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a4 2.5tdi servicing

Leea4tdi Apr 15, 2009

  1. Leea4tdi

    Leea4tdi Member

    I plan on doing a service to my 2.5 v6 tdi this weekend can anybody give me any tips on how i correctly change the fuel filter?? and how i go about bleeding the system without possibly damaging the injection pump.

    what type of fitting is the sump plug on this engine do i need any special tools for it? many thanks
  2. Leea4tdi

    Leea4tdi Member

  3. The 2.5 is a bit tricky to bleed air out of the fuel.
    Make sure you fill the fuel tank to the brim before doing it.
    Probably best to clamp all 4 hoses by the filter to minimise air getting in the system or the fuel falling back.
    Fill the new filter with fuel.

    Do not open the bleed screw on top of the filter with the engine running or you will introduce air into the fuel.

    Audi have a tool that pulls fuel through the pump via the fuel injector return pipe (leak back) hose.
    I used a 50ml syringe on a piece of hose and another clamp.
    Engine is off
    When you have fitted the new filter remove the two clamps on the fuel feed hoses.
    Clamp one of the injector leak back pipes then remove its end from one bank of injectors
    The other end should still be attached to the pump.
    Insert your syringe into the end of the hose
    Pull syringe plunger up syringe to draw fuel and air into syringe body
    Clamp pipe before removing syringe
    Empty syringe
    Repeat until only fuel is being pulled through then repeat some more.
    It is normal to have a few small bubbles at top of the fuel transparent hose.

    Audi reckon you pull 3 special tools full of fuel through - I reckon this is at least 1.5 -2 litres.
    You can pour this back in the tank.
    Remember to refit the leak back pipe to the injector
    Remove the clamps
    And mop up swill any spills as diesel will eat any non fuel rubber pipes.

    Symptoms of getting this badly wrong are it just won’t start
    Symptoms of getting it a bit wrong are a jerky throttle response were it wasn’t before and a lack of power.

    On a 1.9 tdi this is a doddle on the 2.5 it can be a bit of a ******
    Don’t do it unless you have the tools and skill.
    Worth getting a copy of the Elsa win software (workshop manual) to show you some pictures.
    Don’t do it with a dodgy battery either as even when you have done it right it can still take a bit of cranking to get it going.
  4. Leea4tdi

    Leea4tdi Member

    thanks for the advice :sm4:

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