Serpentine Belt and Tensioner Replacement

[RBridenbaugh]

My serpentine (accessory) belt failed yesterday on my 3500. Luckily it was very close to home. Very easy to tell that it failed as power steering disappears, AC goes off, no alternator output and coolant temperature starts to climb. All this is before the “check gauges” message starts flashing on the instrument cluster.

Root cause was the failure of the tensioner, likely the bearing first then the idler pulley, as the plastic was melted around the bearing. See the images below of the failed Dayco tensioner (89094) compared to the replacement Gates tensioner (38285). Gates has a metal idler pulley vs. the Dayco plastic.

The plastic Dayco is about five fold less expensive compared to the Gates tensioner at Genos Garage. The price I paid for the Gates tensioner and Gates HD belt (K081264HD) at my local CarQuest was 2x that of Genos (the local Napa a little more than CQ), but I needed to get the truck running to leave for vacation tomorrow.

Not much room for a ratchet with a 13 mm socket to undo the tensioner, had to go in from the top. I removed the failed tensioner out the bottom with the fan shroud on (although I removed the two lower nuts holding the shroud so it can be collapsed). If I had more time I'd get a 13 mm ratcheting combination wrench, cut it in half and weld on a longer handle.

However, it is much easier to see what you are doing with it off when you are reinstalling it and tensioning the belt. I also removed the right front wheel and fender liner to make it easier to start the attaching bolt of the tensioner.

Routing the belt was just a matter of following the diagram below.

I elected to start by hanging it on the alternator and then left it off the AC pulley so there would be slack when I installed the tensioner. This made it easy to hold the ratchet on the tensioner pulley to make enough slack to easily slide the belt over the AC pulley from below. The service manual suggests leaving the water pump off and then using the tensioner to provide slack. My guess is they must have done all this from above, I didn't have much luck that way with the tools I had.

There is limited clearance between the tensioner pulley and the block (visible in the images above). If I only had to replace the belt, to make more room to sliding it rib side to the block behind the tensioner pulley and then over the tensioner pulley, I'd be tempted to loosen the tensioner attaching bolt to create a little more room and make the installation easier. Depending on the length of your ratchet, you can get to this attaching bolt from either the bottom or top.

Happy 4th of July

 

[Wayne M.]

Thanks for the good write up...

A GREEN drive belt? Hmmm. I do a pulley check once a year and I hold off the tensioner like in your second picture plus I clamp a vise grip on the sway bar to hold it, then I spin everything to see if anything sounds or feels like an old roller skate. Undoing the shroud gave you lots of room... .

 

[cerberusiam]

That is one way to do it. Removing the air box and doing it from the top is a lot less hassle and a lot easier to get to the bolt on the tensioner.

 

[Shadrach]

I changed the belt and tensioner on an 04 for a friend the other day and other than my 1/2" ratchet being to short for leverage it was easy from the bottom. I did have a friend hold the belt up from the top to keep it from falling in my way. His A/c compressor blew so I had to use a non A/C belt so the truck would be mobile and I will replace the comp and proper belt this weekend. I'm glad it was an 04 and not an 04. 5 as I had done my 03 already and new how to do it. I have the DSS steering stabilizer on mine so I can't use a long ratchet. It would be nicer if the factory diagram show the belt in their true position rather than spread out. David

 

[JR]

Now that you have one with a steel pulley you should be able to source a bearing for it through a NAPA or somewhere similar in the event it goes bad rather than replacing the entire unit.

 

[cerberusiam]

You don't have to replace the whole unit with the plastic pulley, the replacement pulleys are easily sourced. The tensioners rarely fail, almost always the bearing in pulley.

 

[BDaugherty]

i know it's not the most frugal way possible, but i prefer replacing the entire tensioner assembly. i think i've replaced as many with worn out bushings in the tensioner pivot as i have bearings in the pulley and i just consider it somewhat cheap insurance.

 

[JR]

You don't have to replace the whole unit with the plastic pulley, the replacement pulleys are easily sourced. The tensioners rarely fail, almost always the bearing in pulley.

What I meant was with the steel pully the bearing can be changed out for a few bucks rather than buying a new pully. I've not yet seen a plastic pully where the bearing can be pressed out. Not a big deal, some may feel better spending 20 bucks for a complete new pully rather than $3 or $4 for a bearing, but I'm a bit of a tightwad.

 

[cerberusiam]

What I meant was with the steel pully the bearing can be changed out for a few bucks rather than buying a new pully

Got it. Did not think those were replaceable in a cast pulley. Usually just get the Dayco pulley available about anywhere for $30.

 

[Prairie Dog]

I wouldn't replace a worn bearing. The spring rate is greatly diminished over the life of even one belt so a whole new tensioner is best in my book.

 

[RBridenbaugh]

That is one way to do it. Removing the air box and doing it from the top is a lot less hassle and a lot easier to get to the bolt on the tensioner.

Thanks for the hint on removing the airbox, a detail I thought would be in my service manual, but no ...

I'll try it from the top next time.