Strange Brake Problem

[HGFireHazard]

Hi all. My wife has a 2002 Liberty Sport. I changed her front brakes and pads early last year and also bled the system. She's had no problems between now and then. Today she messaged me this:

"I was at a stop light and all of the sudden I started moving, so I thought maybe I let off of them a little. Light turns green, and I go to the next light. I had to push pretty ******* my peddle to get it to stop. I had it pushed all the way down while at the red light and they started making noises. Like pulsing noises."

She said the brakes worked just fine during normal driving but this symptom only seemed to occur after she had been sitting at a stop light for an extended period of time.

I had her test brake pedal drop after depleting vacuum and the pedal dropped 1-2" when she turned it on which seems normal.

My initial thought is something ABS related but she has no lights on her dash. It seems like an odd thing to happen when the brakes work the rest of the time.

I'm at work so I haven't had a chance to check around the calipers for leaks but considering she said the brakes worked great the rest of the time I doubt there are any.

Any thoughts? Thanks!

 

[dude1116]

Hi all. My wife has a 2002 Liberty Sport. I changed her front brakes and pads early last year and also bled the system. She's had no problems between now and then. Today she messaged me this:

"I was at a stop light and all of the sudden I started moving, so I thought maybe I let off of them a little. Light turns green, and I go to the next light. I had to push pretty ******* my peddle to get it to stop. I had it pushed all the way down while at the red light and they started making noises. Like pulsing noises."

She said the brakes worked just fine during normal driving but this symptom only seemed to occur after she had been sitting at a stop light for an extended period of time.

I had her test brake pedal drop after depleting vacuum and the pedal dropped 1-2" when she turned it on which seems normal.

My initial thought is something ABS related but she has no lights on her dash. It seems like an odd thing to happen when the brakes work the rest of the time.

I'm at work so I haven't had a chance to check around the calipers for leaks but considering she said the brakes worked great the rest of the time I doubt there are any.

Any thoughts? Thanks!

Sounds pretty similar to when one of my brake hoses leaked. Noticed I was losing pressure while stopped, but while driving it SEEMED like I had enough pressure to stop adequately. Sure enough, I parked the Jeep and woke up to a puddle of fluid by my passenger wheel.

It's rare that an '02 has ABS, isn't it?

 

[eradicator006]

Could be the master cylinder leaking internally. If you're not losing any brake fluid then it's probably the master cylinder.

 

[HGFireHazard]

Thanks to both of you for your replies. I'll be sure to check for puddles. Regarding an internal master cylinder leak, is there any way to test for that?

 

[HGFireHazard]

I just wanted to post an update that the issue did appear to be the master cylinder. After not finding any leaks anywhere around the brake system I ordered a replacement and put it in. A relatively simple replacement and all is well again. Thanks!