Serpentine Belts

Why does your serpentine belt keep coming off the pulley?


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2009-11-15 21:33:03
2009-11-15 21:33:03

Your serpentime belt tensioner needs replacement ( spring inside it broken/weak) or your belt worn , Have you changed any components lately ? installed right ( pulley not centre with rest of system ) ( shims )


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A serpentine belt has an idler pulley on is to keep it tight at all times. If your serpentine belt is loose, then something is worn out. Its possible the idler pulley is stuck in its bracket so it cannot move or the spring on it is worn out.

If it is a serpentine belt the idler pulley more than likely needs replacing. If it is a drive belt you are adjusting it too tightly.

A bad pulley (sharp edge) A seized pulley A misaligned pulley

Serpentine belts use an pulley to keep tension on the belt. You need a breaker bar; attach to the tension pulley and turn the nut. One way will not move and the other way will loosen the belt. It will usually then just slide off that pulley and then come off all the rest.

If it is a serpentine belt the idler pulley more than likely needs replacing. If it is a drive belt you are adjusting it too tightly.

Your belt is either to big or just plain worn out.

Several reasons come to mind. Misaligned pulleys .Knife edge , bent or damaged pulley. Incorrect belt tension. Belt contact with protruding part. If it is a serpentine belt the idler pulley more than likely needs replacing. If it is a drive belt you are adjusting it too tightly. The AC compressor (if equipped) could be locking up also.

Check to see if the cowl drain tube over the belt is disconnected. If it is the rain water running out pours directly onto the serp belt and can cause the belt to slip off.

The serpentine belt and the tensioner on a 300 SE motor is part of the fan system that controls all of the smaller motors on the front of the engine. The serpentine belt helps turn the alternator, power steering pump, water pump, and the fan. The tensioner is a pulley on this belt that helps to keep the belt tight enough to stay on, but not too tight to hinder operation.

Just to get it off? Try using a single edge razor blade. It will have what is called an idler pulley probably, most do, This pulley serves only one purpose, to keep the belt tight. This pulley can be levered, probably to a slack position, usually downward and the belt can then be removed.

Something is out of line, or you are using a warped belt. Take off and check the idler and also the tensioner pulley. They are most likely to cause belt problems.

Most likely causes would be a pulley that is locking up, a misaligned pulley, or something getting on the belt causing it to fall off. Check the ac compressor and water pump.

The serpentine belt can be replaced easily by removing the supercharger pulley first than pulling the serpentine belt off completely now that is is loose. Once you pull of the supercharger pulley than the entire belt can be pulled off quite easily and replaced. Installing the serpentine belt is opposite of removal. Just put some weight on the pulley as you press it down on the serpentine belt when reinstalling the belt and pulley than slide it back on the slide bolt holder. You will know what to do at this point. Than install the bolt and the job is done. It takes about 15 minutes to replace the belt if you are good. Otherwise it may take up to an hour if you lack some muscle to push the pulley down over the belt in order to slide it back on. The same approach works for the AC belt but you need to remove the AC pulley which is right next to the AC compressor. This pulley near the compressor does have a history of squeeling since it is close to the ground and gets a higher does of road water after driving through puddles. It needs to be replaced every 5 years or so. Just keep that in mind. I have found this approach to be the fastest and most efficient way of replacing the belt. Dave (Las Vegas)

The most common cause for a belt coming off is the belt tensioner is worn out. When this happens, the belt is not alighned with the other pulleys I.E. Power steering, A/C compressor, water pump.

To remove the serpentine belt use a 1/2" breaker bar to rotate the tensioner upward off the serpentine belt while removing the belt from the pulleys. When installing the new belt make sure the belt is aligned properly in the grooves of the accessory pulleys(or the costly new belt will be shredded when the engine starts). Install the serpentine belt under the tensioner pulley by rotating the tensioner upward with the 1/2" drive breaker bar. When the breaker bar is released the tensioner will keep the belt properly tensioned.

Chrysler has a belt and pulley kit to fix the problem. it removes the smooth surfaced pulleys and replaces them with grooved pulleys. the new belt is grooved on both sides

All serpentine belts have two pulleys that are not attached to a driven device. One is the idler pulley (re-directs the belt) and the tensioning pulley (spring loaded as to keep the belt at optimum tension regardless of all other pulleys). It is the tensioning pulley that you manipiulate to remove the belt. There will be a 1/2 inch "hole" or indent into which you place the socket tip of a ratchet handle. When you torque the handle in the proper direction you will compress the spring, loosening the pulley! All very simple. The tensioner is loosened by lossoning the nut on the front of the pulley, and turning the forcing screw coounter clockwise.

This is really a pretty easy repair. The idler pulley maintains spring tension to keep the belt tight. You will probably find a square hole in the hub assembly of the idler pulley. You can fit your 3/8" rachet directly into the hole, then with only a little force, be able to rotate the pulley in the direction that pulls it away from the serpentine belt. Remove the belt while holding rotational force to the idler pully. Once the belt is off, you can slowly release tension, until your ready to reverse the operation for fitting up the new belt.

It's function is to keep the tension on your serpentine belt at the correct tightness. On most vehicles you will need to take the tension off in order to change the serpentine belt. On many vehicles this is accomplished by placing a socket and ratchet (usually 1/2 inch will be required) on the bolt on the end of the pulley. By using the ratchet you take the tension off enabling you to remove the belt. To place the new belt on just repeat the process enabling you to slip the new belt in to place on the pulley. For proper belt arrangement most vehicles have a diagram under the hood in the engine compartment.

It could be a loose serpentine belt. Or if the alternator is going out either way its most likely a charging problem.

no it is a belt it fits onto a pulley and enables your fan to turn to keep your engine cooled.

Yes. There is a spring loaded arm attached to the block (or head) to keep tension on the serpentine belt. You can tell which pulley it is because it will have a fairly long hex-shaped spindle in the middle (for putting a wrench on to better relieve the tension). Look for a pulley with nothing much behind it.

The Pulley is slipping forward during pump engagement and tightening the belt to breaking point. Tighten or replace bolts holding power steering pump to the bracket. I have been hearing a pulley that sounded loose or like it was gonna fail and have been waiting on the serpentine belt to break on 1996 Mazda protege. Will I feel that the pulley is slipping?

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