Brake Fluid Overflowing Reservoir
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  1. #1
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    Brake Fluid Overflowing Reservoir

    I just noticed that brake fluid fluid has spilled out of the reservoir, leaking from the cap eventhough it is tightly closed. On unscrewing the yellow cap the fluid is up to the brim of the reservoir. It'a 2003 Passat Variant with 1.8T. Did rear brakes at about 35K, has about 45K now. Fluid was flushed before that. No problems with the pad change or with the brakes that I've noticed. Any ideas??

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  3. #2
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    First of all, clean that fluid off of painted surface area really well. Brake fluid will eat your paint up.

  4. #3
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    Sep 2005
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    Sounds like when your car went in for service the brake fluid was changed then topped off to the fill mark. Then when the brakes were serviced the caliper pistons were compressed in and pushed the fluid back into the brake system. IIR the reservoir is not air tight. Just get a turkey baster or syringe and remove the excess fluid. Clean the engine compartment of the fluid. No telling how long it has been like this but it could cause damage to paint ect.

  5. #4
    3rd Gear
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    I've found that I need to keep it at the "min" mark and not the "max" mark to keep it from spilling out during spirited or auto-x driving. If you look close you'll see a pin hole in the top of the yellow cover where it leaks from.

  6. #5
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    Quote Originally Posted by PGevanthor
    I just noticed that brake fluid fluid has spilled out of the reservoir, leaking from the cap eventhough it is tightly closed. On unscrewing the yellow cap the fluid is up to the brim of the reservoir. It'a 2003 Passat Variant with 1.8T. Did rear brakes at about 35K, has about 45K now. Fluid was flushed before that. No problems with the pad change or with the brakes that I've noticed. Any ideas??
    Wanted to pass on an update.

    I adjusted the fluid level to the bottom of the filler neck again and the next day after a run it was up to the top. Brought it in to what I think is one of the best dealers in the San Diego area and they checked it out and found nothing wrong. "If air were going in via a leak the pedal would be soft but it isn't." The level was adjusted and I took it home yesterday. Today it is overflowing again, leaking onto the top of the reservoir. I will bring it back but I need some ideas and apparently the dealer does also.

    I can't say exactly what they checked. They've never seen anything like it.

    Any brake experts out there? Thanks. Peter

  7. #6
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    Sounds like the reservoir is being pressurized. Bad valve action in the master cylinder?

  8. #7
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    Anyone know the cause of this brake fluid overflow problem? My 02 1.8T AWM has started doing this. Front pads are still original, rears were replaced 6 months ago including a full flush with Valvoline Dot 3/4 syn fluid. Pedal is firm.

    Reservoir level is halfway between min & max, but the neck with the fill cap is full to the top. Why wouldn't the fluid in the neck drain back down into the reservoir?

    I'll be replacing all the pcv valves, fittings & valve cover gaskets this weekend (leaking oil). That would rule out a bad check valve if the brake fluid still leaks afterward.

    Hope it's not the master cylinder or ABS...

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