96 Grand Caravan Brake Issue - Feels like air but doesn't seem to

6841 Views 7 Replies 4 Participants Last post by wambus, Jan 22, 2013

sckjhharris

Discussion Starter · Jan 13, 2011

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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sckjhharris

Discussion Starter · #2 · Jan 13, 2011

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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ImperialCrown

· #3 · Jan 13, 2011

With an ABS stop, it is normal for the pedal will drop lower and buzz. If the pedal is already low to begin with, it will be even worse.
I think your problem is at the rear wheel cylinders and the drums will have to come off for a better look. If the fluid that came out of them looked bad, I'm sure that they are internally rusted. You may not see a wheel cylinder leak until you pull the drum.
There should be 2 bolt holes (in the lug nut bolt circle) where you install 2 - 8mm x 1.25 bolts to walk the drum off the hub. Use solvent and lube on the hub and the threads if the drum is rusted on.

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sckjhharris

Discussion Starter · #4 · Jan 13, 2011

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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ImperialCrown

· #5 · Jan 13, 2011

Hot front pad odors may mean that the rears aren't doing their fair share in stopping the vehicle. Have someone step gently on the brake pedal gently while you watch for both rear shoes move outwards, one side at a time. If only the primary shoe moves, block it with a screwdriver to see if the secondary shoe moves. The inside of the drum might show how well the shoe linings are making contact.
Hold-down hardware and self-adjusters can rust up also.
Wheel cylinders can leak and sieze up after some time and they are fairly cheap to replace, if needed.

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sckjhharris

Discussion Starter · #6 · Jan 18, 2011

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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Bob Lincoln

· #7 · Jan 18, 2011

As an aside, you probably could have used a screw extractor and removed those broken bleeder screws, and then bought new ones for only a few dollars each. Much cheaper than replacing the calipers.

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wambus

· #8 · Jan 22, 2013

I just want to say that I have worked on the brakes on many vehicles in my time: 61 Cutlass, 66 Chevelle, 77 200SX, 81 Corolla, 82 Virago, 87 Supra, 88 Hi-Lux, Tacoma, 98 Passat, 89 Grand Voyager, 95 Civic, F350 Super Duty, Schwinn, Huffy and others I cannot remember. I have never had nearly the trouble with the brakes that I have with our 99 Grand Caravan....

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