How to Replace Serpentine Belt Tensioner with Pulley 1996-2004 GMC Sonoma

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In this video, we're going to show you how to replace the serpentine belt on this 2003 GMC Sonoma. It has the 4.3-liter. It's a pretty easy operation, you need a 3/8 drive ratchet handle as well as a 13mm socket.

Look at the top of the alternator. Right down here is your tensioner. I've got a 3/8 drive ratchet handle. There is a 3/8 square hole in the tensioner. Take your handle, push down. That takes the tension off the belt, and put the belt off. Slowly let your tensioner back, remove your handle. To proceed with removing the tensioner and reinstalling it, you don't have to take the belt off all the way, but I am going to show you how to take it off, and then also how to put it back on, just in case it comes off a couple pulleys or something. This just gives you some guidance on getting it back together if you need it.

Okay, here's our belt routing diagram. Always want to make sure you have this before you take the belt off, and then I can remove the belt. So, your tensioner right here, it's got a 13mm bolt right on the front, so I'm putting a ratchet and socket on it, and it's pretty tight to loosen. I'll speed it up here as I remove that bolt, and, as you can see, after you get it loose with the wrench, you can switch over to your hand and thread it out by hand. The tensioner will come right out.

Get your tensioner from 1AAuto, bolt goes through there. This pin on the tensioner. If you look down where it mounts, you can see the hole and then this smaller hole where that pin lines up into. Just drop the bolt through, put the bolt in. Make sure that tab goes into the indentation and start the bolt in. Speed it up again as I thread the bolt in mostly by hand, and then I'll switch over to my ratchet and socket to tighten it up. You probably want to tighten this to belt 25 to 30 foot-pounds.

Now, back to our belt routing diagram. What I'm going to do is take a loop and put it down around the crankshaft first, then come up and down around our power steering, up to our AC, and then over. What I'll do is I'll leave it off this idler pulley here so it'll just go right above that, and then we'll pull the tensioner over, and put it down onto that idler pulley. Then I take a loop and I'll put it right down through here, and then just kind of take my hand, put it up onto the crankshaft pulley, and then it's coming around the water pump here, and now I'm reaching down here and putting a loop down, and around the power steering pump which is down here on the right side as you're looking at the engine. Pretty tough to get your arm down in there. Then it comes up around to the AC compressor, and across the alternator. I think it came off my crankshaft, so I'm going to put my arm down in there and make sure it's down and around the crankshaft.

So, basically now, I have it routed around my tensioner there. It's not around this idler pulley yet. It's on my AC pulley, it's down there on my power steering pulley, and also down and around the crankshaft pulley. A little hard to see way down there. So, I take my 3/8 ratchet handle, put it into my tensioner again, push my tensioner down, and then take this and put it right down. I'll have to pull it a little bit because it's going to need to tighten it up around all the pulleys.

As I was trying to do this, I realized that it actually had come off the crankshaft pulley a little bit, so I'm reaching down in there, and I'm making sure it's on that crankshaft pulley correctly. So now I push that under there, and let it off. Okay, it's now under the idler pulley, around my tensioner, down and around my power steering pulley, up and around. The only thing I can't really show you is the crankshaft. You can see it down there, and maybe a little bit right down there. It's all in there correctly, though.

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