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    Thread: Brake Master Cylinder Leaking

    1. #1
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      Brake Master Cylinder Leaking

      My daughters 2004 Aveo has 54,000 miles, a leak has started in the brake master cylinder. The leak is actually coming from around the bottom back (nearest the firewall) brake line fitting in the master cylinder. The brake line connects to the master cylinder via a large black fitting of some sort. I do not know what the black fitting is or does?

      Anyway the leak is where this black fitting goes into actual master cylinder body. Anyone else ever has this issue on their Aveo?



    2. #2
      Administrator Daox's Avatar
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      I haven't heard of this issue. Brake lines are pretty standard. Have you tried tightening the fitting?

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      It's possible that it's the Residual pressure valve for the rear brakes.


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      No, I have not tried anything to fix the problem yet. I just took a few moments to find where the leak was but i did not have time to work on it yet. I'm sure that the two lower lines are connected to the MC via two separate Proportioning valves for the rear drum brakes.
      The leak is right around where the back (of the two) Proportioning valve screws into the MC. I'll try to tighten it tonight.
      It just seems weird to me that it could be loose?

    5. #5
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      When I bought my car, and did the first oil change at 500 miles, I found three bellhousing bolts(2 of which hold the rear mount) were sticking out an inch and only had a few threads left before they fell out.

      If it's loose then count it to be poor factory control. But with your mileage it might be a failure of another kind.


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      Update. I replaced the complete MC on Saturday, everything is good now. I was an easy process,
      I had my daughter help with the brake bleeding process. The whole job took maybe an hour or so to do.

      GM only sells the complete MC including the two Proportioning valves. The list price is $192.00 but I have a
      buddy that works at a GM dealership and he got it to me for $120.00

      Before I purchased the new MC I tried to tighten things up but that was a no go. Everything was very tight.

    7. #7
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      good to hear its fixed. after taking it apart and having a new one there to compare, did the problem with the old one appear obvious? like something other members should look out for?


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      I need a master cylinder = 2004 Aveo. Without ABS. Could I get the dealers name. I was quoted $319 here in Canada, for the part.
      Looking to better that.
      Thanks
      Clem

    9. #9
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      Contact ZSPOT at: News - NAIOA


      Car Dealerships in Topeka & Manhattan & Lawrence KS | Used Cars


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      Last edited by Redshiba63; 12-23-2011 at 02:49 PM.

    10. #10
      What's wrong with my car?
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      FYI, I sold the 2004 Aveo this past summer! Wahoo! I'm glad that car is gone.





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