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2002 Chevy Impala Master cylinder extrenal leak

Tiny
STANSBERRYJ
  • MEMBER
  • 2002 CHEVROLET IMPALA
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 102,555 MILES
I have a leak between the maste cylinder and I think its called the booster iits a big round black thing where the master cylinder connects too. No brakes light on brakes are fine. Started pouring out fluid when I changed my fornt brakes. NO fluid lost really. IM puzzled.
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Tuesday, September 28th, 2010 AT 6:43 PM

11 Replies

Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
How much of a leak is it? If it's very small (just enough to wet the area) than that is normal. If it is quiet a bit (noticable loss in the resevoir) and continues than the master cylinder may need replaced.
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Monday, March 8th, 2021 AT 10:56 AM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
It's just spilling out the top of the reservoir because it was too full when you pushed the pistons back in. You probably should have opened the bleeder and pushed it out there but it shouldn't be a problem. Just make sure the cap is tight and rinse the fluid off.
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Monday, March 8th, 2021 AT 10:56 AM
Tiny
STANSBERRYJ
  • MEMBER
  • 5 POSTS
Ithe resvior is basically full like I could fit an ounce but when I changed my brake fluid started leaking on top of the tranny. Then onto the ground. I had my friend dad look and there fuild coming out the end facing the driver seat. But its a small amount>
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Monday, March 8th, 2021 AT 10:56 AM
Tiny
STANSBERRYJ
  • MEMBER
  • 5 POSTS
Resvior was wet though just between the master cylinder and the booster I beilve its called thank you for your help
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Monday, March 8th, 2021 AT 10:56 AM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
It's a little rare to happen that way but if your sure it's coming out of the back, then you have a bad master cylinder.
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Monday, March 8th, 2021 AT 10:56 AM
Tiny
STANSBERRYJ
  • MEMBER
  • 5 POSTS
Whats the cheapest way to repair this. I mean my brakes feel fine for now. No lights are on
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Monday, March 8th, 2021 AT 10:56 AM
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
I would keep an eye on it for a day or two, if it continues to leak than the seal is bad and the master cylinder will need replaced, but as I said it is normal for a small amount (very small) to sometimes come out between the booster and master cylinder when replacing these brakes, moreso on vehicles with ABS which yours has.
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Monday, March 8th, 2021 AT 10:56 AM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
I do not agree that it is normal for a master cylinder to leak at all.

The ONLY way to repair it is to replace the master cylinder. I don't recommend using anything remanufactured if you don't want any more problems.
Make sure you bench bleed it before installing it.
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Monday, March 8th, 2021 AT 10:56 AM
Tiny
STANSBERRYJ
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  • 5 POSTS
Alright ill keep my eye on it thank you for yours help
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Monday, March 8th, 2021 AT 10:56 AM
Tiny
BLUELIGHTNIN6
  • MECHANIC
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Wrenchtech perhaps I am using the wrong term. Maybe SEEPAGE is better? But yes, a leak (seepage, small wet spot) does occur in between the booster and master cylinder sometimes during brake replacement and it is not a cause for alarm. An all out leak, fluid dripping type of leak, is indeed a sign of a failed seal.
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Monday, March 8th, 2021 AT 10:56 AM
Tiny
WRENCHTECH
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If there was a big enough stain for him to see, then I would expect a brake loss in the near future.
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Monday, March 8th, 2021 AT 10:56 AM

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