903 alternator drive belt?

Discussion in 'Rear-Engine Fiats' started by flaviaman, Sep 3, 2018.

  1. flaviaman

    flaviaman Low Mileage

    Portland, OR

    Long time lurker, first post I believe. I have owned my 850 Sport Coupe for 7 years and have gone through the car mechanically, it is a fairly “stock” car. Yesterday I embarked on a 147 mile trip and about 70 miles into the trip the alternator drive belt was thrown / broke. It was a Gates belt with about 2,500 miles on it and about six years old. The belt had a “notched” surface as opposed to a a “smooth” surface. I know the belt was tensioned correctly.

    Any comments? I read in another forum this cars are prone to throwing belts.
    I had been cruising at 5000 rpm for about 35 minutes.

    Ironic to think that out of all the things that can fail on one of these cars it was an American made belt! I have been driven Italian cars for 40 plus years, fist time I have called a tow truck in decades!

    Thanks in advance for any suggestions. 7D1F152A-A0F2-4B08-9D86-66BC724D762D.jpeg
  2. kmead

    kmead Old enough to know better

    I have never thrown a belt on my Sport Coupe so I would not say that it is prone to doing so. I have driven mine for 14 hours pretty much straight at highway speeds when driving from Vermont to Michigan (820 miles) and didn’t throw one.

    Check the alignment of the constituent pulleys or just tensioning if it was just thrown.

    If it broke then its likely an age issue but could have been overtensioned.

    Tensioning can be tricky on these as you need to tension the alternator and then the water pump. If too loose or too tight the belt can be thrown or fail.

    I carry an extra pair of belts, an accelerator cable, clutch cable and some basic tools so I can make minor repairs. I carry the cables as one cannot just find them along the way...
    Last edited: Sep 3, 2018
  3. Jeff Stich

    Jeff Stich True Classic

    Norco, CA
    I've driven hundreds of thousands of miles in my 850's, many of those being highway miles in the 5000-6800 rpm range for many hours at a time (So Cal-Nor Cal runs) without a single belt ever being thrown. I've had 1 (one) 850 belt failure in all my years, which was simply due to its age/use & my own neglect (laziness) in changing it out beforehand.

    Whoever told you that 850's are prone to throwing belts probably has no idea how to correctly set the belt tension. Proper generator/alternator pulley alignment is also critical. The belts don't simply fly off the pulleys by themselves!
    kmead likes this.
  4. NM850

    NM850 True Classic

    Albuquerque NM
    Nice Coupe!
    Hope you get the issue sorted.
    I’ve never thrown a belt but I carry pretty much what Karl carries in every old car I own, from a Land Cruiser to a old F150 to the Italians. Just a product of growing up in the pre cell phone days I guess.
  5. flaviaman

    flaviaman Low Mileage

    Portland, OR
    Thank you for your comments, Jeff and Karl I appreciate your expertise. Your posts confirmed my suspicions....I have great respect for Fiat engineering. I will carry a spare, just in case, in the future.

    Thank you again....

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