I have a 2008 GMC Sierra 1500 with an AC belt that is cracking and needs to be replaced. The belts and tensioners are original. Should I replace the serpentine and AC belts, both tensioners, and the idler pulley all at the same time?
Belt replacement best practice
- Thread starter shurguywutt
- Start date
all the belts should be replaced, but you don't necessarily have to replace the tensioner or pulleys unless you think something is wrong with them 
I have needed to replace tensioners and pulleys before, but they were much older cars and didn't even have spring-loaded tensioners.
With the belt off, spin the pulleys by hand. If they're smooth, there is nothing to worry about
The good news is that OE belts are still available for your 2008 Sierra at a fair price.
I have needed to replace tensioners and pulleys before, but they were much older cars and didn't even have spring-loaded tensioners.
With the belt off, spin the pulleys by hand. If they're smooth, there is nothing to worry about
The good news is that OE belts are still available for your 2008 Sierra at a fair price.
I rarely trust aftermarket tensioners as much as used OEM, unless they seem noticeably loose or "sticky"
Spin idlers by hand and rock them. If they sound like skateboard wheels or feel crunchy or have play, replace. I prefer to press new bearings into steel pulleys where applicable
Spin idlers by hand and rock them. If they sound like skateboard wheels or feel crunchy or have play, replace. I prefer to press new bearings into steel pulleys where applicable
The job is so simple I'd only do what's needed, but inspect everything.
If your tensioner is on its way out it may feel crunchy going through the range of motion, and then not tension properly on a new belt.
But once you get the muscle memory for your truck, you can change belts in a minute or two. So I'd throw the new belts on and see how they do.
Don't buy Dayco Drive-Rite, they're garbage and squeal.
If your tensioner is on its way out it may feel crunchy going through the range of motion, and then not tension properly on a new belt.
But once you get the muscle memory for your truck, you can change belts in a minute or two. So I'd throw the new belts on and see how they do.
Don't buy Dayco Drive-Rite, they're garbage and squeal.
How about Bando? I have used them before on my Honda's and they seemed good quality and worked fine.
Dayton says life of a serpentine belt is 70,000 miles. 3 cracks per inch is ok, 4 cracks per inch..replace. I showed a belt I thought was shot to a Dayco rep, he said it’s still serviceable. Gusss my OCD won’t allow that.
The idler pulley on my 400K Xterra is original. Still going after all these years. I have 3 new spares - different post. Might change it soon anyway.
The tensioner and pulley have been replaced a few times. Not sure why it wears out and the idler does not.
Not sure what to tell you, but so far I wait till something starts squeaking. The belt however I change on intervals - they seem to fail much more quickly with less warning
The tensioner and pulley have been replaced a few times. Not sure why it wears out and the idler does not.
Not sure what to tell you, but so far I wait till something starts squeaking. The belt however I change on intervals - they seem to fail much more quickly with less warning
Bando is good, but since you can get GM OE at a fair price, it's worth going OEM
I do do the tensioners and idlers. When I did them on my truck, I ordered ACDelco which ended up being reboxed Gates.
On my previous 04 avalanche, I popped the seal on the idler pulley, cleaned and re greased with valvoline red, and re installed it. It worked perfect, but ended up putting in a new pulley months later because it was only $14. If you are keeping the truck for another 5 years or so, replace the idler pulley, if the tensioner is still ok, I’d leave it.
Do the pulley bearings in my 21 year old Ford Ranger (single accessory belt) with <62k age with time too?
If a tensioner includes a metal spring, it can rust, and crack (break), yes?
If a tensioner includes a metal spring, it can rust, and crack (break), yes?
Ebay and Amazon seem to be full of fakes. But any major brand oughta be fine. I usually try for SKF, Timken, Koyo, FAG or Nachi
Most recently I bought from RA. All caveats on combining shipping, etc apply.
It doesn't necessarily save you a lot of $ but the advantage is that you can resurrect most any steel idler without ordering a specific pulley if you just have a couple 6203 and 6303s on the shelf. Toyota uses a 5xxx something I can't recall but I keep a couple of those, too
Most any parts house idler like Gates has a Chinese bearing, so if you can install euro, US or JP COO you're probably ahead of the game
I would change both belts and if the tension is good on those old belts, I would leave the tensioners alone. They are likely of better quality than replacements.
I'd like to chime in and say when you replace the belts on that car, use Original Equipment if you can possibly find it.
I made the mistake of using a Dayco serpentine belt on my Buick and no matter how many I took back to the store, they started squealing again until I got an AC Delco.
A few thoughts: serpentine belts often look perfect immediately before failure. While they can last a long time, there is minimal economic benefit to not replacing them early, as they are reasonable. The tensioners and related pieces are wear items. Oem, Dayco, Bando and other recognized names are all excellent. The his is a good place to stay away from unbranded or unknown Chinese stuff.
Bando is excellent. It has electrolytes.
The spring in tensioners often gets work hardened and overtighens the belt, especially with high hours. Had a customer that kept replacing water pumps with blown out bearings due to an old tensioner.
Here's simple test to determine if a tensioner/idler pully needs to be replaced: With the belt off, spin the pulley. If it continues to spin for more than 1/2 a second the pulley needs to be replaced. Why? The lubricant in a good pulley will slow the pulley very quickly. If it continues to spin more than 1/2 of a second the lubricant is gone. Replace all the pulleys at 1 time.
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