Using a Serpentine Belt Tensioner Tool or Wrench or Ratchet Tool: Rotate/Move the Tensioner Pulley/Arm "away" from Belt contact area on the Tensioner. This spring is pretty hard and with a new belt, it will be even harder to install. Rotate/Move this to as-close to the maximum allowed inorder to have enough slack in the belt to get it up and over the last pulley.
d. Using your other hand - Pull the Belt up and over the Last remaining Pulley.
e. Before releasing the pressure on the Tensioner, visually inspect the remainder Pulleys and the Belts' Positioning on them.
Let me know if this helped...
http://www.2carpros.com/car_repair_information/year/1995/make/chevrolet/model/caprice/1995_chevrolet_caprice_drive_belt_routing_diagram.htm

To loosen the belt look for a pulley that isn't running anything. That is your tension pulley and somewhere either in the center of the pulley or arm the pulley is bolted to there will be a square hole that is the same size as a 1/2" drive socket. Find your 1/2" socket and put it in that hole and either in tightening or loosening position you should be able to move the pulley so the tension on the belt loosens up so you can take it off the pulley. then remove the bolts of the alternator and the wire plug and you got it whipped.

there is an 8mm bolt right under the alternator. loosen that up then loosen the bolt on the idler pulley and itll come right off

The only way to loosen and tighten the serpentine belt is by loosening the alternator and sliding it back or forward. There are TWO bolts that must be loosened, one above, and one below the alternator pulley. A bit of penetrating oil can make things easier.