Hello,

I'm having a brake issue. The first symptom was the brake pedal fading at stop lights, but it was firm during braking. This very quickly worsened (next time out) into the brake pedal fading all the time until I run out of fluid, the brake light comes on and I have rear brakes only.

If I put more fluid in, the fading but working brakes return and the brake light actually turns off. I cannot find any leak. I'm thinking with these symptoms and the way the brakes start working again after adding fluid that it must be the master cylinder?... and it's probably leaking behind the master cylinder into the brake booster where I can't see? Am I right that the brakes probably wouldn't start working again after adding more fluid if the leak were any further into the system?

Also, my 2004 Cavalier has ABS and the bracket for the "ABS box" (I don't know what to call it... lol) is mounted on top of the master cylinder mount. Is this going to make it really hard to remove and replace my master cylinder?

Thanks MUCH for any advice!

Have you pulled the drums in the back to see if the wheel cylinders are leaking? I'd pull the calipers off and check them too. However, for how bad it sounds it seems like you're on the money with a master cylinder. It very well could be leaking into the booster. If you can't find anything wrong at the wheels I'd do the master cylinder next. If that doesn't fix it, the abs modules themselves can and have gone bad in the past. As for actually swapping it out, I'm not sure because I've never done one personally so I'll let someone else comment. I don't think it'll be too hard.



"In Oldskool we trust"

I kind of ruled out the rear brakes because they seem to be all I have left after all the fluid leaks out. I pulled the front wheels and couldn't find any leak from the calipers, flexible lines (what I was hoping it was) or the metal brake lines. I didn't see any drips under the car or in the wheels at all after pumping the brakes some... and the fluid goes quick. It kinda' has to be the master cylinder. Just being insecure I guess... lol. I never had to replace one before. Thanks very much for the reply.

Hardest part is standing on your head to get the linkage unhooked at the pedal. Good luck and let us know how it turns out!



"In Oldskool we trust"

Aww.... That wasn't it.

I got a rebuilt master cylinder cheap on Amazon. Even for the cheap price, I got a decent bench bleeding kit and new O-rings and mounting pins for the old reservoir. That was cool, because I was worried about not having those things.

The ABS module had enough give to move out of the way when I loosened the master cylinder bolts and freed it's bracket. I didn't have to remove any linkage at the brake pedal. You scared me with that! That would probably be if you wanted to remove the booster.

I brought the old master cylinder inside to switch over the reservoir and bench bleed the new one. That's when I knew I screwed up. The back of the old master cylinder where I thought it was probably leaking from was bone dry. I should have loosened it up and looked back there before I ordered the new one, but I was too lazy.

After I was done. I was testing my brakes and shooting out more fluid with the engine running. Then, I pulled back the car and found a sizable brake fluid puddle somewhere between the rear wheels, towards the center of the car. I don't know how I missed the leak last time. Maybe it wasn't as bad, or I didn't start the car and shoot as much fluid out. I'm trying to work in an apartment parking lot and there were some wet leaves on the ground too. Brake fluid can look a lot like water. But, I actually saw it drip now and I know where it's coming from. Looks like I need some brake line in the rear. Really, none of them look great and they should all be replaced. I wish I had a better place to work and ramps or jack stands. I have squat.... and there's a ton of snow out there now. There's supposed to be 4 days in the 40s coming. Hopefully, that will melt some snow and I can at least get the leaky line replaced. Looks like I'll need to invest in some sort of 1-man brake bleeding toll too... and hope the bleeder screws don't just snap off of my 10-year old wheel cylinders.

Sux. Good luck man, I know how it is to not have tools and be in an apartment like that. Are you in the northeast? Sounds like the same weather we're getting here.



"In Oldskool we trust"

I'm in Lakewood, Ohio. Just west of Cleveland. We usually don't get snow piling up until just before Christmas. Well... it really is just before Christmas... lol. I should have gotten this taken care of more quickly. At least I know what I'm dealing with. Don't know how I missed that leak before, but it's a gusher now. Thanks for the moral support!

The trick to getting brake bleeders loose (or any bolt for that matter) is to smack it with a hammer BEFORE trying to turn it. A couple good blows breaks the bond created by corrosion. You might have to replace the bleeder, but that's much cheaper than a caliper or cylinder. Also if your master cylinder is leaking you should see a wet spot behind it without even loosening anything.