Saturn Belt Tensioner...

if the tensioner is not tightening enough then you either have an incorrect belt or the tensioner itself is worn, if your talking about after replacing the timing belt. if your talking about it being loose and not having been replaced then the belt is worn out. I believe that these have the belt adjuster that is actually the water pump that moves(turns) to tighten the belt.

1. Drain the cooling system until the coolant is below the level of the water pump.
2. Loosen the water pump pulley bolts.
3. Rotate the drive belt tensioner to release the tension on the drive belt.
4. Remove the drive belt from the right idler pulley.
5. Carefully release the drive belt tensioner spring tension.
6. Remove the water pump pulley bolts.
7. Remove the water pump pulley.
8. Remove the water pump bolts.
9. Remove the water pump.
10. Remove the water pump gasket.
11. Clean the water pump mating surfaces.

To install:

Fig. Remove the mounting bolts (3) to remove the water pump (1) and gasket (2).

1. Install the water pump gasket (2).
2. Install the water pump (1).
3. Install the water pump bolts (3). Tighten the bolts to 10 Nm (89 inch lbs.).
4. Install the water pump pulley. Loosely install the pulley bolts.
5. Insure the drive belt is properly centered on all the pulleys except the right idler puller.
6. Rotate the drive belt tensioner away from the drive belt.
7. Install the drive belt to the right idler pulley.
8. Release the tensioner allowing the drive belt tensioner to come in contact with the drive belt.
9. Inspect the drive belt to insure the belt is properly centered on all the pulleys.
10. Tighten the water pump pulley bolts. Tighten the bolts to 25 Nm (18 ft. lbs.).
11. Fill the cooling system.
12. Inspect the cooling system for leaks.

the water pump is under the timing chain cover. if your serpentine belt is loose, that is the belt you can see, then your tensioner is shot. you can buy a new tensioner for about 50 bucks at a parts store. search on www.youtube.com for video directions on how to replace it. if your serpentine belt has not been changed this is a good time to do that as well as it has to come off. replacement of the tensioner and belt is done via a service panel behind the right front wheel.

If you check tension. If it is loose ..over 1/2" freeplay it is too loose. Tighten. If it feels tight. Then the belt is likely dried out and needs to be replaced... Check tensioner to be sure nothing is froze up. Like water pump or tensioner pulley. Check other belts as well.

Has it just started with cold weather? Does it squeal at first then as the engine is revved, stop squealing.

If so its probably your alternator belt has worked loose and needs tightening. I'd check this out first, if you've not done it before ask a friend with some know how for guidance. But as a guide, there should be about an inch of give when flexed on the longest run between 2 pulleys, if more then probably needs tightening. If more than a couple of years old, replace with a new one.

If it still squeals after tightening/replacing, you could have a faulty water pump bearing or pulley bearing. Either would require replacement to pre-empt catastrophic failure and resultant engine damage.

it the belt is loose, the tensioner is bad. Its a pulley that should move and has spring tension on it. its a large pulley about 3" in diameter. replace the belt and tensioner.

REMOVAL & INSTALLATION of timing belt: Fig. 1: View of the timing belt cover
Fig. 2: Loosen then timing belt tensioner using a ratchet and short socket
Fig. 3: Matchmark the direction of rotation of the timing belt
Fig. 4: Once loose, pull the belt off the camshaft pulley

1. Disconnect the negative battery cable.
2. Turn the crankshaft to align the timing belt matchmarks and set cylinder No. 1 to Top Dead Center (TDC) on the compression stroke. Once in this position, the engine must NOT be turned or disturbed.
3. Remove all necessary components to gain access to the cylinder head and timing belt covers.
4. Remove the cylinder head and timing belt covers.
5. There are 2 belts in this system; the one running to the camshaft pulley is the timing belt. The other, shorter one drives the balance shafts and is referred to as the balancer belt or timing balancer belt. Lock the timing belt adjuster in position by installing one of the lower timing belt cover bolts to the adjuster arm.
6. Loosen the timing belt and balancer shafts tensioner adjuster nut, but do not loosen the nut more than 1 turn. Push the tensioner for the balancer belt away from the belt to relieve the tension. Hold the tensioner and tighten the adjusting nut to hold the tensioner in place.
7. Carefully remove the balancer belt. Do not crimp or bend the belt; protect it from contact with oil or coolant. Slide the belt off the pulleys.
8. Remove the balancer belt drive sprocket from the crankshaft.
9. Loosen the lockbolt installed to the timing belt adjuster and loosen the adjusting nut. Push the timing belt adjuster to remove the tension on the timing belt, then tighten the adjuster nut.
10. Remove the timing belt. Do not crimp or bend the belt; protect it from contact with oil or coolant. Slide the belt off the pulleys.
11. If defective, remove the belt tensioners by performing the following:
    1. Remove the springs from the balancer belt and the timing belt tensioners.
    2. Remove the adjusting nut.
    3. Remove the bolt from the balancer belt adjuster lever, then remove the lever and the tensioner pulley.
    4. Remove the lockbolt from the timing belt tensioner lever, then remove the tensioner pulley and lever from the engine.
12. This is an excellent time to check or replace the water pump. Even if the timing belt is only being replaced as part of a good maintenance schedule, consider replacing the pump at the same time. To install:
    
13. If the water pump is to be replaced, install a new O-ring and make certain it is properly seated. Install the water pump and retaining bolts. Tighten the mounting bolts to 106 inch lbs. (12 Nm).
14. If the tensioners were removed, perform the following to install them:
    1. Install the timing belt tensioner lever and tensioner pulley. NOTE: The tensioner lever must be properly positioned on its pivot pin located on the oil pump. Be sure that the timing belt lever and tensioner moves freely and does not bind.
       
    2. Install the lockbolt to the timing belt tensioner, do not tighten the lockbolt at this time.
    3. Install the balancer belt pulley and adjuster lever.
    4. Install the adjusting nut and the bolt to the balancer belt adjuster lever. Do not tighten the adjuster nut or bolt at this time. NOTE: Be sure that the balancer lever and tensioner moves freely and does not bind.
       
    5. Install the springs to the tensioners.
    6. Move the timing belt tensioner its full deflection and tighten the lockbolt.
    7. Move the balancer its full deflection and tighten the adjusting nut.
15. The crankshaft timing pointer must be perfectly aligned with the white mark on the flywheel or flex-plate; the camshaft pulley must be aligned so that the word UP is at the top of the pulley and the marks on the edge of the pulley are aligned with the surfaces of the head.
16. Install the timing belt over the pulleys and tensioners.
17. Loosen the bolt used to lock the timing belt tensioner. Loosen, then tighten the timing belt adjusting nut.
18. Turn the crankshaft counterclockwise until the cam pulley has moved 3 teeth; this creates tension on the timing belt. Loosen, then tighten the adjusting nut and tighten it to 33 ft. lbs. (45 Nm). Tighten the bolt used to lock the timing belt tensioner.
19. Realign the timing belt marks, then install the balancer belt drive sprocket on the crankshaft.
20. Align the front balancer pulley; the face of the front timing balancer pulley has a mark, which must be aligned with the notch on the oil pump body. This pulley is the one at 10 o'clock to the crank pulley when viewed from the pulley end.
21. Align the rear timing balancer pulley (2 o'clock from the crank pulley) using a 6 x 100mm bolt or rod. Mark the bolt or rod at a point 2.9 in. (74mm) from the end. Remove the bolt from the maintenance hole on the side of the block; insert the bolt or rod into the hole. Align the 2.9 in. (74mm) mark with the face of the hole. This pin will hold the shaft in place during installation.
22. Install the balancer belt. Once the belts are in place, be sure that all the engine alignment marks are still correct. If not, remove the belts, realign the engine and reinstall the belts. Once the belts are properly installed, slowly loosen the adjusting nut, allowing the tensioner to move against the belt. Remove the pin from the maintenance hole and reinstall the bolt and washer.
23. Turn the crankshaft 1 full turn, then tighten the adjuster nut to 33 ft. lbs. (45 Nm). Remove the bolt used to lock the timing belt tensioner.
24. Install the lower cover, ensuring the rubber seals are in place. Install a new seal around the adjusting nut, DO NOT loosen the adjusting nut.
25. Install the key on the crankshaft and install the crankshaft pulley. Apply oil to the bolt threads and tighten it to 181 ft. lbs. (250 Nm).
26. Install the upper timing belt cover and all applicable components. When installing the side engine mount, tighten the bolt and nut attaching the mount to the engine to 40 ft. lbs. (55 Nm) and the through-bolt and nut to 47 ft. lbs. (65 Nm).
27. Connect the negative battery cable.

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For water pump removal and installation contact me:

1. Remove all necessary components for access to the timing belt cover, then remove the cover.
2. Rotate the crankshaft clockwise and align the timing marks so No. 1 piston will be at Top Dead Center (TDC) of the compression stroke.
3. Loosen the tensioning bolt and the pivot bolt on the timing belt tensioner. Move the tensioner as far as it will go toward the water pump. Tighten the adjusting bolt.
4. Mark the timing belt with an arrow showing direction of rotation.
5. Remove the timing belt.
6. If defective, remove the timing belt tensioner.
7. Align the timing marks of the camshaft sprocket and check that the crankshaft timing marks are still in alignment.
8. If removed, install the timing belt tensioner, spring and spacer with the bottom end of the spring free. Tighten the adjusting bolt slightly with the tensioner moved as far as possible away from the water pump.
9. Install the free end of the spring into the locating tang on the front case.
10. Position the timing belt over the crankshaft sprocket, then over the camshaft sprocket. Slip the back of the belt over the tensioner wheel.
11. Turn the camshaft sprocket in the opposite of its normal direction of rotation until the straight side of the belt is tight and be sure the timing marks align.
    NOTE If the timing marks are not properly aligned, shift the belt 1 tooth at a time in the appropriate direction until they are aligned.
    
12. Loosen the tensioner mounting bolts so the tensioner works, without the interference of any friction, under spring pressure. Be sure the belt follows the curve of the camshaft pulley so the teeth are engaged all the way around. Correct the path of the belt, if necessary.
13. Tighten the tensioner adjusting bolt, then the tensioner pivot bolt to 15-18 ft. lbs. (20-26 Nm).
    NOTE Bolts must be tightened in the stated order or tension won't be correct.
    
14. Turn the crankshaft 1 turn clockwise until timing marks again align to seat the belt.
15. Loosen both tensioner attaching bolts and let the tensioner position itself under spring tension. Retighten the bolts.
16. Check belt tension by putting a finger on the water pump side of the tensioner wheel and pull the belt toward the water pump. The belt should move toward the pump until the teeth are approximately 1 / 2 of the way across the head of the tensioner adjusting bolt. Re-tension the belt, if necessary.
17. Install the timing belt covers and all other related components.
    

A loose belt is usually the result of a tensioner that is going bad. Check the tensioner, if you can move it with your hand it's time to replace it. The tensioner is designed to keep the belt tight as it get's older and stretches.

Disconnect battery earth lead. Do not turn crankshaft or camshaft whn timing beld removed. Remove spark plugs to ease turning engine. Turn engine in normal direction of rotation (unless otherwise stated) Do not turn engine via camshaft or other sprockets. Observe all tightening torques. Remove engine, remve RH engine mounting. Remove auxiliary drive belts, water pump pulley, crankshaft pulley, timing belt upper cover, timing belt lower cover. Turn crankshaft clockwise to TDC on No. 1 cylinder, slacken tensioner bolts 5 & 6. Move tensioner away from belt and lightly tighten bolts. Remove timing belt. Remove water pump and replace with new one. Suggest to replace cambelt as well.
Installation
Ensure timing marks aligned3 & 4. Fit timing belt in anti-clockwise direction, standing at crankshaft sprocket. Ensure belt is taut between sprockets on non-tensioned side. Slacken tensioner bolt 5. slacken tensioner bolt 6. Allow tensioner to operate. Tighten tensioner bolt 6. Tighten tensioner bolt 5. Turn crankshaft on turn clockwise. Ensure crankshaft sprocket timing marks aligned 4.
Slacken tensioner bolt 5. Slacken tensioner bolt 6. Allow tensioner to operate. Tighten tensioner 6. Tighten torque: 20 - 26 Nm. Tighten tensioner bolt 5. tighten torque: 20 - 26 Nm. Apply thumb pressure to belt at middle. Approximately 5kg. Belt should deflect to 1/4 of tensioner bolt head width 7. Belt tention can also be set using burroghs (BT-33-73F) tension gauge 10 at middle. Turn crankshaft 90 ° anti clockwise. Check belt tension is 9.5 16,5kg (engine must be cold). Install components in reverse order of removal. Fit cranckshaft pully. Tighten crankshaft pully bolts 8. G4-J: Tightening torque: 12-15Nm.
G4-N/G4-k: Tightening torque: 10-12Nm
G4EA: Tighten crankshaft pully bolt 9. Tighten torque: 140-150Nm.