2004 4.6L V8 - Belt Slipping Laterally

[Onuma]

(( In case anyone asks, this truck has seen 165k+ miles, primarily around the New Jersey coastline where it is really wet & salty. Hence he surface corrosion on nearly everything and the quarter panel ))

Originally I replaced this idle pulley yesterday, which had been stuck long enough to develop a coating of rust around the exposed metal (bad winter, lots of salt & chems on the roadways). The belt is cracked up too, and due for replacement:

No problem, new idle pulley installed with barely a hitch. The belt was newly and properly installed (checked the diagram many times, as well as to make sure it was feeding correctly and lined up with all grooves in all pulleys).

Not a day goes by afterward, and the belt starts squealing when I'm at class. I check it out and notice that there is material rubbing off the engine-side of the belt. Further inspection reveals that the belt has actually moved over 1 full groove on all of the grooved pulleys, and an equal distance (roughly 1/8") on the small ones, causing it to rub against the beveled wheels. Even worse, as it rode over the tensioner, it was wearing against the (engine block?) and burning up.

Without much of an option, I figured out who had the parts I needed and drove it a couple of miles to the local Advance Auto. By this point, the belt had literally slipped past the edge of the tensioner, squeezed itself between that pulley and the block, and loosened itself from the other pulleys. I had to cut it loose to remove it

Fortunately, I happened to be in an auto parts store lot...unfortunately, the engine was so hot that I couldn't even work on it at the time, AND rain was inbound just a few minutes later.

So I sucked up my pride and called AAA Better to do this from home than out there.

My suspicion is that the belt tensioner assembly is bad. I have a replacement for it and a new belt to try, as well as the other 2 idle pulleys to install (might as well make them all new, right?). I'm hoping this does the trick, and it's not the harmonic balancer which is causing this problem all of a sudden.

I'm sure I can fix it, but I don't know how deep the rabbit hole goes. I need to get some pictures of where the belt was burning onto the other pulleys, but daylight was fading as I was towed home. This is first priority when I wake up in the morning.

Anyone else have a similar experience?

 

[Joe in NY]

I highly doubt its the idler pulley. In the second pic you can see the belt is NOT in the correct position on Tentioner pulley. I think you may have missed putting the belt on each pulley correctly or the tentioner is going bad and allowing the belt to get too lose...

 

[the_don]

Replace the tensioner assembly, pulley, arm, spring, everything. something went wrong and now its out of alignment. also might want to pull the idler pulley off to make sure the mating surface between the idler bearings and the little sub it sits on are clean.

 

[lincolnshibuya]

At that mileage definitely replace everything, tensioner with pulley and idlers. You'll be surprised that it sounds like new again.

 

[Onuma]

I highly doubt its the idler pulley. In the second pic you can see the belt is NOT in the correct position on Tentioner pulley. I think you may have missed putting the belt on each pulley correctly or the tentioner is going bad and allowing the belt to get too lose...

I'm pretty sure I had it in the right grooves, but I didn't check from underneath the truck when I first installed it, to be 100% sure. It could have been my mistake. You can bet I'll be doing that next time to avoid that possibility.

You noticed that the belt was too far inward/back on the tensioner pulley, but that's exactly what was happening even after I took the belt off and reset it. I had a buddy of mine take a look while I was investigating the squealing, so we had a set of eyes from the top and the bottom. Even when it was 100% lined up, as soon as the engine started it immediately slipped and began squealing/rubbing again -- it jumped grooves the moment it had enough torque applied.

 

[Joe in NY]

That means your tentioner spring is weak and needs to be replaced.

 

[Onuma]

Thanks Joe! It was the tensioner -- and it was BAD. You'll see why.

So I got it all done and wrapped up a few minutes ago. Running nicely now. Here are some photos...

Obviously, something is wrong here. The pulley shouldn't be up against the engine, flush:

Here's the tensioner assembly, where the pulley sheared off after the bearing failed:

Closeup of the friction area, which rubbed about 1/4 of the way to the center of the axis:

This is the engine block, where the pulley wore a groove after it had detached from the arm:


You can see the trail of rubber left by the belt which was burning up, on these few pulleys (also, is that the "weep hole" for the water pump on the lower right corner? Does that mean it's bad, or just getting gunked up from other things, corrosion, etc?):


Other pulleys replaced, for good measure -- better to do it once and do it right than to revisit this crap again:
[
New belt in place, looks to be tracking well:



Also, here's a video (just mute it, lots of noise from the fan) of everything running. I tried to get every pulley from both angles...but I think this should do.


It could have been a lot worse, admittedly. About $200 in parts & tools to fix this up, and no charge for the tow since I'm already a AAA Plus member.

 

[Bobmbx]

You didn't notice any noise before this happened? Maybe started out like chirping or jingle bells, then graduated to horror house shrieking?

 

[Onuma]

There was no chirping, no jingling, no rattling. Surprisingly enough, I drove to school in the morning (8 miles or so) without a sound. When I went to head out in between my final exams (3 hour gap ) to go to the store, I heard it squealing like crazy.

I'm pretty sure the act of changing the belt the day prior -- when I first noticed the stuck idler pulley above the tensioner arm -- was what finished off the bearing in the tensioner arm. It was holding together before that, but was basically on borrowed time. Even with a brand new belt, fewer than ~15-20 miles had burned it up when that bearing blew out.

I was troubleshooting the noise as it occurred. Once I realized the extent of the problem, I just went ahead and chucked all of the pulleys and the arm assembly, replaced them with new parts. The only thing that bugs me is one of the replacement pulleys, the grooved idler/tensioner pulley on the driver's side, is actually made of plastic -- Dayco "No Slack" brand. It has a 1 year warranty, but I'd like to find a metal replacement. This engine tends to run hot, which explains some of the corrosion everywhere...I don't know if that plastic will hold up to the temperatures.

 

[the_don]

Something went VERY wrong!! glad to see you got it fixed without too much collateral damage.