How to Replace ALH Serpentine Belt Tensioner and Idler Pulley (with photos)

alkmisc

Veteran Member
Joined
Apr 3, 2008
Location
VT
TDI
2000 Jetta (6 speed)
There are a bunch of threads talking about replacing the serpentine belt tensioner and idler pulley but mostly without pictures so I thought I'd add some.

There was a noticeable rough sound from the passenger side of the engine compartment after my car met a large pothole. Taking off the timing belt and spinning the various pulleys, the idler pulley had a noticeable grittiness that didn't belong there. I though I'd replace the tensioner too at 127K miles while I was there.

The tools you will need:
16 mm box wrench (notice two wrenches hooked together)
13 mm socket (may need regular and deep)
extension
6 mm hex bit (the shorter the better)
torque wrench
ratchet
flathead screwdriver
pliers
tools for removing skid plate/belly pan and side skirt



**** Torque value to remember - 18 ft-lbs ****

Here is the new tensioner and idler pulley. It even comes with a new hat for the pulley!



1. Put the car on ramps, chock wheels, remove the skid plate/belly pan and passenger side side skirt. Open the hood (do I need to say this?).

2. Here is the tensioner from above and where the serpentine belt runs over the PS pulley.



3. The tour from below - take note of the routing of the belt:
(1) crankshaft pulley
(2) AC pulley - may want to check tightness of 14 mm nut while there
(3) idler pulley
(4) power steering pump pulley
(5) alternator pulley
(6) tensioner and pulley



4. Remove the serpentine belt by placing the 16 mm box wrench onto the "nut" on the tensioner and pushing back towards the firewall (the direction of the arrow) to relieve the tension and slip the belt off the pulleys. I used a second wrench on the end of the first for extra leverage and to reduce the chance of pinching myself. (If you're only replacing the serpentine belt, just reverse the steps from here and you're done.)



5. Pop the "hat" off the idler pulley with a screwdriver and loosen the bolt with a 6 mm hex wrench. If you use a socketed bit like I did, use the shortest one you have since clearance is tight. I had to loosen with the bit, remove the bit, then take the screw out by hand, then remove the pulley.

6. Remove the 3x 13 mm bolts holding the tensioner (arrows in photo). It may help to remove the upper hose leading to the EGR to give yourself some wiggle room.



7. Here are the 3 bolts for the tensioner and the bolt for the idler pulley. Note that one of the tensioner bolts is longer. That goes through the hole in the thicker part of the casting that you will see.



8. Here are the new and old tensioners. The new one is folded like it is probably to reduce shipping size. You will need to remove the pin (yellow circle) at some point so that it will actually work. I recommend doing this before trying to put it in. Put your box wrench on the nut and set that end against the ground, push down a little, and pull the pin out with pliers - easier done than described.



9. Reinstall in reverse order. No pictures here because it looks just like before except with newer shiny parts. Torque the tensioner bolts to 18 ft-lbs. The idler pulley bolt is also 18 ft-lbs but I had trouble getting a torque wrench in there so tightened it to what felt tight enough. I'll recheck the tightness later down to road to make sure it hasn't loosened. Remember to put the new hat back over the idler pulley to keep things clean, to. When putting the belt back on, you'll notice the new tensioner will be stiffer than the old one.

10. Reinstall side skirt and skid plate/belly pan.

The postmortem showed that the tensioner pulley was freewheeling much more than the new one. The old idler pulley was definitely due for replacement, too. It sounded gritty spinning in hand and had noticeable side-to-side play and it rattled loudly if you shook it gently.
 

alkmisc

Veteran Member
Joined
Apr 3, 2008
Location
VT
TDI
2000 Jetta (6 speed)
VWMod said:
And i cant seem to get the pin out :-x
Put the 16 mm box wrench on the nut of the tensioner so that it's parallel to and on the same side as the black piston thing (the whole thing will look like a "U"). Put the whole thing so that the box wrench and pulley (one side of the U) are on the ground (basically stand the U on it's side) and push down on the piston (the other side of the U) towards the ground while pulling the pin out at the same time. It's hard to describe but once you can figure it out it makes sense. This is the one picture I should have taken but forgot.
 

nh nam vet

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Oct 27, 2008
Location
Raymond, NH
TDI
2- 97 Passats , 02 Jetta
Last week I swapped out the Bosch 120 amp alternator in our 2002 ALH Jetta. The serpentine belt tensioner is indeed secured with three 13 mm hex head bolts, but on our engine they are all different lengths! The correct installation combination is......top to bottom: short, medium and long. I hope this saves somebody a little time.
 

spoilsport

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Oct 3, 1999
Location
Houston TX
TDI
2000 Golf GLS Silver (Sold). 2005 Jetta TDI Wagon Tiptronic (daughter's)
thanks!

alkmisc said:
Put the 16 mm box wrench on the nut of the tensioner so that it's parallel to and on the same side as the black piston thing (the whole thing will look like a "U"). Put the whole thing so that the box wrench and pulley (one side of the U) are on the ground (basically stand the U on it's side) and push down on the piston (the other side of the U) towards the ground while pulling the pin out at the same time. It's hard to describe but once you can figure it out it makes sense. This is the one picture I should have taken but forgot.
Thanks for the nice tip. This worked like a charm! :)
 

reyemtm

Member
Joined
Sep 22, 2010
Location
Wooster Ohio
TDI
99 Jetta MKIV
Incorrect...to change the belt you need to REMOVE the idler pulley. Also, there are at least three different belts available for the Jetta ALH so make sure to get the right one there is a ten mm difference in the belt sizes. And they are a tiiiight fit. And you need to seat the belt on theadd and alt and then reinstall the pulley and route the rest of the belt.
 

alkmisc

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Joined
Apr 3, 2008
Location
VT
TDI
2000 Jetta (6 speed)
I was able to remove and install the belt with all pulleys in place. It is a small space to work. You need to take the tension off the tensioner before putting on or taking off the belt and you need to remove the belt to change the idler (unless someone else is taking the tension off the tensioner for you). I've only seen one belt being sold for the ALH by the US online sellers.
 

pcjr

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Oct 13, 2002
Location
Felton, DE
TDI
2002, Jetta, Baltic, 2010 Jetta Sedan
Does anyone know the size of the bolt that holds the round bar to the assembly. The bolt in missing on my 2002 TDI. :(
 

Genesis

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Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
There is no need to remove the idler pulley to get the belt out (or in) on an ALH.

Beware that idler pulley bolt -- overtightening it will lead to it breaking down the road and if it breaks you lose the serpentine drive and then have fun trying to extract the stub from the bracket. Not good. A stealer overtightened mine a long time ago in a galaxy far far away and fortunately I was only 30 minutes from home and beat the clock (battery charge state) to where my wrenches were. I am still running a conveniently-sourced grade 8.8 replacement there 100,000 miles later, although the idler has since been replaced. That idler should probably be replaced when the timing belt is done as a failure of the bearing will take out your serpentine drive and it's not very expensive. The tensioner shock fails much more frequently than the tensioner itself wears out and the shock can be replaced separately (for significantly less money than the entire tensioner.)

It is next to impossible to get a torque wrench on all three tensioner bolts due to clearance issues. "Decently tight" using a box-end wrench (and NO extension bars for more leverage!) is pretty close to 18ft/lbs and those bolts are larger than the idler bolt and therefore less-likely to strip.

Note that if you strip anything on that bracket (it holds basically everything in accessories on the engine) you're in quite a bit of trouble, so do use reasonable care -- don't be an ape.
 

GIDDY_UP_GO

Veteran Member
Joined
Mar 11, 2007
Location
Indiana
TDI
10 Jetta 13 Beetle Convertible 15 GSW
To the OP, thanks for this write up! I was really dreading doing my ALH serpentine belt replacement, but it really wasnt that bad at all. I actually went to sears and bought this:



This flat bar with the socket attached to the end made a world of difference when relieving the tension on the tensioner. I even went one step further and used a zip tie to hold the flat bar back against the firewall while I removed and replaced the belt.

I also removed my top and lower intercooler pipes for easier access and more room.

And you do not have to remove the idler pulley at all to remove and replace the belt.

Took less than 30 min to do the procedure. I would also reccommend using ramps or a jack stand to get under the car for easy access.

By the way, does anyone know how long these serpentine belts last? Mileage wise?
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
I can get the serp belt off on these cars in about 15 seconds using nothing more than a box-end wrench as shown. Push it back and pull the belt off the AC compressor pulley -- done. To re-thread do everything EXCEPT that pulley, then lever back and slip it over. Done.
 

2000golftdigls

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Jul 9, 2011
Location
Rockport, MA
TDI
2000 Golf TDI GLS
The tensioner shock fails much more frequently than the tensioner itself wears out and the shock can be replaced separately (for significantly less money than the entire tensioner.)
Does anyone know where I can get the tensioner shock?
 

rudall42

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Apr 17, 2009
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carbondale, colorado
TDI
Jetta 03, NB 05
Genesis

please remind me: which one is the AC compressor pulley?

sounds like a neat trick, and an easier way to mount dismount that belt.
 

2000golftdigls

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Jul 9, 2011
Location
Rockport, MA
TDI
2000 Golf TDI GLS
Thanks Genesis,
My tensioner appears to operate normally, but the shock is leaking. The description mentions that the shock can be installed with the tensioner in place. I imagine you'd have to take the pressure off the tensioner before unbolting the old shock or installing the new one.:D
 

Chopper269

Member
Joined
Feb 23, 2010
Location
NJ
TDI
2001 Golf, 5 Speed. 300k and counting
Just want to thank alkmisc for posting this how to. Very easy job. Took my time and everything went smooth. Took about 45 mins to do. Amazed once again of the wealth of knowledge available on here.
 

fossill

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Mar 22, 2008
Location
Canada
TDI
Golf
Note that if you strip anything on that bracket (it holds basically everything in accessories on the engine) you're in quite a bit of trouble, so do use reasonable care -- don't be an ape.
If you do strip one, tap it with a 3/8 course tap and resize the hole in the tensioner and you'll be good to go. Theres a write up in one of the posts on here for that. Good to know if you ever get in a bind.
 

brandonkraemer

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Dec 28, 2013
Location
Cincinnati, Ohio
TDI
2003 TDI 1.9L 5spd ALH VE mkIV Jetta Wagon
This is very helpful... and the step by step directions are well explained, as was the pin removal from the new tensioner description.

One thing I ran across... while I could use a 16mm box wrench on the stock tensioner to loosen the belt, with the replacement tensioner on, 16mm was too loose and was giving way so I used a 5/8" box wrench and it held tight.

Also, I ran into stripped threads on the longest mounting bolt for the tensioner... it was over torqued when I removed the stock one, possibly due to the bad vibrations it was getting from the damaged tensioner. Discovered this when I went to re-thread that bolt back on the replacement tensioner.

This is just speculation, but when the alternator clutch pulley blew about 60k ago the mechanic didn't replace the tensioner or idle pulley at that time and I think that caused some issues.

I did of course check the operation of the clutch before wrapping this job up again.
 
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coachgeo

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Mar 5, 2006
Location
Dayton OH area
TDI
99 Blue Bug.. new top end
So this looks to be a "must get underneath car" only project? Shiat... dont have that option. Was going by a BEW belt replacement thread which can be done from above before realizing mine was ALH and they are too different to have any crossing in the procedure.

or am I missing something? There is a square hole in tensioner case that appears would make a good leverage point to tip the tensioner up. Appears a 1/2 socket drive wrench would to fit into but noooooo.. there is a rib inside of it so wrench stub wont goin int to it.
 
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brandonkraemer

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Dec 28, 2013
Location
Cincinnati, Ohio
TDI
2003 TDI 1.9L 5spd ALH VE mkIV Jetta Wagon
Yes, you need to work from above and below on this one. Mostly from below. I purchased some Rhino Ramps (hard plastic ramps) from AutoZone specifically for this project. Weren't too expensive and I've used them now on a number of other tasks.
 

coachgeo

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Mar 5, 2006
Location
Dayton OH area
TDI
99 Blue Bug.. new top end
Yes, you need to work from above and below on this one. Mostly from below. I purchased some Rhino Ramps (hard plastic ramps) from AutoZone specifically for this project. Weren't too expensive and I've used them now on a number of other tasks.
Yeah, my last pair got stolen. Got another pair along with a tons of other stuff shipped here recent from my old place. Taking me forever to dig thru the unit it was shipped in. About size of a 8x20 cargo container packed full.

I'll try again tomorrow after jacking it up and throwing jack stands under it. I found those.
 
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