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How to Replace Serpentine Belt Idler Pulley 01-05 BMW 325Xi

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  1. step : Removing the Radiator Fan and Shroud (0:25)
    • Disconnect the negative battery cable by loosening the 10mm nut
    • Remove the air collector push pin retainers
    • Remove the air collector
    • Disconnect the two electrical connectors on the passenger side of the fan shroud
    • Remove the T25 screw from the passenger side corner of the fan shroud
    • Remove the push pin retainer from the driver side corner of the fan shroud
    • Loosen the radiator fan clutch using a fan clutch tool
    • The fan clutch is reverse threaded
    • Remove the fan and fan shroud
  2. step : Removing the Serpentine Belt Idler Pulley (4:25)
    • Turn the AC belt tensioner clockwise with a 16 mm socket
    • Remove the AC belt
    • Release the AC belt tensioner
    • Loosen the serpentine belt tensioner with a 16 mm socket
    • Insert a pin through the tensioner hold holes
    • Remove the serpentine belt
    • Remove the 16 mm idler pulley bolt to remove the idler pulley
  3. step : Installing the Serpentine Belt Idler Pulley (7:15)
    • Install the idler pulley using the alignment tab as a guide
    • Install the 16 mm idler pulley bolt
    • Torque the 16 mm idler pulley bolt to 30 ft-lb
    • Replace the idler pulley cover if equipped
    • Slide the serpentine belt over the crank pulley, to the right around the power steering pulley, loop the belt around the tensioner pulley, and back over to the water pump pulley, bring the belt over the alternator pulley, then under the idler pulley
    • Loosen the tensioner with a 16 mm socket to get the belt under the idler pulley, then remove the pin and then release the tensioner
    • Loosen the AC tensioner with a 16 mm socket
    • Install the AC belt around the crank pulley and the AC pulley, and over the tensioner pulley
    • Release the AC tensioner
  4. step : Installing the Radiator Fan and Shroud (10:09)
    • Lower the radiator fan and fan shroud together
    • Tighten the fan clutch onto the water pump pulley by turning it clockwise
    • Torque the fan clutch nut to 22-29 ft-lb if able
    • Install the fan shroud push pin retainer on the driver side
    • Install the fan shroud T25 screw on the passenger side
    • Reconnect the two electrical connectors on the passenger side of the fan shroud
    • Insert the air collector into the air filter box
    • Secure the air collector with the push pin retainers
    • Reconnect the negative battery cable and tighten the 10 mm nut

What's up guys? I'm Andy from 1A Auto. In this video I'm going to show you how to replace the serpentine belt idler pulley on this 2001 BMW 325Xi. If you need this part or other parts for your vehicle, click the link in the description and head over to

With the trunk open, over on the right side or the passenger side, there should be a cover that goes right here. This vehicle doesn't have one, but you're going to want to remove that cover. Battery is located right here. First thing I'm going to do is take a 10 millimeter socket and a ratchet. Loosen up this nut for the negative terminal. And that's loose. Slide off the cable, slide it out of the way. I'm going to take these push pins out right here. I'm just going to use some side cutters. Get this center pin, pull that up, and then slide it out.

Be careful not to cut that. Get those up. Just grab this piece, slide it out. We're going to disconnect this connector right here. Just push down on that, slide that out. There's another connector right here. I'm going to slide the wiring out first, just like that. Then the connector will come out. Then just slide that to the side like that. I'm going to take a T25 and a ratchet. Take this screw out right here. I'm just going to use this trim tool from Take this push clip out, get in there. Pull that out. All right, now that is loose.

But what we need to do is, we need to take the fan off because the fan has to come out with the shroud as one. What we need to do to take the fan off is, we need to disconnect the fan clutch from the engine side. This is attached to one of the pulleys right there. So sometimes these are somewhat difficult to get off, so what we're going to do is use this tool. We actually sell this at with many different sizes. This happens to be the 32 millimeter. That's going to slide on there. And then we slide this on and with a pneumatic air hammer we're going to give it a couple of bumps, and it's going to loosen up that nut and we should be able to get it off. All right, so now I'm going to take the tool. Now this fan clutch happens to be on their reverse thread, so it's going to seem like you're tightening, but you're actually loosening it. So we'll go like that. Put our air hammer on there. Make sure you wear hearing protection and eye protection.

All right, so that's loose. Took a little bit of effort but I got it. Now you can slide the tool off. We'll just move it a little bit. Here we go. You should be able to just spin it off like that. I might need the tool once in awhile or you could use a wrench that fits 32 millimeter wrench. All right, now I'm just going to keep loosening this up. Be careful, you don't want the fan to fall. You don't want it to smash into the radiator. Especially if you're going to re-use the radiator. If you're replacing it, it's not a big deal. So I get closer to the end, I'll just move the fan and just grabbed the blade.

There we go. Now I can slide this right up. Just like that. For this job that we're doing, you don't necessarily have to have the coolant drained or the coolant hoses off or the air box out, but it's easier to see with the camera, so we're going to leave that stuff off. Just keep in mind you don't have to do all that to get to this position. I'm going to take a 16 millimeter socket and a ratchet, and I want it on tightening. I'm going to go down here and get on the tensioner right there. You could use a serpentine belt tool as well, and then I can loosen up the belt just like that.

That's how it looks from underneath. With that loosened up, I can grab the belt and slide it off the crank, and then slide it off the AC compressor. I'm going to take this serpentine belt off. What I'm going to need is a hex key. This happens to be a five millimeter hex key and I'm going to use this 16 millimeter socket and a ratchet. Put the ratchet on tighten and then right here on the tension here is a little area you can put the socket, and then you're going to tighten it like you're tightening a bolt. That's going to loosen up the tension on the belt. We can take this hex key and slide it in that position. That's going to lock the tensioner. Let that go. Then we can grab the belt, slide it off the idler, slide it off the alternator right there. Can pull our socket away, pull it off the water pump, off the tensioner, off the crank and off the power steering pump.

Just like that. I'm going to take a 16 millimeter socket and a ratchet, and we'll take this bolt out right here. Loosen it up. Loosen that up, slide that bolt out. Here's the old part. Here's the new part from The pulleys are the same, same size, same design, has the same cam right there, same index. Flip it over. The other side's the same. This one has a little cover on it. Take a little pick, take this cover off before you install it. The bolt is going to go through that hole. Get yours at and you'd be ready to rock and roll.

The new idler pulley has a little cover right here. Just take a pocket screwdriver, slap that cover off, take the bolt, slide it through here. There is a little nub right on the end of the idler. It's going to line up with the slot in the alternator. Get that started. I'll just take a 16 millimeter socket and a electric ratchet. You can use a regular ratchet if you don't have an electric one. And again, tighten this down to 30 foot pounds. And that's good. Now we can you take this cover, put the cover back on. Just like that. We're going to take the belt, slide it over the crank pulley down below, and then with this other side, go over the power steering pump pulley over there. Then it's going to come around on the tensioner side on the tensioner pulley. Just like that. Then we'll go over the water pump. We'll go over the alternator over here. Just like this.

And then we want to go below the idler pulley. Now we're going to have to put the socket and the ratchet on the tensioner and relieve some of the tension to get that all the way on. So I'm going to take the 16 millimeter socket and the ratchet, and then you need to have this on tighten. So we're going to loosen the tension on this and slide the belt underneath there. Make sure that's all lined up and when that's all lined up. Then I can pull this pin out of the tensioner and let it go. Double check your belt. Go round all the pulleys, make sure it didn't pop off that new power steering pump or the alternator. It looks good. It's going to be a little bit easier to install the belt from underneath. So we're going to do that. We'll just take the belt, slide it over the AC compressor and slide it over the pulley for the tensioner and then over the crank pulley.

Make sure these are all lined up and that's good. Just like that. Make sure those are good. Take a 16 millimeter socket and a ratchet, slide it into the tensioner, relieve the pressure, and then slide this pin out. Or if you use the hex key, pull that hex key up. Double check that. Looks like everything's lined up and we're good to go. So these have to go on together. Just slide this in position. Once you get this close, I'm going to start to tighten up the fan. Now these fan blades are the fan clutch is reverse thread, so it's almost like you're going to be loosening it.

It's really no easy way to do this. Just do it carefully. Once you get it started, it's a little bit easier. Make sure the fan shroud is in properly. That's good. All right. If you have the ability to torque this nut for the fan, you're going to torque that between 22 and 29 foot pounds. I don't really have that ability, so I'm just going to put this tool on there and just give it a little tap. That should be good. Right here there's a push pin that's going to go back in here, Slide that in position and lock it down. And on this side we're going to put this screw right here and I'm going to use a T25 and a electric ratchet. Tighten this down. Just snug. I'll put ... Position this wiring harness right here and we'll plug the connector in right here.

Lock that into place. Take this piece, slide this into the air box. Just like that, and there's retainers right here. Take those push pins, lock them down. Then we can take the negative side, connect the negative side, take the same 10 millimeter socket and ratchet, tighten it up. That's good. At this point, if you had that cover, you're going to want to put the cover back where it goes.

Thanks for watching. If you want the parts to do it yourself, check out, the place for DIY auto repair.

Tools needed for replacement:

    General Tools

  • Hammer
  • Pick

  • Hex Wrenches

  • 5mm Hex Wrench

  • Pliers, Cutters & misc Wrenches

  • Side Cutters

  • Ratchets & Related

  • Socket Extensions
  • Torque Wrench
  • Ratchet

  • Screwdrivers & Related

  • Flat Blade Screwdriver

  • Sockets - Metric

  • 16mm Socket
  • 10mm Socket

  • Specialty Tools

  • Trim Tool Set
  • Fan Clutch Wrench

  • Star Drivers & Sockets

  • T25 Socket
  • T20 Socket

2001 - 2005  BMW  325Ci
2000 - 2000  BMW  323Ci
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1991 - 1995  BMW  325i
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2001 - 2002  BMW  325Ci
2003 - 2003  BMW  325Ci
2001 - 2002  BMW  325i
2003 - 2003  BMW  325i
2001 - 2002  BMW  325Xi
2003 - 2003  BMW  325Xi
1999 - 2000  BMW  328i
2001 - 2002  BMW  330Ci
2003 - 2003  BMW  330Ci
2001 - 2002  BMW  330i
2003 - 2003  BMW  330i
2001 - 2002  BMW  330Xi
2003 - 2003  BMW  330Xi
2001 - 2003  BMW  525i
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2003 - 2003  BMW  X5
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2003 - 2003  BMW  Z4
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1995 - 1995  BMW  318ti
1992 - 1995  BMW  318iS
2001 - 2006  BMW  325Ci
1999 - 2000  BMW  323i
1998 - 1999  BMW  323iS
1994 - 1998  BMW  318i
1994 - 1997  BMW  318iS
1992 - 1995  BMW  325i
1994 - 1995  BMW  325is
2001 - 2005  BMW  330Ci
2001 - 2002  BMW  525i
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