Why Brake pedal goes deep?

dongwenxuan · Post by **dongwenxuan** » 09 Sep 2011, 01:38

I got an issue with my 2002 Volvo S60 2.4T, 116,500 miles.

When I made a brake, I need to step the pedal down 30% deep, then the brake start to work, and then I can easily push the pedal down to the floor.

The brake can still work but several mechanics told me to replace the brake master cylinder. So I replaced it yesterday and filled new fluid.

After repair, I feel only a little change on my brake pedal. It still can be push down to the floor (a little bit harder than before). The brake will start working after push it 15% deep (instead of 30%).

I think there might be another problem in my brake system. Anyone met before?

BrendanM · Post by **BrendanM** » 09 Sep 2011, 02:12

I have a similar problem which I am trying to solve today. The pedal travel has got steadily worse over the month. I also suffer from the no brakes at first start in the morning syndrome. I am nearly at the floor now and braking power is not good. I am not using any brake fluid - not topped up in a few years. Pumping brakes makes no difference to the travel. Booster is working becasue if I hold brakes then start the car then the pedal travels further down. It cannot be the master cyclinder seals since surely I would be losing fluid?

Today I will try and flush out all the old fluid since it has been many years since that was done.

dongwenxuan - when you put in your new master cyclinder and bled - did you flush out all the fluid to each wheel or did you just top up?

BrendanM · Post by **BrendanM** » 09 Sep 2011, 04:14

OK some feedback. I sucked out all the old brake fluid from the MC tank. Then filled with new fluid and bled at each wheel until new fluid came out. Kept topping up with new fluid. Order was rear right, rear left, front right, front left. My old fluid was really old & brown. I also seemed to purge some air when bleeding the rear left so that was probably also not helping. Brakes are nice and hard now on the first press. Pedal travel is back to normal.

Post by **Fish stick88** » 09 Sep 2011, 06:19

Thats why i would suggest. If you were having problems before, the air may have been the factor that made it have no pressure, after changing my calipers, i had to do the same, Also.. Did you bleed the lines too when you changed fluid?

Post by **jimmy57** » 09 Sep 2011, 09:50

Low pedal can be caused by many things. If a full bleed of the whole system doesn't resolve the problem then there are some things that I am curious about.
Have the brake calipers been removed and the outboard springs not re-fitted correctly?
Are any of the wheel bearings faulty and loose?

dongwenxuan · Post by **dongwenxuan** » 23 Mar 2012, 13:58

Update. I did a brake fluid flush in dealership and they only charge $75 and applied a 20% off coupon. The pedal won't go down to the floor anymore after this job done. But the brake will only start working after push it 5% deeper compare to a new car. Problem almost resolved.

Post by **vjaneczko** » 23 Mar 2012, 20:50

When they flushed the system, did they re-install the same rotors & pads or replace them? That may be the final piece to the puzzle.

dongwenxuan · Post by **dongwenxuan** » 24 Mar 2012, 12:38

That make sense. The dealer didn't replace the rotors and pads. I'll replace both of them before next brake fluid flush and we will see.

vjaneczko wrote:When they flushed the system, did they re-install the same rotors & pads or replace them? That may be the final piece to the puzzle.