Had an exciting moment on the highway this weekend when the water pump / alternator belt snapped. Everything turned out OK, no engine damage, only spoiled plans. Belt was a Dayco top-cog, no more than 5 years old. I did recover the belt which was flung up into the engine compartment and it had clearly just plain wore out, rather surprising given the age and limited mileage. Has numerous cracks in the rubber along the top side.
Megasquirt 3 is always recording to SD card which gives a glimpse of how quickly things go down (or up, rather). Figured a few people might find this interesting:
Ambient temp: About 85F, sunny, humid, AC on full.
From the moment of belt loss (battery suddenly drops 2v, the exact point is pretty obvious) there was no measured temp increase for 30 seconds at the Y-pipe.
After 30s, temperature increase 1.5 degrees F per second. I'm guessing that it took a little time for coolant to circulate by convection which is why there was such a long delay.
Dash gauge read 260 when I was finally safe to engine-off.
I boiled away about 1.5gal of coolant/water in 80 seconds.
I'm sure the charge light came on but I didn't notice it, being red and right about behind where my hand is on the wheel. I did notice the abnormal gauges (high temp, low volts) but the 2nd half of the game had already begun.
I carry a tool kit & spare belt, but had never actually used those tools to change a belt. A magic "all in one" type wrench that seemed useful on paper could not fit between the engine bay wall and the bolts locking the AC belt tensioner. I cut the AC belt off so the water pump / alternator belt could be installed which was not ideal. A stock-style alternator tensioner is not an easy affair to work when you're on the shoulder, and the shoulder quickly transitions to a drainage ditch. Once cooler, was able to drive the car in surges to a weigh station 1 mile up the road and at least get off of the shoudler. Given more time I may have been able to work out a solution to release the AC belt but traffic passing at 80MPH only a few feet away, plus I had one of my kids with me, and the problem called for a more rapid solution.
Lessons learned:
-If you lose this belt you have at minimum 30 seconds to "find a landing spot"
-250F+ is a scary number to see but absolutely no damage resulted
-Water boiling stirs up crud, consider a full-flush if this happens (currently in progress)
-If you carry spare parts, check that your tools are actually useful to install them
-Consider a turnbuckle type alternator tensioner instead of stock
A stranger stopped to help, assuming it was a fire given the cloud pouring from the engine bay and came running with a fire extinguisher. He also drove up to the nearest exit to bring back water. Good people are out there!