The timing belt (TB) connects the camshaft (opens the valves) to the crankshaft (moves the pistons). In the mk3 TDI it also moves the intermediate shaft and the injection pump. All TDI engines are interference engines. If the TB slips at the crankshaft or camshaft, it's very likely that the valves hit the pistons and cause head damage and in severe cases, piston/rod damage. If it slips at the injection pump but the crank and camshaft are OK, it can cause engine stalling but this is less likely than valve-piston contact. There is no warning whatsoever when a TB is worn out and is ready to slip. If there is any question as to when the TB was done or if it was done correctly, replace it ASAP. Most maintenance items are as soon as practical, if the TB or tensioner/idler pulley breaks, you could even need a new engine under the worst case, so change it as soon as possible. Disclaimer- this article is revised and updated to include the most current information but is not a substitute for the factory service manual! See the TOS Agreeement for the full legal disclaimer. Although a timing belt job can successfully be done with basic tools and mechanical experience plus the timing belt tools, improper installation of the timing belt can cause severe engine damage! Take all precautions listed in the factory service manual. If you have never worked on your car, I suggest gaining experience with easier projects first before doing something as critical as a timing belt!
Suggested while you are in there: replace your old harmonic balancer (aka the crankshaft / serpentine belt pulley) with the updated part since it will be removed anyways. Over time, the rubber damper in the pulley dries out and causes a chirp-chirp noise on cold starts. See 1000q: chirping noise on cold start for more info on that repair. Suggested maintenance at your discretion: water pump, camshaft, and intermediate shaft oil seal. The intermediate shaft is the shaft inside the engine that drives the oil pump. It uses the same seal as the camshaft - also replace the o-ring under the intermediate shaft seal flange. I would not change the crankshaft front seal unless it is leaking oil.
Differences in procedures between this and similar mk3 TDI timing belt writeups: Do not use the camshaft bar or injection pump pin (and the timing belt) to counterhold against the engine when tightening or loosening the crankshaft pulley bolts. The camshaft bar says "not for torque". Different suggested torque spec for the camshaft bolt. Use a wood block to tap off a stuck valve cover instead of a screwdriver since it could scratch the metal. Other writeups suggest to set the tensioner with the injection pump lock in place. This writeup follows the Bentley manual - remove the injection pump lock pin after the belt is on but before setting the tensioner, details below.
Caution: the order of steps listed in this writeup is the same as the Bentley service manual but different from older writeups you may see elsewhere. Other writeups tell you to set the tensioner with the injection pump lock in place. This writeup follows the Bentley manual - I suggest removing the injection pump lock pin after the belt is on but before setting the tensioner. The Bentley manual says on page 23b-9 describing timing belt installation: "Remove the locking pin from the pump sprocket. Tension the belt by turning the semi-automatic tensioner with a spanner tool clockwise until the notch and the raised mark are aligned." While this is listed in the same step number and could be open to interpretation, the order is confirmed in another section where it describes injection pump installation (page 23b-12). One step says to remove the locking tool and then a few steps later, to then tighten the tensioner. Because both procedures list the same order, my interpretation of the service manual is correct - remove the pump locking pin before tensioning the belt. This means other writeups do not follow the service manual. However, there are also some confusing instructions in the service manual detailed below.
Why I follow the order of steps in the manual: My interpretation of the service manual is correct but why follow the service manuals steps? Later ALH engine TDI let the injection pump sprocket move even with its lock in place so that the tensioner spreads tension evenly across the timing belt when you set it. I believe that removing the injection pump lock pin before tightening the tensioner serves the same purpose in these earlier TDI - it lets the sprocket move a little bit if needed. It doesn't move much but it could move a little. In a later step you turn the engine over twice by hand to double check for interference. The service manual says that if the pump pin doesn't go in then loosen the pump bolts and rotate the pump until the pin does go in.
Confusing instructions in the Bentley manual: One confusing point is that if the pump pin is off and won't go in, (assuming TDC and camshaft positions are correct), rotating the pump won't fix the sprocket's hole being off. The pump's shaft-sprocket relationship is locked with a woodruff key. Rotating the pump won't move the shaft much since the shaft moves freely inside the pump. Because the shaft won't move the sprocket shouldn't move (without moving the timing belt) and the pump pin won't go in if it didn't go in before. If the pin is just a hair off, my suggestion is to ignore it since you'll adjust the pump in a later step anyways. If the pin is off by more then a hair, the timing belt is probably off by a tooth.
Another confusing point is that the procedures for timing belt installation under the different sections "to install injection pump" and "to install camshaft/injection pump drive belt" (timing belt) are different. While both say to remove the injection pump pin before tensioning the belt, one procedure says to have the pump mounting bolts hand tight before tensioning the belt while the other does not say to loosen them in the first place (it does say to tighten them but I think it's a typo, see below). One says to turn the engine over twice by hand to double check your work (I would definitely do that), the other doesn't.
Possible typo in "to install camshaft/injection pump drive belt": The manual also states: "Tighten the.....injection pump sprocket mounting bolt" and then lists its torque as 18 ft-lb. The injection pump sprocket mounting bolt's torque is 41 ft-lb, not 18. I believe this is a typo that should read "injection pump mounting bolt" instead off including the word sprocket because the torque for those is 18 ft-lb. As mentioned above, the instructions for installing the timing belt never say to loosen these bolts in the first place but instructions for injection pump installation do say to loosen them and have them hand tight. There's a confirmed typo for torque spec on the lower timing belt cover bolt, it's noted on the next page.
If you find the tips on this page helpful, please use the donation button at the top so that I can continue to keep publishing great articles for free. The Bentley service manual is about $80 vs. this page with more pictures, color pictures, and greater detail. Thanks in advance!
So what should you do? The procedures listed here follow the order of steps in the service manual while interpreting its inconsistent instructions and typos. This interpretation of the service manual may not be correct but it's what I do and my car is fine. This website is not responsible for your work and the only official instructions are the ones listed in the Bentley manual, etc., read the TOS Agreement for the full legal disclaimer.
Parts (click links to compare current prices)
CAUTION - generic parts available on ebay or other online sellers may
be of questionable origin. The below linked sites are all well known and
experienced TDI vendors.
CAUTION - I would not buy the or any other of this seller's copycat sites' timing belt kit. These are almost certainly low quality copycat parts! It's not worth saving $50 when it can result in thousands in engine damage! I also had a bad experience with this seller so never again. The timing belt tool kits are reported to fit poorly or not at all.
timing belt kit OR the individual components. Kits available at dieselgeek or kermatdi
timing belt 028 109 119 P
timing belt tensioner 028 109 243 F
timing belt idler pulley 028 109 244
4x allen bolts (6mm) for harmonic balancer pulley (crankshaft pulley / serpentine belt pulley) VW# n903487-04 (may have been superceded by n903487-06)
10, 13, 16, 18, 19 mm wrenches/sockets
tensioner spanner wrench VW tool #T10020, or equivalent
camshaft setting bar/lock VW tool #2065a , or equivalent
injection pump locking pin VW tool #2064, or equivalent
sprocket counterholding bar (included with the metalnerd tools, metalnerd #MN3036)
pics and measurement of TB tools by Ray_G (mk4 ALH engine tools also shown but not used on this engine, (pictured below as thumbnails, click to enlarge)
Optional parts (click links to compare current prices)
lower crankcase vent (CCV) breather hose (in case yours is brittle, see note below) VW # 028 103 491 J
new harmonic balancer pulley (crankshaft pulley / serpentine belt pulley) VW # 028 105 243T
serpentine belt and v belt
valve cover gasket (included with some kits)
light strength locktite
intermediate shaft/camshaft gasket VW# 068 103 085E
intermediate shaft seal flange o-ring VW # N 903 535 01
PB Blaster, liquid wrench, etc., penetrating lubricant
EZ out - for removing stripped allen bolts (pictured below, can be deep or shallow)
If you are changing the water pump then also get some G12 coolant to replace
lost coolant. I suggest 3 liters of coolant or 1 gallon and an equal
amount distilled water for the timing belt job and to account for spilled
coolant. Do not use generic green coolant, see 1000q:
water pump change for more details.
genuine VW (1 gallon size , VW #G 012 A8F A4 ) genuine VW (1.5 liter size, VW #G 012 A8F M1),available from kermatdi 1.5L size, dieselgeek (1.5 liter size, VW #ZVW 237 G12)
With the car off, in gear, and the handbrake on, raise the front of the car securely with jackstands and/or ramps or wood blocks as specified in your factory service manual. Never get under the car if it is being supported by a hydraulic jack. Secure all tires with wheel chocks, place the car in gear, and apply the parking brake.
Remove the plastic engine cover (3x 10mm nuts)
Also remove crank case vent (CCV) - caution - the lower CCV breather hose
(outlined above in yellow and pictured below) is bolted to the lower engine
block. If the top part of the hose is not soft, the bottom part will be
dried out and can shatter if you bend it! It is also a common place for
oil leaks due to a cracked flange or dried out o-ring, the bottom part often
cracks on its own after mileage and age. If you choose to replace it, (2x 6mm
allen) bolts hold it at the bottom. The part number is VW # 028 103 491 J. I don't know the torque spec for those bolts but 10-15 ft-lb should be enough since the hose is plastic and the seal is achieved using the o-ring.
Remove the upper timing belt (TB) cover, held in place by 2 metal spring
clips and a screw.
On the valve cover, remove the plastic thread protectors by prying them
off. Underneath, there are (3x 10mm) nuts and washers that hold the valve
cover. Under those, there is a metal cup and rubber gasket. Don't
remove the bolt that's under them all. You can now remove the valve
cover. If it's stuck, tap it at the flange with a piece of wood. Avoid
prying with a screwdriver since this can scratch the sealing surfaces.
You can reuse the valve cover gasket if it's in good shape.
Go underneath the car and remove the plastic lower engine bay cover.
Remove the power steering v-belt and alternator serpentine belts.
Although the service manual says to do this in a later step, I
think it's best to do this now. It makes turning the engine over much
easier and it avoids turning
the power steering/alt, etc., opposite their normal wear and rotation.
There are 2x 13mm bolts holding the power steering pump and 1x 16mm bolt
holding it in the back. Loosen these and then push the power steering
pump towards the rear of the car to slip off the v-belt.
Remove the serpentine belt by relieving the pressure off the belt. You
can use a wrench to move the tensioning lever arm while you slip off the
belt. Although the service manual says to use the idler pulley's bolt to
move the lever, I
don't do this because it can strip the bolt. The below picture is from
another writeup, ignore the red arrows, you don't have to loosen those.
Just put a wrench on the lever on the other side of the red arrows.
Remove the harmonic balancer/crankshaft pulley and the v-pulley sitting on top of it (4x 6mm allen bolts).
Caution: The pulleys you are removing are the v-pulley and the serpentine belt pulley only, this is pictured below! Do not remove the crankshaft sprocket (the one that looks like a gear and drives the timing belt). Its bolt (the 19mm 12 point bolt) is a one use only stretch bolt so don’t remove it. If your TDI is making a squeaking or chirping sound on cold starts, see 1000q: cold start chirp fix. The pulley design was changed to fix the chirping noise.
This pulley doesn't drive the timing belt, it only drives the power
steering, alternator, water pump, air conditioning. The pulley’s allen bolts may get stripped so I suggest
putting a few drops of PB Blaster or liquid wrench under their heads. Let
it soak since PB Blaster needs time to penetrate the threads. I suggest lightly tapping the allen bit with a hammer to make sure it's seated all the way
in - this helps avoid stripping. If they do get stripped, a sharp EZ-out
should remove them easily.
I suggest putting the car and gear and having someone step on the brakes as the primary method to counterhold against the 4 allen bolts. If it's still moving, use the 19mm 12 point center crankshaft bolt to counterhold. I don't suggest using the 19mm 12 point bolt as the primary method to counterhold because the bolt is a 1 use only stretch bolt and the force required to loosen the allen head bolts can be high. The Bentley service manual does not give details on how to counterhold these bolts, it just says to remove the crankshaft pulley. Although later ALH TDI engines can use the 19mm center crankshaft bolt for counterholding, its bolt/crankshaft is different and is torqued to 89 ft-lbs + a turn vs. your bolt which is torqued to only 66 ft-lb + a turn. Having a helper step on the brakes is also easier than holding two tools in a limited space anyways. Other articles you may see elsewhere say to use the timing belt tools to counterhold, I do not suggest this due to the amount of force involved. Your tool also says "not for torque" on it. Using the camshaft lock to counterhold can crack the camshaft.
Remove the lower TB cover. You should now be able to see all of the
Caution - the TB cover is held by
2x 10mm bolts and 1x 10mm nut. The bolt holding in the nut shouldn't fall
out but mine was already missing. Shown
below (red arrow) is another car that did have the bolt. When you remove
the timing belt cover, take care to not knock that bolt loose since it's very difficult
to insert a new one. If you have a magnet, use it to pull the bolt
forward and hold it in place. The reason I removed the airbox was so that
I could stuff gasket maker around the bolt. This will prevent it from
backing out when you put the cover back on and can be easily removed later if
you choose. More tips on this in 1000q: timing belt part 2 -
With the transmission in neutral, turn the engine over to TDC by turning the
19mm 12 point crankshaft bolt. This is what is recommended by the service
manual. You can also use the sprocket counterholder tool on the
camshaft sprocket to turn the camshaft clockwise until the camshaft's alignment
slot is horizontal. I suggest doing this now (after removing the
v-belt/serpentine belt) because the belts add resistance and it'll be easier to turn the
sprocket after they are removed. You will insert the camshaft lock later -
the slot provides a
general reference of where TDC is. (pictured below, the reason why the tool
doesn't look like the ones pictured above is that it's a metalnerd tool instead
of a VW tool)
Although the below picture is from a later TDI, the camshaft looks the
same. Both of the camshaft #1 lobes (closest to passenger side on a North
American left hand drive car) should be pointing up. The reason why the
camshaft lobes should be pointing up is because this indicates that they are
not pushing open the valves. The camshaft lock should fit in the machined
slot at the other end of the camshaft. If the camshaft lock is in and the
#1 lobes are pointing up, the TDC mark on the flywheel should be close to the
viewing window on the transmission.
Remove the top dead center (TDC) plug. It's located at the center-top
of where the transmission meets the engine. Rotate the engine to get the
TDC mark on the flywheel to align with the TDC pointer mark on the transmission
bellhousing. Sometimes the pointer on the transmission bellhousing
is worn like mine, the TDC mark should be at the center of the window. If
you don't see it, try turning the crankshaft pulley 1 full
You can mark it with paint or chalk for faster identification
Counterhold the camshaft sprocket while you loosen its 19mm bolt. You
can put the camshaft lock in place but be very careful not to put any torque on the
lock or else it could crack the camshaft. If you're not sure of the
amount of force involved, I suggest test fitting the lock and putting it back
after loosening the camshaft bolt. Since the camshaft sprocket is a
tapered fit onto the camshaft, loosening the bolt will not release the sprocket
yet. (note - this picture was taken during camshaft tightening, don't use
a torque wrench for loosening)
After loosening the bolt, turn the 19mm bolt out halfway to catch the
sprocket when you pop it off in a later step.
Recheck TDC and insert the camshaft lock plate. For best results, put a business card or feeler gauge under
each arm of the camshaft lock so that it's as even as possible. If you
have a crankshaft lock, insert it now and check that the flywheel mark is still
Loosen the 13mm bolt holding the TB tensioner and rotate it counterclockwise with a spanner wrench or VW tool #T10020 (you can use an adjustable spanner wrench) to loosen. Always loosen counterclockwise and always tighten clockwise. Note - if you later want to check the tension of the tensioner, do it on a cold engine and don't be alarmed if it's a hair off. If you want to tighten it, make sure the timing belt won't move around and then loosen the tensioner counterclockwise all the way before retightening it to the marks. Not loosening it before retightening it can cause damage.
You should be able to
insert the injection pump sprocket lock (indicated below w/red
arrow). If it's a mm of so off, don't worry about it, just move the
sprocket a little to get the tool in. If it's as much as 1cm off, make
sure the engine is really at TDC, the camshaft slot horizontal, and the hole
correct. It's possible the belt was a tooth off if it was that far off.
Use a punch through the hole pictured below to tap off the camshaft
sprocket. This will release the sprocket.
You can now remove the timing belt.
Remove the camshaft sprocket, TB, TB tensioner (13mm nut) and idler pulley
(13mm bolt). Leave the injection pump lock and camshaft lock in
place. These will make sure that they don't move. The flywheel and
its mark shouldn't move on its own (flywheel is
on opposite side of crankshaft from crankshaft sprocket) and if you have a lock
it definitely hasn't moved.
If you need to replace the water pump , intermediate shaft oil seal,
camshaft seal, or injection pump, do so now. See: 1000q: timing belt part 2 -installation
, 1000q: water pump, 1000q:
intermediate shaft oil seal , and 1000q: injection
pump removal or mk4 ALH pump swap as needed.