Belt came off

Thought I'd better join this forum, since I've had this 2008 V6 4x4 for a little over six months now.
No real issues with the motor until yesterday, had the belt come off and didn't notice until I turned and had no power steering. It was a sunny day and I didn't see the battery icon lit, either. By the time I noticed this the temp gauge was on H. I had driven for less than 15 minutes at the most.
Pulled over, and found coolant had spilled out of the reservoir not too much. Truck was still running (I thought it had stalled, but no).
Anyway, belt was a Continental brand, and had one rib hanging off. I'm guessing the rib got under a pulley and threw the belt. Got a new Gates belt today, but was worried about how hot the motor got.
My old truck (Ford) has failsafe cooling (which works well, btw). Wondered if the Toyota has something like that, wasn't sure.
I did not see a check engine light, and so I scanned for codes, none found.
I'm assuming that if the truck was dangerously hot I'd have a PO217 stored. No codes were found.
Fortunately it runs fine (I had put the old belt on to get it home a short distance),
Thanks for any input.

 

Check the idler pulleys, tensioner pulley, A/C and alternator pulleys for proper action before putting the belt on. The idler/tensioner pulleys I particular should have a small amount of resistance rather than spin freely; a lack of grease makes them sound like old time metal skate wheels which is a sign they’re on the path to failure. Unlikely that would cause your belt to come off, more a case of “as long as you’re in there, get the associated work done”.

 

My 08 Sport threw a belt about a year ago, but it was caused by the alternator pully bearing failing. They can just break from age/fatugue, but it's more likely that something else is going on with one of the accessories in the system. Double check everything to confirm there's nothing else going bad that would cause the belt to come off.

 

Thanks.
Yeah, everything seems fine, all the accessories turn smoothly with no play. I've never had a serpentine belt fail ever, and have owned cars with this type of belt for close to 40 years.
My main concern is that I didn't overheat the engine. My old Ford would go into limp mode (had a clogged radiator once). I think it threw a code, too. Not sure if Tacoma is set up that way or not. Hope so.
Thanks again.

 

2nd gens have no overtemp protection other than disabling the A/C, since you didn't lose the coolant it will probably be ok. If it had been driven any length of time with no coolant that's when damage can occur very quickly.

 

Thanks, it just lost a few ounces out of the overflow.

 

How many miles on it?

 

Check the crank pulley. Mine threw a belt and it took me two belts to find out the crank pulley was shot

 

Truck has just over 300k miles on it. Runs really good, I'm very impressed with the 4.0L motor. I'm used to Ford and Mitsubishi (oil using engines). Toyota uses almost none between changes.
What goes wrong with the crankshaft pulley? Mine looks fine.
Never mind, I see it incorporates the harmonic balancer. Let me check for wobble.

 

The crank pulley is the same as the harmonic balancer. The rubber deteriorates and the pulley will wobble and throw the belt

 

I checked it and it's nice and true, no wobble at all. Guess it was either water or the one belt rib caused it to fly off.

 

I think I found the cause of the belt failure....
Drove to work, noticed what sounded to me like a slight ping or tick. Stopped tonight and revved motor while parked and found it's the new belt slipping.
I'll order idlers and tensioner I'm thinking weak tensioner spring.
Thanks for all the replies, much appreciated!

 

When you actuated the tensioner to put the new belt on, how hard was it to move? I found mine was quite tight when I replaced the pulleys (just did the bearing in the tensioner pulley since tension was good IMO).

The tensioner comes as an assembly and you'll need to unmount the alternator and A/C compressor to replace it (but you can just move them out of the way). Many report it's a pain in the rear to do. Do search the forums for one of the threads that discuss it. Here's one with a few pictures of the process.

 

The tension felt adequate to me, but I'm just guessing it's weak, since the belt can slip enough to chirp sometimes when the motor is revved.

 

It certainly could be the case. I was just thinking on the other hand, if one of the accessories is putting a lot of extra resistance on the belt, even a properly tensioned belt will slip. Double-check the water pump, alternator, A/C and power steering before committing to replacing the tensioner. I know I'd hate to go to all that trouble and find out my problem was still there.

 

Will do, thanks!. I'll have to wait until Friday to check it, but will post results. Thanks again.

 

Just a personal anecdote. When I replaced the idler pulleys, tensioner bearing, and belt, I had done a check of all of the accessories and they felt fine. Then a few weeks later, my alternator bearing completely siezed up after sitting in my driveway for a couple of days. Totally fried the belt. Belt tension was fine, though!

 

Just checked - I lost exactly 12 oz of coolant when I had the belt come off. Going out to check the pulleys and idlers and see where the squeak is coming from.

 

Changed the belt from a Gates to Bando, and noise went away. But I wasn't sold, since Gates makes a good belt. Turns out, the tensioner arm is damaged and not true with the rest of the pulleys. It was a little tough to see at first. When I move the tensioner to release the belt, the arm moves to where it should be, and then the spring tension is relieved. It's crooked, is the best description, and putting tension on it pulls it square with the rest of the pulleys and idlers.
So I'll be replacing the tensioner. That also explains why the first belt failed.

 

I'm about to swap the tensioner, can anyone provide the torque specs for the bolts? Thanks!