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Thread: Screwy serpentine belt

  1. #1
    Join Date
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    Icon5 Screwy serpentine belt

    Heya Dori-Kaze, first post here. Wish it would have been about nicer things but I'm in desperate need of help.

    I recently was on a road trip and snapped my alternator/water pump belt on my 85 aw11. I had heard belt squeal/smelled burning for a few days before but decided to ignore it since I was on vacation and couldn't do anything about it. I knew the belt was old and just hoped it would hold for a while longer. Anyway, I had the belt replaced while stranded in a little town, only to have it snap off again 30km down the road. Before the new belt was put on the pulleys were checked and they spun freely. Belt looked straight and wasn't overtightened. The only thing that was off was the engine cranked/started hard right after the belt was put on. After that it ran perfectly till the snap (didn't hear anything cause header dump but there was no smell). 30 smooth kms going at 130 later, belt snaps going up a little hill at 4k rpm. It was completely shredded/layered. Had it towed, went over the pullys again and they still spin freely. Nothing seized. Again, nothing looks wrong. I'm completely stumped and need help since my trash is 350km away from my house in the middle of nowhere. Belt was ordered from Napa, was for my car and fit well so it shouldn't be that.

    Any help is appreciated!

  2. #2
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  3. #3
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    Quote Originally Posted by Jehuty77 View Post
    Perhaps the belt was just overtightened
    I was considering that, but when it was installed there was a finger width of slack on the belt. Worse comes to worse I'll just run up another belt and drive around a bit stopping intermittently to see what's happening. Is it possible that something is seizing up/not rotating correctly at higher rpm or when things warm up? I heard somewhere that alternator bearings can do that. AHHHH

  4. #4
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    Check the pulley alignment. Also is there worries about the crankshaft thrust bearings? if the crank was walking it could do weird things to the belt.

  5. #5
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    have a tech inspect the pulleys for pulley line and run-out, or other damage to the pulley. A ding or dent on the pulley will shred a belt. Also, use genuine toyota belts. They're the same price as aftermarket replacements, but tend to be thicker, stronger, and more durable
    - Brian


  6. #6
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    Quote Originally Posted by Sparkie View Post
    Check the pulley alignment. Also is there worries about the crankshaft thrust bearings? if the crank was walking it could do weird things to the belt.
    The mechanic friend where I have the car sitting now also says it might be crank walk. He's going to put it up on the lift later and give it some revvs and see if there's any lateral movement. I doubt it though.

  7. #7
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    The crank pulleys have a habit of separating. The pulley portion can walk on the balancer.
    1JZ 1984 Celica GTS
    1UZ 1981 Corolla sedan
    ? 1972 Celica race car

  8. #8
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    Quote Originally Posted by clay72 View Post
    The crank pulleys have a habit of separating. The pulley portion can walk on the balancer.
    Hmm, how could I check for that? If that's the case I'd just replace the crank pulley, right? Sorry if this is obvious, I'm a bit inexperienced

  9. #9
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    The easiest way to check the pulley is to bring number 1 clylinder up to TDC, by placing a rod down the plug hole and crank the engine by hand until the piston is at the highest point. Then check to see if the timing mark on the pulley is aligned correctly. If not then the outer ring on the pulley is walking. You could also probably see cracks in the rubber bonding between the inner and outer section of the pulley.
    I would not rule out bad bearings on alternator. Use a long screw drive against the alternate case, while you have your ear against the screw driver. If the bearings are shot, you should be able to hear them rumbling. Dave W

  10. #10
    Join Date
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    Quote Originally Posted by clay72 View Post
    The crank pulleys have a habit of separating. The pulley portion can walk on the balancer.
    This isn't popular on the 4AG but I have seen it on occasion. As for engine bearings, the rod bearings do get knocky, haven't seen failed thrust bearings yet.

    To check, simply remove belts and pry on the crank pulley to see if the outer portion moves relative to the inner.
    - Brian


  11. #11
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    I had it happen once... now i can't remember if it was a 4age or a 3vz though. It never walked enough to hurt a belt, but it did slip on the balancer.

    Yeah, just pop the belt off.

    maybe it was a 4AC?
    1JZ 1984 Celica GTS
    1UZ 1981 Corolla sedan
    ? 1972 Celica race car

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