Rear Brake Question

[rdtebeau]

When riding yesterday, I noticed my rear brake pedal depressed further than normal, pumped it one time and had a full pedal, more than normal. The rear brakes then didn't release very well to the point you could tell that they were applied a bit. Anyway, the question is, any ideas on what could cause this? I did pull the rear caliper and after pumping the brakes I couldn't get the pistons on one side (inboard) to go back into the caliper. I opened the bleed screw and they went right back in with no problem. I flushed the system (it was dirty) and put it all back together. Didn't drive it, but I did pump the brakes, still acts the same sitting still. Also, the brake pads are almost completely gone, but I don't really see why that would cause this issue. Seems like the brake pressure is not releasing. Could the master cylinder cause this or something else? Any help is greatly appreciated.

Thanks,

[bigbear]

When riding yesterday, I noticed my rear brake pedal depressed further than normal, pumped it one time and had a full pedal, more than normal. The rear brakes then didn't release very well to the point you could tell that they were applied a bit. Anyway, the question is, any ideas on what could cause this? I did pull the rear caliper and after pumping the brakes I couldn't get the pistons on one side (inboard) to go back into the caliper. I opened the bleed screw and they went right back in with no problem. I flushed the system (it was dirty) and put it all back together. Didn't drive it, but I did pump the brakes, still acts the same sitting still. Also, the brake pads are almost completely gone, but I don't really see why that would cause this issue. Seems like the brake pressure is not releasing. Could the master cylinder cause this or something else? Any help is greatly appreciated.

Thanks,

A couple of questions for you rdtebeau.

1) Did the brake pedal feal spongy or was it rock solid? From your post I presume after pumping it it once it was solid.

2) How badly worn are your pads. Is the wear all on one side or are both the in-side and outside pads worn approximately the same? One set of pads shot and the others almost new indicates a sticking or binding caliper which you mention in your post.

3) Were you borderline low on fluid? If you were leaning the and on a slope you may have got a small air pocket on the first pump quick release bled majority out then second pump was at a slightly different angle and master cylinder received full charge of fluid. ( admitted long shot but possible)

Now time for the real experts to answer.

[rdtebeau]

1. The pedal felt soft and went away so to speak (like it was bleeding off). The next press gave a solid pedal, but slowly went down, this is when the rear caliper seemed to lock.

2. The pads are worn out, but evenly worn out on both pads.

3. The fluid level was/is okay, not low (was hoping).

I'm thinking maybe the master cylinder is internally leaking by and possibly keeping pressure on after being acitivated and released. Could the ABS unit be causing something like this?

Still wondering?!?!?

Thanks, and sorry for the no name.

Randal Tebeau

[jzeiler]

Randal,

I think you have guessed right. Sounds like it may be time to rebuild/replace the master cylinder. Given the age and properties of brake fluid. Have all the prescribed flushes been performed? That is a BIG factor. My old Suzuki had some pretty bad corrosion in the bore after 22 years of service, but I was able to save it with a rebuild kit.

[rdtebeau]

I've pretty much decided it has to be the master cylinder. I can't find a rebuild kit listed so I'll guess I'll have to go for a new one at $158 and no one has it in stock.....