99 Caravan, Soft Brake?

HELP !!! I'm at my wits end......

I have a 99 Caravan and recently replaced a rear axle lina and wheel
cylinder and a front calaiper flex line.
I blead the brakes (but only those lines) until I figured all the air was
out.

The brake at this point was good, almost perfect, only a little spongy.
Then, a few days later I lost the brakes again. I assumed that I had
disturbed the steel line going from the flex line to the master cylinder,
but when I checked the fluid level in the resevoir was fine??

Then I was told, or, you have air in your lines, bleed them all, starting
from the farthest point and work your way forward.
So three containers of brake fliud later..................

Still not right.

This is what is happening to my brake right now.
If I push on the peddle it seems fine, but, if I slack off slightly as you
would in slow rolling traffic, and then press again it goes further towards
the floor, slack off again, and it goes more, till after about 3 or 4
pushes, its right to the floor.

I'm still not losing any fluid, so it isn't a leak. Could my master
cylinder be bypassing on one line only?? If it was the front one on the
master the fliud wouldn't be able to leak out?

Any suggestions or comments. PLEASE and Thank-you

David

 

--

If this vehicle has ABS brake System you are going to need a scan tool to
bleed the hydraulic assembly.

Glenn Beasley
Chrysler Tech

 

Does the brake pedal continue to sink while you are sitting at a
light?

Steve B.

 

No ABS on this one Glenn, I'm told now that it may be the check valves.

 

If the brake is up when I initially push on it, and I maintain a constant
pressure on the pedal it generally stays up.

David

 

You say it generally stays up. If it *ever* doesn't stay up and you
aren't loosing fluid then you most likely have failed seals in the
master cylinder. Some times when you bleed a master cylinder you can
damage the seals doing so. Brake fluid absorbs water and water causes
rust in the system. The master cylinder normally has a short range
of travel and keeps the bore within that range of travel shiney and
smooth but the bore outside the range of travel gets rusty and pitted.
Then when you come along to bleed the brakes you run the master
cylinder through its full range of travel and the rubber seals end up
getting damaged by the rough and rusty areas of the cylinder where
they have never been before. Hope you find the problem soon. Let us
know what it turns out to be.

Steve B.

 

Sounds like it's time for an overhaul or new master cylinder, _provided_
everything else is in good working order.

HTH,

Andy.

 

Turns out that I was my own worse enemy. When I changed out one of my brake
lines I used an old bottle of brake fluid that had been sitting on a shelf
in my shed. Apparently it must have somehow gotten contaminated because the
master cylinder on my van had some crud in the resevoir.

The mechanic who changed the cylinders for me said that the seals
deteriorate rapidly when exposed to contaminated fliud. He also told be
that fliud stored in a container with no cover on it will "go off", and
thats even if nothing falls into it, just from the air I guess.

A word to anyone doing brake work, always be sure to use fresh or new fluid.
The stuff you bought last year and used a bit of and then shelved, is
possibly gone bad, and for the sake of a couple of bucks, you could save
yourself some hastle.

I won't do it again, thats for sure.........

David

 

Absolutely. Alcohol-based brake fluids absorb moisture rapidly from the
air.

Yes, this is pretty common knowledge.

Matt