brake issue

Friends has a van that has a random brake issue. Twice in about a three month period after the van set for about eight hours or more the first five to ten pumps of the brakes were soft like air in the system then the brakes are solid.

He ask me to help him check it out. Based on the description I thought maybe the fwd axle was loose causing piston to retract while parking. Didn't find any leaks or brake pad issues. When checking fluid the brake master cylinder reservoir cap was loose I felt. The fluid was black. We changed the fluid and the brake pedal is now solid hard, a change from a decent pedal feel.

Could this be the cause or is the master going bad?

I'm assuming vacuum boost?
How old is the vehicle?
I'd suspect rubber brake hoses for the occasional spongy feel. There are three hoses, one on each front wheel, one at the rear. Can you give us some more info on the vehicle?

Its a 2009 Hyundai version of the kia sedona. I think it has 70k miles.. It has four rubber hoses.

By using solid and rock feeling I mean the brakes are good/great.

Probably a bad master cylinder, crawl under the dash and see if the pushrod is leaking fluid.

Kenny_McCormic wrote: Probably a bad master cylinder, crawl under the dash and see if the pushrod is leaking fluid.

If the problem comes back replace the M/C even if you don't see any evidence of a leak.

Kenny_McCormic wrote: Probably a bad master cylinder, crawl under the dash and see if the pushrod is leaking fluid.

It was leak free!

HappyAndy wrote:

Kenny_McCormic wrote: Probably a bad master cylinder, crawl under the dash and see if the pushrod is leaking fluid.

If the problem comes back replace the M/C even if you don't see any evidence of a leak.

That what I suggested.

Which brand to trust Raybestos or Centric?

fluid shouldn't be "black" after only 4 yrs / 70k miles. did someone put the wrong fluid in it somewhere along the line?

Pbw wrote: Its a 2009 Hyundai version of the kia sedona. I think it has 70k miles.. It has four rubber hoses. By using solid and rock feeling I mean the brakes are good/great.

I have NO IDEA why, but I read that thinking it was a Ford van. That's why I thought one rear rubber hose (again, assumed a full-size van at that). It appears my brain is firing on no more than 5 cylinders, and not even the right firing order. I'm going to bow out

Pbw wrote: Its a 2009 Hyundai version of the kia sedona. I think it has 70k miles.. It has four rubber hoses. By using solid and rock feeling I mean the brakes are good/great.

You answered your own question. If the brakes are now "good/great" it was the old fluid that had moisture and air causing the problem.

AngryCorvair wrote: fluid shouldn't be "black" after only 4 yrs / 70k miles. did someone put the wrong fluid in it somewhere along the line?

I agree (Yeah, I know. I said I was going to bow out, but I'm not giving in to this Alzheimers.)
Usually black fluid comes from the breakdown of rubber components. At that kind of low mileage, I'd suspect the MC. Then again, if the seals in the MC are breaking down already, the calipers and rubber hoses are suspect as well.

It happened again, I'm pretty sure the master cylinder is leaking internally. This time braking hard while on a rough road the ABS engaged and the pedal went soft.

The owners said they can recreate it by braking extremely hard until ABS engages and the pedal goes soft.

Wish I'd seen this earlier, I had a similar problem from a leaky MC that was hard to diagnose because it was filling up the brake booster.

Keep me posted on what you find out. I have a Kia Sedona with 91,000 miles on it. We haven't had that issue, but certainly something I'd be curious to know about.

GameboyRMH wrote: Wish I'd seen this earlier, I had a similar problem from a leaky MC that was hard to diagnose because it was filling up the brake booster.

Yup. The fluid will cause the rubber diaphragm to deteriorate. When the rubber flexes the right way you lose vacuum boost. Any time a MC is removed you should always check the inside of the booster.

On our first Lemons car, when we were on the brakes the engine would smoke. We found the master was leaking into the booster, then pulled into the motor and burnt. It gets old dumping 27$ pints of race brake fluid into the reservoir. Check the vacuum line to the intake for brake fluid.

In reply to clownkiller:

And if you have a leak into the booster, its new booster time too.

It all got replaced.

Replaced the master seems fixed. Pedal does not go soft after abs engages.

The rear of the old master had some seriously black fluid.

Bought a cardone brake master bleed tool this thing makes it simple. www.youtube.com/watch?v=IHLi4tyFcJo