Timing belt installation: VW Jetta TDI AHU engine and VW Passat 1Z- part 2

Nov 8, 2013
Timing belt installation: VW Jetta TDI AHU engine and VW Passat 1Z- part 2
  • Jetta and Passat timing belt part 2 - installation - for 1996, 1997, 1998, 1999 VW Jetta TDI and VW Passat 1Z and AHU engine
    Back to the mk3 FAQ and "how to" index page
    difficulty 3/5


    This article shows some tips for timing belt installation for the VW Passat or Jetta mk3 TDI.
    Also see: 1000q: timing belt removal for 1Z/AHU TDI , 1000q: water pump removal , 1000q: intermediate shaft seal , and 1000q: injection pump removal or mk4 ALH pump swap.


    First review 1000q: 1Z/AHU engine timing belt removal for mk3 jetta and passat TDI. Also see 1000q: torque wrench FAQ for tips on torque wrench use.

    Double check that the camshaft lock and injection pump lock are in place. Place feeler gauges under the camshaft lock to center it as much as possible. The metalnerd tool comes with 2 business cards - the paper should compress just enough to let you tap the camshaft lock into place.


    Also check that the engine is at TDC. TDC mark is shown below and after I painted it.
    [​IMG] [​IMG]

    Install the idler pulley (13mm bolt, 18 ft-lbs) and TB tensioner (13mm nut, loosely hand tight only for now).

    Double check that the TB tensioner tab is firmly in it's alignment hole or else the tensioner can fail. Only loosely hand tighten the TB tensioner nut since you want the center to be able to rotate. Sorry for the lack of a pic in context, below is a picture of the rear timing belt cover off the engine showing the alignment hole.
    [​IMG] [​IMG]

    Slip on the timing belt starting with the crankshaft sprocket and injection pump sprocket. Once the teeth are on, slip the camshaft sprocket onto it's tapered end. The camshaft sprocket should be free to rotate even though the camshaft is locked. Most of the belt slack should be at the tensioner.

    Put on the camshaft bolt (19mm) but don't tighten it, just put it on to catch the sprocket in case it pops off.

    Double check that the engine is at TDC with the camshaft and injection pump lock pin in place. Now remove the injection pump lock pin only.

    Note: I suggest removing the injection pump lock pin before tightening the tensioner. This is the order that the service manual says. More detail is listed on the first page's introduction - caution.

    Use a spanner wrench clockwise to tighten the TB tensioner until the alignment marks are lined up. CAUTION - Although it's possible to tighten the tensioner in a counterclockwise direction, this is wrong, only tighten in a clockwise direction! It should stay aligned without counterholding the 13mm nut. Once aligned, tighten the nut to 15 ft-lb. Then double check that it's still aligned and that the alignment tab on the back is still in place. Below is a video of tensioning an ALH VW TDI engine (not yours) timing belt tensioner that will move in a similar fashion. Click the play button (the triangle that points to the right) to view the video. The button to the right of "HQ" will switch the video to full screen. It's normal for the camshaft sprocket to rotate during tensioning.

    Note: The Bentley service manual calls the tensioner nut a locknut in one place, clamp nut in another, and mounting nut in the third reference. The parts diagram just calls it a nut. I would apply a tiny dab of light strength threadlocker to the nut to make sure it won't fall out. Threadlocker could change the torque spec so refer to your product's spec sheet to see how much to change the torque spec. The permatex blue (medium) threadlocker spec sheet doesn't call for adjusting the torque spec.

    Here is a picture of the tensioner and a closeup of the alignment marks when you install it (before tightening, not lined up). The raised dash and the notch highlighted below will come into alignment as you tighten the tensioner clockwise with the spanner wrench.
    [​IMG] [​IMG]

    Note - the engine should be cold when setting the tensioner. It automatically adjusts to temperature so don't be surprised if it's off when checking it later on a warm engine. If you want to retighten it later, loosen it all the way before retightening it.

    You can now tighten the camshaft sprocket bolt, pictured below, to the factory value of 33 ft-lbs but see the caution below! Remember to counterhold the sprocket when you tighten the bolt! You can remove the camshaft lock now or later, just make sure to not torque against the lock or else it could crack the camshaft!

    CAUTION - Make sure that the tapered conical tip of the camshaft is clean and dry of any oil or grease because damage to the threads, tapered camshaft end, or an oiled taper, can change the force on the taper and result in a spun camshaft sprocket and engine damage! I use a slightly higher torque spec of about 36-40 ft-lbs on the camshaft sprocket bolt. This is only about a 10-20% increase in torque over the factory value. The reason this caution has been added is because there have been multiple reports of spun camshaft sprockets on ALH engines when torqued to only 33 ft-lbs. I have not heard of this problem on 1Z/AHU engines but it couldn't hurt. Regardless of the cause (faulty torque wrench, user error, greasy camshaft taper, etc.,), a slightly higher value on this bolt will not damage the camshaft end, sprocket, or the 19mm sprocket bolt, but will add a margin of safety against a spun sprocket. I believe that this range is a very safe balance between spinning the sprocket and any possible damage to the camshaft or sprocket.

    Here is a breakdown of the components so you can decide for yourself: the bolt, the camshaft threads, the camshaft taper, the sprocket, the belt position.

    The 19mm camshaft sprocket bolt is large compared to the low torque value of 33 ft-lbs and will not be damaged by a small increase in torque value. Later BEW engines use a torque of 74 ft lbs on an identical bolt. Although the camshaft is different and setup is different, the bolt is the same.
    The camshaft threads are not brittle enough to be damaged by a 15% increase. As a matter of opinion, I do not go over 40 although others have tested the camshaft to well over 50 ft-lbs without any damage to the threads when using proper tools and pullers. A very high torque could cause some damage.
    The taper is also strong and it is not likely that it will be damaged or deformed by a small increase. A much higher torque could deform the taper but a small increase isn't going to do any damage. Of course whacking the sprocket with a hammer or improper removal can cause damage so always use a puller or the method in the factory service manual.
    There have not been any reports of damage to the sprocket due to a slightly higher torque.
    The belt position on the sprocket is not dictated by the sprocket and is unchanged.
    In the end, the torque spec that you want to use is up to you. The increase is not proven to cause any damage so I would rather err on the side of caution. More torque isn't better but there are rare but catastrophic spun sprockets on ALH engines when torqued to only 33 ft-lbs. The 1Z/AHU engine is different and for unknown reasons, spun sprockets don't seem to happen on these engines. It's your engine and myturbodiesel is not responsible for any damage as a result of the information found on this website, etc.,...see the disclaimer in the TOS Agreement for the full legal disclaimer.

    Double check for TDC. If it's fine, remove the camshaft lock if it's still in.

    Put the transmission in neutral gear and rotate the engine twice by hand. I suggest using the 19mm crankshaft bolt to turn the engine over. The point of turning the engine by hand is to check for any mechanical interference without damaging anything. Do not use the the starter since if there is some problem, the start is strong enough to cause damage.

    Do not use the injection pump sprocket to turn over the engine even though it has a lot of teeth engaging the timing belt. The reason why is because it has to work against the resistance of the valve springs and if you attached the power steering belt and serpentine belt, it can cause the belt to jump the injection pump sprocket. The camshaft sprocket is a better choice because you aren't working the stress of the valve springs against the belt. I believe that the crankshaft bolt is still the best choice but do not apply any significant force to it since it's a stretch bolt. You should feel light resistance as the engine builds compression. If it seems jammed, double check that the camshaft and injection pump locks are removed and the transmission is in neutral, this could also be a sign that the valves are hitting the pistons.

    Put the engine back at TDC and double check the injection pump and camshaft locks. If they fit correctly, the belt is on correctly. If the camshaft lock won't go in at TDC then loosen the sprocket and tensioner and reset the belt. If the camshaft lock fits at TDC but the injection pump pin won't go in, adjust the injection pump's position as described below in "Adjusting injection pump timing" until the pump pin will go in. This is what the service manual says and you will fine tune the pump position later anyways. If it's too far off then the injection pump sprocket could be a tooth off.

    Put the valve cover and lower timing belt cover back on. Note: the Bentley service manual says the torque for the lower cover bolts/nut is 18 ft-lbs. This is a typo because it's too much force, especially since it also says 10 Nm, which is 7.3 ft-lbs, not 18 ft-lbs. Reinstall the airbox, accordian hose, and upper timing belt cover.
    [​IMG] [​IMG]

    Again, if you have no bolt at the red arrow pictured above, you could insert a self tapping screw of the correct diameter in there to hold the lower cover on. I tried a screw but it wasn't secure enough so I used 4 zip ties because it's very difficult to get a bolt in through the back. I threaded a zip tie inserted through the timing belt side and then used it to pull 2 zip ties back through the dipstick side. Putting a cut off zip tie head on each tie held it in place firmly. 1 doesn't work too well - using 2 ties lets them push against each other. In addition, if they melt and fail, they are plastic and shouldn't damage anything (it will not fall onto the timing belt). Pictured below left is the 2 zip ties with their heads on the other side. Pictured below right is 2 more zip tie heads securing the first 2 zip tie tails. The part number for the missing t-head screw is VW # n 900 534 01 but don't bother ordering it unless you can figure out how to insert it from the rear or if the full water pump housing is removed.

    Reinstall the crankshaft pulley/harmonic balancer, v-belt and serpentine/alternator belt.

    To tension the power steering v-belt, torque the splined tension adjuster to 2.9 ft-lbs for used v-belts, 5.1 ft lbs for new v-belts and then torque it's bolt to 18 ft-lbs. The v-belt should have about 5mm of deflection in the middle. The torque for the four harmonic balancer bolts is 15 ft lbs. Also install the lower engine bay cover.


    Checking injection pump timing

    You will now want to check the timing of the injection pump. If you don't have a VCDS but the engine starts, you can skip this for now but it's important to at least check this later. Find someone who has a VCDS if you don't want to buy one. Because the pump is electronic, you must use an interface to adjust it.

    Caution: when the engine is running, make sure any bolts/tools/fingers are clear of all belts or radiator fans. The moving belts or fan can easily rip off your hand or fingers if they get caught in the belts or fan! See the TOS Agreement for the full legal disclaimer.

    To check the timing, warm up the car. Plug in a VCDS. In the passat, the plug is to the left of the stereo, in the jetta it is behind the plastic panel above the cigarette lighter spot.

    Enter "basic settings", group 1 or hit enter. A button should appear "TDI timing". This brings up a graph. Caution: the graph has different settings for which car you have. Make sure to select either 1Z or AHU engine, otherwise timing may be off. You want to be above the middle line but below the top line. This means that you have slightly advanced timing. This will give easier starting, more power, and better fuel economy. If it is not, then you may want to adjust the timing. The VCDS obd2 plug location is pictured below.
    [​IMG] [​IMG]

    Adjusting injection pump timing

    To do adjust timing, remove the upper timing belt cover with the engine off.

    Slightly loosen the 3 nuts/bolts that hold the injection pump in front and the 1 bolt that holds it in the rear. If the bolts are too loose, the pump timing will jump from the top of the graph to the bottom - small adjustments make a big difference. 1 of the front bolts and the rear bolt is circled below in the picture. The other 2 that are not circled are nuts and accessed (with engine off) through the timing belt side. The pump was removed in this picture. The mounting holes on the injection pump are elongated so that you can rotate it slightly.

    You may also have to loosen the fuel injector hard lines at the injection pump and fuel injectors. Make sure to counterhold the union so that they don't spin in the pump. I suggest a single drop of PB blaster at each union-line thread to help loosen them.

    Rotate the entire injection pump on its mount (the pump's shaft will rotate against the pump's body) to adjust timing. As long as you don't loosen the bolts too much, you can do this with the engine running and see live changes in the timing graph. Pushing the pump towards the engine advances timing and moves it higher in the timing graph. Pulling the pump towards the radiator retards timing and moves it lower in the timing graph. Slightly advanced timing (above the center line) will result in slightly higher EGT, slightly more engine stress, but better fuel economy and power, and easier cold starts. Slightly advanced timing is preferable to slightly retarded timing although anywhere within the boundaries of the chart is considered acceptable.

    Here is a front view, you do not have to remove the sprocket, the sprocket was removed for illustrative purposes only and was from an earlier step. Obviously your timing belt, rollers, etc. will all be in place.

    Once you are satisfied, tighten the injection pump bolts to 18 ft-lbs and reinstall the timing belt cover. Again, I suggest placing the timing between the middle and upper lines so that it is slightly advanced but still within the limits of the graph.