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Thread: LT46 Brake Issues

  1. #1
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    LT46 Brake Issues

    Hi All,

    I bought an 2006 LT46 a while ago, brakes worked perfectly fine. It has been stood for a year or so while it's been converted and the pedal has gone spongey.

    Done so far;
    - New Master Cylinder.
    - Fluid refresh & bled twice.

    When the van is off, the brake pedal is solid. With the van running the pedal goes spongey. Can pump it up but with constant firm pressure it will slowly drop to the floor but only while running. I've tried disconnecting the vacuum line to the servo, restarted the engine and the pedal is rock solid. Also no leaks in the system as the fluid level in the reservoir is constant and have been pumping the pedal repeatedly. Anyone had this happen or have any idea what could be causing it? Only thing I can think of is the ABS module must be leaking through a return valve but only when under the added pressure of the servo. Any idea that don't involve an ABS module replacement or rebuild before I go down that track?

    Cheers,
    Josh.

  2. #2
    Administrator Keithuk's Avatar
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    First posts normally go in introductions else you could get a free fix and we never see you again!!!

    What did you use to bleed the system manually or a pressure bleeder?

    Check you have vacuum at the brake servo. Pump the pedal a few times the exhaust any vacuum.

    Hold your foot on the brake pedal and start the engine the pedal should go down slightly as the vacuum it applied.

    You need to get your motor scanned (preferably with VAG-COM\VCDS) for any error codes logged in the ecu and post them, that will save a lot of guessing and check systems out.
    2010 Golf GTD (170) CBBB, 5 Door, Shadow Blue (P6/D5Q), Transmission Code: KXZ, Flat Tyre Indicator, Basic Protection Pack + VCDS.


  3. #3
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    I'll be around for a while, don't worry about that!!

    I've done both manual and pressure bleeding. Have vacuum at the servo, have since checked all the slide pins on the calipers to see if any were seized and they are all fine. I've checked the operation of the load valve and that seems to work fine. Just waiting for an adaptor plug to convert the round plug to the usual OBD plug then I can give things a scan. As soon as I can I will post any codes.
    2006 LT46 Ambulance 2.8 TDI V6

  4. #4
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    Just to update on this for anyone having a similar issue, I've taken the van in for diagnostics earlier this week and apparently it is the ABS valve block causing the issue with a dodgy outlet valve/valve seat allowing pressure to seep into the return side of the brake system which according to the guy doing the diagnostics, he sees a lot on LT & Sprinter vans.
    2006 LT46 Ambulance 2.8 TDI V6

  5. #5
    Administrator Keithuk's Avatar
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    As I've said:

    You need to get your motor scanned (preferably with VAG-COM\VCDS) for any error codes logged in the ecu and post them, that will save a lot of guessing and check systems out.
    2010 Golf GTD (170) CBBB, 5 Door, Shadow Blue (P6/D5Q), Transmission Code: KXZ, Flat Tyre Indicator, Basic Protection Pack + VCDS.


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