Good day all,

I was driving the other night (about 3 days ago) and noticed my brakes feeling different as I had to floor it to come to a stopping point. I immediately came out and checked the brake fluid which was below the minimum mark and topped it up with some brake fluid from a gas station.

Edit: I haven't topped up brake fluid in months so I highly doubt it is leaking.

I've noticed since then when applying brakes I can hear the intake of air by the pedals and when releasing breaks also hear the air escaping sometimes and occasional squeak.

I've spoken to my mechanic and he said I'll need to get a brakes booster and cylinder. I was thinking the brakes would of only need to be bled as I have never had any brake problems before.

Is it certain that I will need a brake booster? Also what other causes can lead to me hearing the air intake and delate like noises with the occasional squeak?

Vehicle: Pajero iO Year: 1996

Thanks in advance.

  • How are your brake pads? Many brake boosters are vacuum actuated and hearing that vacuum isn't necessarily a problem. You might hear it more if the pedal is traveling more because of worn brakes.
    – JPhi1618
    Commented Sep 15, 2017 at 19:18

1 Answer 1


The hissing of air you're hearing is likely due to a torn vacuum booster. This isn't a complete disaster but does mean you are not getting the full effect of power brakes.

The brake fluid being so low is a little mysterious. Do you see any leaks under your car, either near each wheel or near the master cylinder? It's possible the master cylinder is leaking fluid into the vacuum booster, causing it to fail.

You could try a 2nd opinion from another mechanic; it's likely you will get the same answer.

  • Thanks for the answer, the breaks fluid being so low was because I haven't topped it up in months. I really wasn't aware of it being used up (my 2 cents as to why it was low). I haven't been seeing any leaks in the areas you specified. With the assumption it is a torn vacuum booster. Is the price for repair or replacement relatively cheap? Commented Sep 16, 2017 at 0:04
  • @DanielPrince the brake circuit is a closed system (albeit not perfect), you should not need to top up the brake fluid regularly. If brake fluid disappears the circuit has a leak and that needs to get fixed
    – Martin
    Commented Sep 16, 2017 at 18:46

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