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

SmoothVW

Active member
Joined
Jan 30, 2014
Location
Ontario
TDI
2001 Jetta TDI, 99 Beetle TDI
Belt that fits

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.
Yep, the one belt available for the ALH is priced high. I used a spare belt from my 1995 BMW 318i. The belt fits like a glove, it has been on my TDI for the last 2 years. I just bought another BMW belt for a friend's beetle. It was just 7 bucks. When ordering, make sure to order the one that moves the water pump, alternator and radiator fan on the 318's M40 engine.
 

UncleSpence

Well-known member
Joined
Aug 28, 2015
Location
Bryan, TX
TDI
2003 Jetta
Roughly how much time should I allow?
I was able to replace both front rotors, serpentine tensioner, alternator pulley, and idler pulley in a little under 2 hours. If I had just done the tensioner it probably would have taken like 35 minutes with taking off the tire and everything. That and the idler pulley were probably the easiest thing in my opinion. The pin can also very easily be removed in the new tensioner by putting it in a vise and then just putting the 16mm box wrench on it and cranking on it. It took like 30 seconds.
 

Richy_T

Veteran Member
Joined
Apr 18, 2007
Location
Dickson, TN
TDI
2000 Jetta
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.
I also found this. Odd as it seemed to come out normally and I don't recall it being an issue when I had the tensioner off for changing the timing belt. I guess I'll just work with what's there until it comes time to do the timing belt again and all that stuff becomes accessible.

I'm even only doing the tensioner because I had the idler self-destruct and when I replaced it and the belt, it became very noisy. It has helped but there's still some noise. I'm thinking the idler I got from Autozone isn't very good so I think I'm going to get ahold of the proper one.
 

Richy_T

Veteran Member
Joined
Apr 18, 2007
Location
Dickson, TN
TDI
2000 Jetta
I was able to replace both front rotors, serpentine tensioner, alternator pulley, and idler pulley in a little under 2 hours. If I had just done the tensioner it probably would have taken like 35 minutes with taking off the tire and everything. That and the idler pulley were probably the easiest thing in my opinion. The pin can also very easily be removed in the new tensioner by putting it in a vise and then just putting the 16mm box wrench on it and cranking on it. It took like 30 seconds.
I recommend removing the pin before putting the tensioner on. I didn't because it seemed like it would make it easier but the tool I used (the one someone posted a picture of earlier. Decent tool BTW) got trapped when I released the tension and was a PITA to break loose. Might be possible to do it without issue though.
 

Mike Aucott

Member
Joined
Oct 31, 2011
Location
New Jersey
TDI
2003 Golf TDI
replace belt tensioner VW TDI

I just replaced the belt tensioner on my 2003 VW TDI. I didn't replace the serpentine belt itself as it was in fine shape. Replacing the tensioner went fairly smoothly. Here's what seems an easy way to do it. I'm assuming you start with a new tensioner assembly which comes pinned in the folded position, i.e., with the wheel that actually puts the tension on the belt up and away from the extended position it normally would be in.

If you still have a belly pan (mine is long gone), remove that. Then, with a 16 mm (pretty darn close to 5/8") wrench, accessing from below (you can do this from above but it's easier from below), turn the 16 mm nut cast into the tensioner housing clockwise and thereby crank the tensioner on the car into the closed position, like the new assembly. Then have a helper (from above) slip a nail or similar pin into the two holes that line up like the new, pinned, tensioner. (Or, you can crank the tensioner from above and slip the pin in yourself.) Then the tension will be off the belt and it is a simple matter to undo the three 13 mm bolts that hold the tensioner in place and then wriggle it out. It comes out from above fine. Reverse these steps to install the new tensioner. Make sure the belt is still lined up with its grooves in the proper slots on the pulleys. Then crank the cast-in nut just a little clockwise (same motion as before with the old tensioner) to the point where you can easily slip the pin out, thereby letting the tensioner extend so that the wheel goes down to where it puts tension on the belt. Start the engine and make sure all is turning smoothly. You are done.
 

rmchambers

Well-known member
Joined
Apr 25, 2010
Location
Stratford, CT
TDI
2003 Jetta GLS TDI
Phew....

This was a great thread, I just got done with an alternator pulley/idler/tensioner/serpentine belt replacement.

Had the extra knock noise from the passenger side and the bushing on the tensioner shock had self destructed and the tensioner was jumping around.

Quick look in TDICLUB forums and I see the answer. Got the tensioner, alternator clutch and the metalnerd tool and got to work.

I tried to do as much as I could from above before I jacked the car up and took the skid plates off, kinda stupid because once I was underneath it went a whole lot quicker. It took me a good few hours to get it all done but it's finished now and the rattle from the tensioner is gone so life is good.

I found that regular wrenches with the slight offset are a PITA for this job. I found some ratcheting wrenches in 17mm and 12mm which are straight and those really helped with the tightening of the pulley on the alternator.

thanks everyone! the step by step and the belt diagrams came in very handy.

Robert
 

kurtisk

Active member
Joined
Nov 17, 2002
Location
Tampa, Florida
TDI
2015 Passat SEL TDI, red on black, Stock; 2000 New Beetle TDI Auto swapped for 5spd, Cybergreen on Black, PSI Power Box; 2015 Golf Sportwagen SE TDI, red on tan; 2014 Beetle Convertible TDI Premium Edition, pearl white on black leather
WARNING! Tensioner bolts are EASY to strip out!

This post was very helpful, and the job is quite easy to do. My 17 year old son was able to do it himself (even with his self-doubt, angst, and pessimism. When I came out to help and 'snugged up' the longest of the tensioner bolts, it just stripped out. Then I was sorry I helped.:( Apparently the bracket the longest bolt threads into is as thick as the others and most people who strip one, strip the longest one.

Then I found the MANY posts about how to repair a stripped bolt on exactly this repair. Some suggested a helicoil, but most suggested a 3/8" tap which doesn't require any drilling. I used a 3/8" tap and a 2.5" x 3/8" bolt with lock washer from home depot. We removed the belt and tensioner to tap the hole. The set included a drip bit which already fit into the existing stripped hole, so I just had to carefully turn the tap into the hole with a 5/16" wrench and my son under the car helping to keep it straight when getting it started. This was tedious but worked without any problems. Then drilled out the hole on the tensioner to allow the larger bolt. Went pretty easy and seems to work perfectly so far.

I wish I had read something in this thread warning that stripping out a bolt was a risk. Now you are warned and know that there is a simple repair even if you are unlucky and make a mistake.

Great pictures and post!!
 

Miyagi

Member
Joined
Mar 2, 2005
Location
Sacramento area, CA
TDI
01' Golf GLS 4-dr
I took out the windshield fluid reservoir, to get at the (3) 13mm bolts. Made it easier to see what's going on, and get at them from the top of the engine.
 

ki4dfg

New member
Joined
Dec 17, 2016
Location
Alabama
TDI
2000 Jetta
Tensioner Pulley

Stupid question I am sure, but the roller on the tensioner should spin pretty freely right? I went to replace my idler roller and started to check tings out and noticed the roller on the tensioner is stiff. I ordered a new tensioner this afternoon.
 

TDIGAZ

Veteran Member
Joined
Jan 15, 2008
Location
Eastern Ontario, Canada
TDI
Current: 2003 Jetta GLS Grey 5 spd. Previous: 2003 Jetta GLS Silver 5 spd (lost in a collision)
Stupid question I am sure, but the roller on the tensioner should spin pretty freely right? I went to replace my idler roller and started to check tings out and noticed the roller on the tensioner is stiff. I ordered a new tensioner this afternoon.
Yes, it should spin freely. You can remove it from the tensioner and try cleaning it up and re-lubing the bearing to see if frees up. Also, be sure not to over-tighten the three mounting bolts for the tensioner (I believe it's 18ft_lbs), as the accessory bracket can be easily stripped... don't ask me how I know.
 

ki4dfg

New member
Joined
Dec 17, 2016
Location
Alabama
TDI
2000 Jetta
Thanks! I ordered a new tensioner. At 398,000 miles on the engine - I am not sure if it was replaced on the last timing belt replacement or not.
 

jaredaggie

Well-known member
Joined
Nov 11, 2011
Location
Aggieland, Texas
TDI
2000 ALH, Black, 5M; 2013 Passat TDI 2.0 6MT
Couple years has passed but I wanted to thank the OP for this great write up. In my instance the idler pully just broke into many pieces. Of course I replaced the tensioner and serpentine while it was all off. Excellent write up, thanks again to all who contribute to this site.
 

jokila

Vendor
Joined
Dec 3, 2004
Location
Houston, Texas
TDI
2003 Jetta GLS, Manual
My idler pulley fails on average about every 100K miles or so. Don't know why that is. The last time I bought one from Autozone because I was stuck 4 hours from home. I know the cap is important to use to keep debris and general moisture from reaching the bearing in some way. I use a skid plate for about 5 years now.

There is a post above that claims over torquing the bolt that holds the idler pulley will cause premature wear, but I don't buy that as a reason. Truth be told, I never use a torque wrench on either one of these parts. I don't over torque them in my opinion and have had to repair a damaged thread as the tensioner came to me being held in place by two bolts.
 
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Keven

Veteran Member
Joined
Jun 16, 2008
Location
Tampa FL
TDI
2000 Jetta TDI
I realize this is a bit vague but I'm trying to help my parents across the state. I've been telling my parents for about a year that they needed to replace the idler pulley on the 2002 wagon tdi they have. Apparently it finally grenaded but I am getting conflicting statements about what actually broke. Their mechanic is saying it's 8 hours worth of work to fix and the timing belt has to come off. Based off what I am familiar with the idler pulley and tensioner should only be a couple hours worth of work. I'm wondering if the pulley took out some bracket when it failed because my dad keeps saying the piece with the "honeycomb" is what needs to be replaced.

Is this ringing any bells with anyone?
 

alex_tdi

Veteran Member
Joined
May 15, 2001
Location
Los Angeles, CA
TDI
TDI GLS, 2001, Blue
Maybe the mechanic is thinking the pulley that's part of the timing belt. If that blew up, then the engine would already be a goner, not an 8 hour job.

If it's the idler pulley for the serpentine belt, it should NOT take 8 hours for anyone who's done it before. I did it in about 2 hours on my first try.

If you get the serpentine belt tool that's available as a free loaner tool from Autozone or other part dealers, it's super easy to get into the tight space to loosen the tension. I also find the "Long Reach Dual Head Ratchet" from Harbor Freight to be really helpful for the actual bolts.
 

atmarine

Veteran Member
Joined
Mar 24, 2013
Location
Ny state
TDI
'99 Golf 5 speed
How long does the serpentine belt and tensioner hardware typically last? I’ve replaced it all 60K ago, and now have it all apart for a different reason. Ive got a new belt and shock and am debating g putting the new in now, or reinstalling the old. The old looks in good shape so it’s a tough call.
 

Bengoshi2000

Veteran Member
Joined
Jun 24, 2013
Location
Triad NC, USA
TDI
2002 Golf (0M1)
How long does the serpentine belt and tensioner hardware typically last? I’ve replaced it all 60K ago, and now have it all apart for a different reason. Ive got a new belt and shock and am debating g putting the new in now, or reinstalling the old. The old looks in good shape so it’s a tough call.

I'd go ahead and install the new bits. The last tensioner pulley/shock I put in my golf got just about 65,000 miles (the tension was fine, but the bearing in the pulley was "wiggly" and the rubber in the shock mounts was done).
 

Den

Veteran Member
Joined
Apr 15, 2001
Location
Central Fla.
TDI
2001 Jetta Baltic Green & 2015 Passat SE TDI 6 spd. auto.
Any one have a problem keeping the belt on the pulley, mine keeps running off the pully by two groves, not sure why as of this posting.
 

werdna

Veteran Member
Joined
Aug 14, 2009
Location
An obscure corner of northeastern Massachusetts
TDI
2003 Jetta Wagon, 2013 Touareg Sport, 2015 GSW
In case this helps somebody:

The INA idler rollers that everybody(?) sells seem to have changed style a bit. The hub of the bearing has a significantly larger diameter (larger bearings yay), but also it's no longer symmetrical. The side of the bearing that sticks out more is the side that goes against the bracket, and the bolt goes in the other (more recessed) side. If you're swapping in one of these for the old style I would make sure to clean the road grunge off of the area where it rests on the bracket, since the new hub is bigger than the old one.

At least on my engine there's a significant section of roller extending beyond the belt that the belt doesn't ride on, while the belt is *very* close to the edge on the inside/engine side of the roller. Made me think I had it on backwards, but if you try it the other way (so the roller is closer to the engine) the roller hits the bracket before the bearing hub makes contact. (Also the dust cap won't fit.)

85k and four years on this one. (At some point I lost the bearing cap which surely didn't help.)

Also if you run a panzer plate I suggest removing the front right support entirely, it makes this job a lot more tractable; you really want to be able to go straight onto the roller bolt and seat as well as possible. Removal torque is right at the edge of where I'm taking bets with myself on whether it's going to release or strip the head. (Bad flashbacks to the 1.6 alternator pivot bolt setup in the A2s!)
 

KingJ416

Active member
Joined
Dec 26, 2021
Location
Canada
TDI
2001 volkswagen jetta TDI
Very helpful! I'm trying to get my serpentine belt on but the cast nut on the tensioner seems to be pretty stripped due to my cousin trying to use an adjustable and a wrench with an angled end last time.. 😒😔 Any ideas?
 
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jokila

Vendor
Joined
Dec 3, 2004
Location
Houston, Texas
TDI
2003 Jetta GLS, Manual
Very helpful! I'm trying to get my serpentine belt on but the cast nut on the tensioner seems to be pretty stripped due to my cousin trying to use an adjustable and a wrench with an angled end last time.. 😒😔 Any ideas?
Yeah. .you want to use a high quality 16mm socket when handling that nut.

Swap it out for a better one or file the nut faces to make it a 15mm size. I've never done filing but you don't have much in choices on the ALH tensioners.
 
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KingJ416

Active member
Joined
Dec 26, 2021
Location
Canada
TDI
2001 volkswagen jetta TDI
Yeah. .you want to use a high quality 16mm socket when handling that nut.

Swap it out for a better one or file the nut faces to make it a 15mm size. I've never done filing but you don't have much in choices on the ALH tensioners.
You mean swap the tensioner completely? And ya might have to try the file thing for now. Hoping I can get it done with some help.... but yes I'll be looking into replacing it next.
 

KingJ416

Active member
Joined
Dec 26, 2021
Location
Canada
TDI
2001 volkswagen jetta TDI
Well t
Worse comes to worst, you could cut the belt and replace the whole tensioner assembly.
The belts is off. I'm tryna put it back on lol I did a power steering pump replacement. Would just need a new tensioner
 

KingJ416

Active member
Joined
Dec 26, 2021
Location
Canada
TDI
2001 volkswagen jetta TDI
So I picked up a new serpentine belt today and the old one can literally fit inside of it.

Still dealing with the stripped tensioner nut but feeling pretty confident about getting it done finally Though!

Gunna try a 15mm wrench or 9/16" and if not then I'm gunna take some time to give it a file and hammer on an adlustable... wish me luck!! 🤞🙏🧰🔨🔧
 

KingJ416

Active member
Joined
Dec 26, 2021
Location
Canada
TDI
2001 volkswagen jetta TDI
Just out of pure curiosity... when I had some1 ask an auto parts shop about the tensioner, I was told they didn't have it but that they had the idler pully/assembly.

Now I have 5 pulleys. I thought - engine crank, power steering, alternator, tensioner, and ac... -

but I've heard of an idler pulley before somewhere Too. Am I just incorrect, or is that on a non-alh engine or something?
 
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