If the belt is melting, it's due to too much friction on/at the bearing. Which seems to either indicate a bad bearing, or too much tension (perhaps leading to some sort of situation in which you're putting lateral stress on the bearing, leading to it dragging.)
You would think, but it isn't a bad bearing causing this particular tendency. Too much tension, perhaps. Certainly a bad bearing CAN contribute but it just is not what I have experienced or have the other owners I have spoke with over the past 20 years. I stood in Bentrm's shoes three times, maybe four, the first decade I owned my 308. Fortunately for me the belt would snap off while I was in town (and once in my driveway). Each time I scrapped melted rubber off the pullies with a screwdriver Anyway, I last melted and popped a belt about 12 years ago. Once the two belt set up was installed it hasn't happened since and the wp is the same and I only removed the alt 2 years ago for a rebuild because it was getting tired. I believe it was the original. So if it were bad bearings, at least in my case, they would have revealed themselves at some point since 2005. They haven't. But remember, the SB I posted tells us the cars were doing this when they were relatively new and frequently enough for Ferrari to intervene with a two belt upgrade kit.
I am sorry but I disagree. My take, not enough tension. I know, I know! Again, my car. My specific car. My method worked. Tight belt. I love this forum, I love this discussion. Again, this happened after my self-done belt service. After searching the data base on this forum, I did find a procedure. It was a way to tighten the belt; basically, torque this first, then this, then this... I tried that. I love "as per manual" stuff. Nope. Dint work. Wood shims to increase tension. Result. For what it's worth, I also searched the Mondial forum. I purchased a belt that a member experimented on. Now i'll search to find that thread. BEST HELPFUL AREA ON THIS SITE! REAL PEOPLE HERE! THANK YOU ALL! Now, tighten your belt with wood shims! UHHHHH Ohhhh!
As Spicedriver advised - get a Krikit belt tensioning gauge. Then you will be able to rule out belt tension as an issue on the next belt you install. I've used mine for years, and - so far - NEVER had any belt slippage, failure, or bearing damage, on any car. I just rebuilt the water pump in my 328, and found my first ever mechanically failed thermostat. The staked brass tabs had cracked and broken off, allowing the thing to just fall loose and clank around in the housing. Of course, I wonder what became of those little brass pieces that broke off? Surely they're wedged in my radiator core or something, where [hopefully] they won't do any real harm... But that makes me wonder if you might not have something interfering with your pump's impeller, that makes the pump turn slowly or even stop turning intermittently, while the bearings are fine? For example, my broken thermostat was too big to fit down there and interfere with the impeller rotation, but a small piece of it might have done so... a small metal piece, if it found its way to the gap between the impeller and pump housing, I'd imagine might slow the impeller, leading to belt slippage... I imagine you've ruled out ice as the potential culprit, but ice can definitely jam or impede the impeller's rotation, and then, when you take it apart after the belt is melted, the ice is also melted, leaving no sign that it was ever there... Another experience when I was a beginner mechanic: I had liquid spill onto the belt and pulley, which lubricated it enough to cause the belt to slip, which repeated even after replacing the belt, even after carefully cleaning all the pulleys the belt touches, to remove any trace of the coolant, before installing the new belt.... turned out that it wasn't even coolant that caused that one, but oil that had dripped onto the belt/pulley, which not only lubricated the belt/pulley system, but also reacted with the rubber of the belt, lowering its melting point, so that it failed at a much lower temperature. I know this because it happened again, the next time Jiffy Lube changed the oil! Final thought: maybe something other than friction is heating the pulley, melting the belt? For example, if hot gas were flowing onto the pulley, maybe it could get hot enough to melt the belt, even without any slippage at all? Anyway, just a couple of other possibilities that I didn't see in the thread, so I wanted to offer them, in case they might jar your diagnostic thinking in a different direction.
Yes! Love this place! I wanted to suggest a belt tension gauge. Also, I may have gotten some fluid on the pulleys or the belt.
Yinz need a break. Here's a pic of my newly acquired beverage dispenser. Image Unavailable, Please Login
I had issues with my single water-pump-belt system - the belt would 'melt' itself into a hard-plastic donut around the pulley. There was zero issues with my water pump - the belt would smoke/fail after sudden let-off on the throttle. All belt issues were caused by something coming into contact with the belt, and causing it to 'drag', and friction did the rest. Several failures were traced to the A/C compressor not having the correct washers/spacing to 'clear' the belt, causing the slack to contact the bracket. The last failure was an errant hose route during a service, causing the belt to saw through the hose and melt itself. Again, no issues with the water pump or alternator, as both had been professionally rebuilt.
