brakes not working properly

[Dy_]

Hi,

My gf's mit. mirage is playing up abit today. For some reason sometimes the brake pedal goes all the way down when she steps on it...then when she takes her foot off and steps on it again, its fine. Theres also this really bad burning smell coming from near the rear wheels of the car.

I've checked the brake fluid and its still full...so i dont think theres air in the system?

Front brakes have just been changed so they should be sweet. Rears are drums and i have no idea how to check that.

any help would be great! thanks

[aaronng]

Brake master cylinder could have an internal leak. Get it checked by a mechanic.

[ninzee]

yea get it checked asap it happen to my mum a few weeks ago and she didnt get it fixed and yesterday he brakes completely failed had 2 use the hand brake to stop

[Dy_]

what did the mech say was wrong with her car?
Is there any way to find out what may be wrong at home first? I hate bringing a car to the mech and having them tell me bs etc.

[Nepolian]

Get it checked out before something happens!

To check rear drums, pull on the hand brake lightly and see of pedal improves! (yes whilst you're driving).

Never discount air in system tho, re bleed it!

[riruiz_88]

as stated above, its your brake master cylinder. either rebuild the master cylinder or replace it with a new or 2nd hand one. get it fixed right away, if it were me i wouldnt drive it until the problem is fixed.

[Dy_]

mkay after some interrogation, i found out she drive the car 25km's with the hand brake up lol which was the cause of all the smell and brake feeling funny. Since then ive taken it for a drive and things are normal.

might look at getting the shoes replaced though.

[Dy_]

thanks btw!

[riruiz_88]

that still wouldnt cause the pedal to go to the floor. does it happen when you are braking from high speed to come to a complete stop? at stop lights, does it sink to the floor when you have your foot on brake pedal?

[ninzee]

the mech came today and he said something about the brake master cylinder having an internal leak and as a result it created a crack which drained all the fluid out luckly for my mum it was like 5.30 in the morning when she left so there was no1 on the road but that also ment that she didnt notice any fluid on the floor, wat you could do to see if its leaking is put a peice of cardboard under your car one night and the next morning see if its leaking and how much but i would recommend buying a new cylinder as you wouldnt know how much life the 2nd hand one has left, dont go all tight ass on the sh1t that keeps you safe

[riruiz_88]

you can also tell if its leaking when the paint on the brake booster starts to peel off as well as other surrounding areas that are painted. or simply just have a feel around for fluid

[JohnL]

you can also tell if its leaking when the paint on the brake booster starts to peel off as well as other surrounding areas that are painted. or simply just have a feel around for fluid

An internal leak occurs when hydraulic pressure escapes past one of the master cylinder piston seals, and the fluid that escapes with it returns to the reseviour, and thus isn't apparent outside the MC (so no peeling paint etc). In this case the fluid level in the reseviour remains normal because there is no external leak.

The typical symptom of an internal fluid leak is though the brakes work more or less normally, the pedal sinks slowly to the floor when holding the car stationary with the brake. The pedal will typically 'pump up', but then start falling again.

It's dangerous because it means the seals are marginal (at best...), and this problem may suddenly become a lot worse in which case the brakes won't work properly when you need them to.

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The OPs problem seems to only have occured during the handbrake incident? If so then it was probably caused by the handbrake having been left on, which could have overheated the rear brakes and thus caused the fluid to boil (possible water contamination of the fluid lowering it's boiling point, but it may have just become so hot it would have boiled whether contaminated or not?).

If the brake fluid hasn't been changed for a couple of years (or you don't know when it was last changed...) then it would be a good thing to change it now.