Stretch fit belt confusion

[tabijan]

The serpentine belt got shredded at 147k miles. There's enough of the old belt to read FoMoCo CN1Q-6C301-AA FJPBA 6PK 1030 EPDM/PA66 which measures 39-3/4". Shopping on price, I got a Duralast 408K6S 6PK1035S (Autozone) which measures 41". I can put on this belt by hand. It's only a little more snug than a lei. All accessories run at idle and AC works but it looks like the belt will jump off the alternator pulley at any time. Next I got a Gates K060392SF (O'Reilly) which measures 39-3/8". What a bear to install! I can twist the belt 90* between the alternator and AC compressor and between the AC compressor and crank pulley but I wouldn't set a belt that tight with a manual tensioner. I see 405K6 and 6PK1030 belts but there's no mention of stretch fit application. There's a Dayco 6PK1027EE stretch fit (Advance) described to be 41.43" long. I don't know whether to believe the 1027mm part (seems the right spec based on the FoMoCo belt) or the 41.43" part (41" is too long). I can check what the local Ford dealer has tomorrow. Online sources show the part number above as no longer available.

I don't know the history of this car before it got to us so I don't know if the pulleys are original/original diameter.

What belts are known to fit a US spec 2014 naturally aspirated 1.6 with little fuss?

Sixto
2014 SE 1.6 hatchback 147k miles

 

[Handy Andy]

If the belt shredded at 147,000 K or mi whichever, the issue that seems to repeat is with the alternator - you may have to replace the alternator too - the bearings in - or one in it, may have seized (or wobble the pulley out of round) and now drags the newer belts until they too, will shred sooner than later. That drag / action stretches the belt until it'll slide and groove then shred so you're not just looking for a newer belt, to fit. But possibly newer parts that use that serpentine. This includes the water pump using the smooth side of the belt to turn in the correct direction.

The 6PK1030 is the correct perimeter length, 6 groove width - so the "stretch" is belt composition - so look for EDPM to help in the flex and stretch.

 

[tabijan]

Thanks! 6PK1030 specs say it's made of EPDM but description doesn't say stretch application like with other belts.



The first time the belt got on all pulleys, it was two ribs off the alternator pulley. I had to hand turn the engine with a wedge to get the belt fully seated on the alternator and it looked like it was under some trauma getting there. So far so good but I'll keep an eye out for tearing.

Sixto
2014 SE 1.6 hatchback 147k miles

 

[Handy Andy]

Do you have a narrow straight-edge of about 24"? Check the tracking of that belt using that straight-edge or a tape measure for strait-line eyeball measurement "squareness" of pulley aspects to the others - for if the alternator is no longer tracking plumb in line with all the others - you have to locate the pulley that is off - can even be the AC and it's clutch is worn so the pulley it uses is off - in tracking to the others.

This tracking problem is caused by a failure of one part on the serpentine path - which will make others also fail soon enough.