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Discussion Starter · #1 ·
I have a 1996 Grand Caravan ES with anti-lock brakes. I hadn't opened the system for quite a while and the last time I did I fully bled it and the brakes felt great. The other day, the brakes just started to feel a bit spongy on the way to work. On the way home they felt a LOT spongier. I had to pump the brakes to get them to stop the van, but they did work once pumped. It feels like there is air in my system, but I didn't open it and it came out of nowhere. I have inspected the whole system and can't find any fluid coming out anywhere so I'm not sure where any air could get in if there is any.

I did have my brake light come on going around a corner a couple of time a few weeks back. I assumed the fluid was low as the light turned off after I completed turning the corner each time. Anyway, when I got home I went to top off the resevoir and it was already full. The little bit of fluid I added just filled up the filler neck. I didn't see the light come on again after that, though.

Anyway, fast forward back to the issue. I bled out the wheel cylinders and got some nasty fluid out, but not any air. The fluid coming out of them now is nice and clean, though. I went to bleed the front calipers and broke off both bleeder screws (they were frozen in). The broke off in the sealed position, though, so I bled them at the brake lines going into the calipers. The pedal was still spongy, but it still stopped the van so I kept using it.

I ordered new calipers and did some research. A bad brake booster would make for hard applies. That isn't my issue, mine are really soft. A bad master cylinder with an internal leak should have pedal fade. I don't have any. You have to pump the brakes to get the brakes to apply decent, but once they're on, they're on. They don't fade towards the floor as I sit at a traffic light. I kept an eye on my fluid level and it wasn't going down at all (no external leaks I can find to let fluid out or air in). I was hoping there was somehow air in the top of the calipers although I have no clue how it would've got in.

Anyway, the new calipers arrived today and I put them in and bled the front brakes. The van feels the same as before. I'm kind of scratching my head on what to do next. I needed new calipers anyway since the bleeder screws broke off, but I also have something that allowed the system to suddenly feel like it full of air when I can't find any while bleeding (and I was thorough). Any experience anyone has had that could explain this mystery to me?
 

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Discussion Starter · #2 ·
I found another post that said something about bleeding out the anti-lock system either at a dealership with the scan tool or just making the anti-locks kick in several times to force the air out of that part of the system. Since I live in a place it snowed the last two days, it wasn't hard to exercise my anti-locks. I found some bad roads and anti-locked away. Then I went and found some clean roads and tried to do some stops. I still have a lot of pedal travel but I don't have to pump the system. The van will come to a complete stop with one press of the pedal, albeit a long press (not all the way to the floor, though).

One thing I noticed was that when the anti-locks kick in the pedal starts going towards the floor and pretty much bottoms out at the end. How exactly does the anti-lock system work. Why does the pedal fade when it kicks in? I can feel the vibration in the pedal and the pedal starts stroking towards the floor.

In one post, somebody said he was having brake issues so he disconnected the anti-lock pump and his van has been working great now for over a year (with no anti-locks now).

I am trying to understand the interplay between anti lock and pedal fade. I didn't mention in my first post, but I first noticed this "air in the system" feeling while driving on slick roads. It's been snowy/icy here for the past couple of months and I never noticed any brake issues before the cold. Maybe there is some interplay between the anti-locks and my issue. I can usually feel and hear pulsing in the brake system when the anti-locks kick on. Could the anti-locks contribute to this "air in the system" feeling, though, without hearing/feeling the vibration that goes along with the anti-locks being active?

Both front brakes are working. When I got home my van wreaked of hot brake pads and there was heat coming off of both sides.
 

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Discussion Starter · #4 ·
Thanks for the feedback. You do bring up a great point. The one place I didn't check for a leak was inside the drums. I did play with the back of the wheel cylinders to bleed them out, but not with the part where they should be sealing internal to the drums. They are only a few years old, but maybe there is an issue with them all the same. I did not, however, notice any fluid loss in the resevoir. I'll pull both drums and look around for any evidence of leaking.

THANKS!!
 

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Discussion Starter · #6 ·
You were right. I pulled the rear drums and the right rear had a leaky wheel cylinder. There was no fluid coming out of the bottom of the drum (yet), but everything inside the drum had a nice coating of brake fluid going. Redid the rear brakes and things are great now. Thanks!
 
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