Water pump replacement for mk3 TDI: Jetta and Passat-1Z. AHU engine

Apr 17, 2017
Water pump replacement for mk3 TDI: Jetta and Passat-1Z. AHU engine
  • Water pump replacement for mk3 diesel - VW Jetta - Passat TDI , 1z and AHU engine
    difficulty: 3/5


    Unlike later VW diesels, the water pump is not part of the timing belt but part of the alternator/serpentine belt system on the 1z and ahu engine. It can be replaced without changing the timing belt but is difficult. You only need to change the moving parts, changing the whole housing is unnecessary. It is much easier and probably faster to replace the water pump by removing the timing belt. Because of this, a new water pump is recommended if there are signs of leaking or every other timing belt change. Also note that because the intermediate shaft pulley is so close to the water pump, inspect your parts to make sure that the water pump has recessed bolts where the intermediate shaft pulley overlaps it (pic below) or else it will rub. Also see related links: 1000q: timing belt removal and 1000q: timing belt part 2 - installation.

    The intermediate shaft pulley has to be removed to get the water pump off, it's also worth it to replace the intermediate shaft if your car has high mileage. See 1000q: intermediate shaft seal replacement for more details. The intermediate shaft runs the oil pump and uses the same seal as the camshaft and crankshaft front main seal.

    This project is rated 3/5 difficulty only because of timing belt removal, changing a water pump is otherwise very easy.

    Parts for water pump (click links to compare current prices)

    coolant pump bolts #N 010 222 8 (optional, quantity: 8)
    new water pump #b 037 121 005 B you may not need the entire water pump, you may only need the water pump impeller so please check the part numbers and ask your vendor. Also make sure that the water pump has recessed bolts on the upper left side to clear the intermediate shaft pulley.
    G12/G12+ VW coolant (about 1 gallon, caution: do not mix coolant types, see 1000q: coolant flush for more details)
    an equal amount of distilled water, about 1 gallon
    water pump gasket (OEM metal/rubber water pump gasket) #026 121 041 P note: most water pump kits include a paper gasket that is appropriate for older VWs that used the same pump, it's best to get this rubber/metal gasket

    10, 18mm sockets, wrench
    6mm allen wrench

    thermostat VW# 044 121 113
    thermostat o-ring VW# 038 121 119 b (50x4)
    timing belt lower cover t-bolt VW# n 900 534 01 (don't bother ordering unless you are planning on removing the entire pump)

    Procedure (with timing belt removal)

    Remove the timing belt. See www.myturbodiesel.com/wiki/timing-belt-replacement-mk3-vw-jetta-vw-passat-tdi-removal/ and follow the applicable steps.

    Remove the water pump pulley (3x 6mm allen bolts), (in white text below). You can use an adjustable pipe wrench to counterhold the pulley at the neck, right behind the pulley.

    Remove the intermediate shaft pulley (in yellow below). Counterhold the intermediate shaft pulley with a sprocket holder to remove its 18mm pulley nut. Be careful because the pulley is aluminum. Note the intermediate shaft woodruff key and location.

    You now have access to all the water pump bolts. (8x 10mm bolts). The water pump might be a bit stuck but you can gently tap it with a piece of wood to release it and break the seal. Do not use a metal hammer directly on the water pump or a screwdriver to pry it off. In the below picture, the intermediate shaft seal flange was loosened and had a new seal. From this view, you can see the water pump neck where an adjustable wrench can be used to counterhold the pulley.

    Also note that in the above picture, the previous owner lost the bolt for the lower timing belt cover. There is normally a bolt pushed in from the other side which helps hold the lower timing belt cover, as seen below on another car. The part number is t-head screw 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 because there's no access from the other side to push it through. There are more notes on fixing this in the timing belt writeup. I use gasketmaker stuffed aroud the base of the bolt to lightly stick it in place.

    When putting on the new pump, tighten it's bolts evenly to help the gasket seat properly. Pictured right is a pump with a metal/rubber gasket instead of a paper gasket. You can use the paper gasket but you may want to put a very thin bead of gasket maker on the paper gasket. Put a THIN continuous bead on, most people always smear a large amount of gasket maker on, which then squeezes inside, breaks off, and then gets clogged somewhere. A 2-3mm bead is sufficient. For cars that use water cooled turbos, this can cause them to overheat if their water line gets clogged. This is also why I hate "stop leak" radiator products, just call AAA instead of clogging your radiator. I tried stop leak once and found what look like fried gluten clogging everything. Note - TDI turbos are not water cooled, they are oil cooled only.
    Also note the 3 red circles indicating the recessed bolt holes. If your water pump does not have these recessed areas it will interfere with the intermediate shaft pulley.

    Torque for water pump bolts - 7.4 ft-lbs or 89 inch lbs (ones circled in red to right)
    Torque for 18mm intermediate shaft - sprocket bolt - 33 ft lbs

    Torque for 3x 6mm water pump pulley bolts: 15 ft-lb
    Water pump removal procedure (without removing the timing belt)

    Here is a diagram of what you need to remove.

    Remove the 3 hoses going in and out of the water pump housing. Use a bucket to catch it, I do not recommend reusing the old coolant but you can if it's kept very clean. A pair of remote operated hose clamp pliers (pictured below) is so helpful that I consider it a required tool.

    Remove the alternator and AC compressor and place them off to the side if you feel you need more access. See 1000q: alternator removal for more details. Do not remove the AC compressor hoses or else all the coolant will be released as a gas, just unbolt the compressor and place it to the side.

    Remove the 4 bolts holding the water pump assembly to the engine.


    Replace any lost coolant with fresh coolant. See 1000q: coolant flush for more details.