So I replaced my master cylinder on my 1995 Acura legend and there a hissing sound coming from the brake booster area. Upon more thorough inspection, I found that placing my finger on the bottom side of where the master cylinder and brake booster meet changes the pitch of the hissing, and thus the leak is coming from there. Is it enough to put gasket maker between the 2 parts to solve the issue?

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    Was a gasket there when you removed the old master cylinder? Did you replace the gasket?
    – CharlieRB
    Commented Nov 27, 2017 at 16:39
  • Aparet from the gasket question, have you located the parts properly and are they tightened down correctly?
    – Solar Mike
    Commented Nov 27, 2017 at 16:42
  • Is there a hiss even when the brake is not depressed?
    – GdD
    Commented Nov 27, 2017 at 17:35
  • Yessir, the hissing changes pitch when I press the pedal and let it back up, like its using the vacuum up Commented Nov 27, 2017 at 18:04
  • There was no gasket that I could see. It was caked on with a rust colored material, and I assumed there was no gasket because when I looked on the m/c metal side I saw there was no residue at all! @CharlieRB Commented Nov 27, 2017 at 18:09

2 Answers 2


There is a gasket that sits between the master cylinder and the brake booster. It is a thick rubber gasket that fills the space between the two parts and fits snugly around the master cylinder shaft. part #- 46185-SE0-003

  • Right on man I saw that and I guess I installed it wrong, also glad to know my brake booster isn’t damaged haha Commented Nov 28, 2017 at 14:27

Recently there was leakage detected near brake booster of my honda civic 2005 with a continously hissing sound from engine side. The problem which I was facing was that as soon as I switched OFF engine the brake pedal moved upward and became full hard and brakes failed to work. Removed brake master cylinder and found a broken round rubber seal which sits between brake master cylinder and brake booster. Replaced it and now all is fine.

  • Yeah I was thinking this because on the m/c and brake booster is just 2 flat metal surfaces so I didn’t see anything to prevent vacuum seep between the 2 surfaces.. it would make sense also because the vacuum hose from the engine intake is clamped through and through and he only seepage would be the rubber inside the actual booster, or connection between the m/c and brake booster (which is what it was in this case for us I believe) Commented Nov 14, 2018 at 18:42

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