Does this make sense? Last night, after a 1 hour highway trip, the alternator belt on my 87 4R (22-RE) snapped less than a mile from my home. Although maybe I should have, I didn't think twice about driving the rest of the way home. Nor did I notice anything beyond the Check Engine and Brake warning lights on the dash. I figured running off the battery for that short a distance would not be a big deal. However, when I pulled into my driveway and parked, I heard the radiator boiling and saw that some coolant (not much) was spilling out of the overflow bottle. I'm guessing now that the alt belt must also power the water pump. Frankly, I didn't notice whether the temp guage, which had read slightly less than half on my highway trip, shot into the red on that last mile. I wish I had bothered to look. First, does the alt belt in fact drive the water pump? And how likely was it that I could have done damage to a hot engine in that short mile? For what it's worth, this morning there was no sign of oil in coolant, or vice versa. Any opinions would be most welcome.

H.
95 4R
87 4R
Bethesda, MD

 

Yes, the alternator belt is also the water pump/fan clutch belt. And if you dorve it that far, and it got that "warm", then you've trashed the hg, and probably cracked the head as well. You may not notice any immediate symptoms. When my friend did that to mine, and didn't bother to tell me, it took a couple of months before things really started to go to heck, and then they went downhill fast. I would pull the head immediately, replace the hg, and take the head to a shop and have it checked for cracks or warpage. I'll wager you've got both. Also, make sure that you change the oil and flush the cooling system. May be a good time for a new thermostat, as when they overheat, they sometimes lock wide open as a "failsafe" feature.

 

For what it's worth, I decided not to panic and tear down the engine without waiting for signs of a problem. I replaced the belts and the thermostat and all appears to be fine. No signs of any coolant loss, or any oil-coolant mixing. No sign of condensation under the oil cap. I've run the truck in heavy traffic with the a/c on high and, as per usual, the temperature guage reads just below half. I may have lucked out and avoided a real problem. And now I know that when a belt breaks you should shut the engine down immediately. Lesson learned.

H.

 

Just wait. You'll start loosing power. Then blowing water out of the recovery tank. Just a little bit at first. Maybe just getting the tank a little fuller each time you run it. It'll start running warmer and warmer. And then the funny noises start.
I'd put money on the failed head gasket and warped head. Just give it time. These Toyota motors are awfully forgiving, and will let you know, usually, when they're failing. They're incredibly tough too, but they do have their foibles.
Start saving up for the new head and top end gasket set. I would if I were you. I'm NOT you, but I would start saving now.
Or, as the saying goes, "You'll be soooorrryyyyy!" (probably)

 

I ran my 22RE on my 91 pickup hotter than that by accident and it was fine. You might be lucky.