Fan belt twisting why?

[Nulla]

Pls see picture below, the alternator fan belt are twisting on the crankshaft pulley, i have tried different tensions on the belt but they keeps twisting on the groove of the pulley. These are OEM pulleys. I have included part number of the belts. They are brand new. What would cause this? Thx

 

[sk66]

Usually a pulley that is too shallow...

 

[Growlerbearnz]

Loose belts? A belt should deflect about 10mm when pressed with your thumb from below.

Check that all 3 pulleys are aligned: twisting belts can also be due to offset misalignment as below. (Angle or twist misalignment is almost impossible, but would be very impressive!)



Do you have the stock alternator? If you've installed an aftermarket alternator (particularly an upgrade that wasn't originally intended for the 4D56) it might be out of alignment with the crankshaft and waterpump pulleys.

Sometimes the outer ring of the crankshaft pulley becomes separated from the inner piece. It looks to be in the right place in your photos, but just check it anyway: with the engine running check that the crankshaft pulley doesn't appear to wobble.

Belts that have been savagely levered onto the pulleys when installing can be damaged internally and prone to flipping.

Last thing: once you've diagnosed and corrected the fault, be aware that belts that have flipped once can be prone to flipping again. Keep the belt tension correct and check the belts often.

 

[Nulla]

Usually a pulley that is too shallow...

Loose belts? A belt should deflect about 10mm when pressed with your thumb from below.

Check that all 3 pulleys are aligned: twisting belts can also be due to offset misalignment as below. (Angle or twist misalignment is almost impossible, but would be very impressive!)

View attachment 13224

Do you have the stock alternator? If you've installed an aftermarket alternator (particularly an upgrade that wasn't originally intended for the 4D56) it might be out of alignment with the crankshaft and waterpump pulleys.

Sometimes the outer ring of the crankshaft pulley becomes separated from the inner piece. It looks to be in the right place in your photos, but just check it anyway: with the engine running check that the crankshaft pulley doesn't appear to wobble.

Belts that have been savagely levered onto the pulleys when installing can be damaged internally and prone to flipping.

Last thing: once you've diagnosed and corrected the fault, be aware that belts that have flipped once can be prone to flipping again. Keep the belt tension correct and check the belts often.

I re installed the pulleys that came with the rig when i first got it, they work fine. The new pulleys looks very little bit wider. FYI the NAPA pulleys pictured below where making noise when the engine is cold that is the reason i replaced them. The Bando RAF 2430 works i need to find a spare. Thx

 

[sk66]

I re installed the pulleys that came with the rig when i first got it, they work fine. The new pulleys looks very little bit wider.

Too wide is basically the same as too shallow; the belt rides on the narrow part and can roll. Other things can cause it (very loose belts, etc), but width/depth mismatch is most common IME... they can be surprisingly fussy things.
I believe the NAPA belts have a slightly different taper/angle which makes them problematic (tension/noise).

 

[Growlerbearnz]

the pulleys that came with the rig ...The new pulleys looks ... the NAPA pulleys pictured below...

Do you mean "belts"? All I see in the pictures are belts.

 

[Nulla]

Do you mean "belts"? All I see in the pictures are belts.

yes i meant belts, sorry

Too wide is basically the same as too shallow; the belt rides on the narrow part and can roll. Other things can cause it (very loose belts, etc), but width/depth mismatch is most common IME... they can be surprisingly fussy things.
I believe the NAPA belts have a slightly different taper/angle which makes them problematic (tension/noise).

yes i tried making the Napa belts work by adjusting them but i could not get rid of the noise they make when the engine is cold the noise is louder when the temperature out side is cold.

thx both for your help.

 

[Growlerbearnz]

The Napa belts appear to be the toothed kind: they will cause trouble if any of your pulleys are worn.

I've added a FAQ on belt squeal here which should explain it.