HELP: Just started 4.0L SOHC, threw the serpentine belt

[roboman]

I just went out to start my 99 4.0L SOHC and heard a clunk as it first cranked. The engine started and sounded like normal, but the battery light came. I popped the hood, and the belt was thrown inside. I also found a purple spring underneath the car (pictured). I think I see where the spring came out. It looks like it's out of either the starter or the alternator, but I'm not quite familiar enough with the truck to tell - staring at the Explorer face on, the thing is on the left side attached to the belt drive line. And NOW, there is a pretty constant drip coming from the bumper. It looks like it's just rain water, which is very possible since we got pounded yesterday, but it started after all this happened which is throwing me for a loop. Please help since I am kinda in a bad spot right now! More info can be posted if needed.

 

[jremington59]

I'm guessing your belt tensioner broke.

 

[drdoom]

I agree.

 

[Sedition]

Yep, that is the spring that is supposed to be inside your serpentine belt tensioner. I'd say it has exploded on you, unfortunately.

My tensioner is about to explode also, they go for about 40 bucks online.

 

[roboman]

Yup, update: I found the tensioner sitting in the engine bay. So my question is how the hell did it pop off?? The bolt and washer that mount the tensioner to the engine are still snug so it's not like those were loose. The belt is also fully intact and doesn't show any signs of wear. It does look worn around the tensioner where it popped off, though, perhaps slowly over time. So what do I do next? Should I buy a new one or is the old one salvageable? And is this a job that a light-duty, learn-as-he-goes mechanic like myself to do or should a shop do it to make sure everything is properly assembled?

 

[Sedition]

They fail permanantly so they can not be salvaged. It's only one bolt to change it and its position is keyed so I'd say that you would be able to change it blindfolded with one arm tied behind your back.

Once you have installed it, put your belt back on if it is not damaged, then insert your 3/8" drive ratchet into the square hole on in the tensioner to compress the spring to fit the belt on. Nice and simple.

 

[roboman]

Alright, cool, I'm glad this doesn't sound too bad. Is there a certain torque I need to tighten that bolt at? And when I use the 3/8 ratchet to tighten the tensioner in the proper position, is there a certain torque that needs to be at too, or is that what you're saying is keyed, and it will either be tightened or not tightened?

 

[gonenuke]

This is the front of the tensioner. You can see were the 3/8 ratchet fits to remove tension

The rear has two diffrent sized slots that fit the tensioner in the correct position.

Just torque bolt to 35 fp and your good to go.


Might want to replace the idler pulley while your at it. It torques to 35 FP also.