Brake fluid question - Kia Minivan content

The vehicle in question is 2010 Kia Sedona with approx 68,000 miles on it. The brakes were getting low (pedal and pad material) and any high speed stops would produce vibration from the fronts (most likely uneven deposits on rotors).

To fix the issues I replaced all four rotors and pads this past weekend. The supplies were all from NAPA, their premium rotors and adaptive on pads (yeah, yeah, all marketing hype but they provide a nice pedal feel and braking on my Elantra).

The problem is that the pedal is low and doesn't have a solid feel. The van stops smoothly and with enough force to engage the ABS on dry pavement if desired.

My initial thought is the master cylinder is starting to fail, based on my experience. But most of my experience with this type of issue has been on older vehicles without ABS, so I wanted to get some feedback before replacing any parts.

It still has the original brake fluid in it, and the brake system has never been opened up beyond removing the cap on the master. Fluid level is at the full mark, and I have never added any (dealer has done all oil changes, so I don't know if they topped it off).

Could the lack of solid pedal and low pedal be caused by the old fluid?

Thanks, Joe

Flush the brake fluid, it makes a big difference.

Also FWIW on those vans its been my experience it took a bit of time for the brake pads to wear in, it will firm up a bit more with use. My mom had an 06 and I went through this same thing.

Most higher mileage Kia vans that come through work have horrible pedal feel. Flush the fluid.

Agreed, flush the system, regardless of the mileage, it is 5 years old. you can even skimp with cheapest parts store brand, it's still light years ahead of old fluid.

As far as actually stopping, I do a series of medium hard stops on dry pavement from 40-ish to 15.... let them cool with a decent no brake drive for a few minutes and then a few panic stops and drive home and let cool. Seems to work the best for me to fix brakes that don't stop.

Thanks for the feedback.

Whats the easiest way to flush the system?

I'm familiar with bleeding brakes, but figure there are probably a few tricks to flushing the system that would make it easier.

Thanks.

Empty the reservoir as much as possible, fill with new fluid and bleed the brakes. I personally just gravity bleed the farthest caliper until I have to fill the reservoir back up to a point more then the original old fluid level. The other 3 won't take anywhere as long or require hardly any fluid. Just top off when done.

idk how the park brake mechanism works on that vehicle, but I've seen some cars where it was incorporated into the rear calipers (as opposed to an additional drum brake setup inside the rotor hat). Occasionally they'll get stuck, and the result is some air gap between the pistons and the back of the brake pad. Every time you step on the peddle it will take up the slack, but when you let off they retract back into the bore again instead of staying put.

In reply to belteshazzar:

This has the separate drum setup in the rotor hat, so that shouldn't affect it.

The rest of the hardware including slide pins and pistons are free.

If it wasn't that the system hasn't been opened I'd think it had air in it based on the feel. As far as I know its never been opened, so that's why I'm thinking fluid or master.

Fluid.

I flushed the fluid on my 2009 Mazda3 back in I think 2013(only 4 years old at that point) and with 35k on it... I was astounded at the difference it made. No other changes at all.

Now I bleed my brakes 1-2 times per year.

E36 M3ty fluid. Follow Ranger50's advice re fluid and gravity bleeding.

Flush. I've had a 2nd gen Sedona since 2007 (first an '07 and now a '10). Brake pedal feel was never great even when new. But it gets really spongy with age. Fluid flush will help a lot.

Revisiting this since the problem remains and progressively got worse.

The van was recently in to the dealer where their diagnosis was that the issues were all due to the aftermarket pads and a torn boot on the caliper. They were willing to replace the pads, rotors and front calipers (aftermarket) for the low, low price of $1,000.

I said "No Thank you", but did buy the Kia pads and replaced the pads, rotors (napa premium), and inspected the calipers (all 4 wheels). Only one caliper had a torn boot on the piston, but pushed back smoothly without any binding. There was plenty of pad material left, but the front rotors were heavily discolored due to heat, but the rears did not show the discoloration that the fronts did.

The brakes don't feel any different after the recent pad/rotor change (Kia pads) under normal use, and unless you literally stomp on the pedal, the ABS does not engage. ABS won't engage if you apply pressure gradually, no matter how hard you press. An interesting observation is that the brake pedal improves for a while after the ABS engages, but gradually returns to the soft pedal.

I have also noticed during hard braking the front end dives a lot, almost as if there is little to no rear braking. According to tech that I went on the test drive with today, the mileage and strut wear are the cause of the severe nose dive.

I have an appointment Thursday morning, where they plan to reinspect the brake system and the tech wants me to stick around so he can show me what he finds. I will try to be polite.

TL:DR start here:

Summary: The pedal is firm when the engine isn't running and the ignition is off. When engine is running the pedal has poor feel and braking performance is poor and seems heavily bias toward fronts. Fluid was changed at the dealer last year, and didn't improve brake feel and its gotten worse. Recent installation of new pads, rotors did not improve braking or brake feel, except for short periods of time after ABS activates.

Now for the question, does anyone know if there is a way to test the electronic brake distribution system on a 2010 Sedona?

Since the ABS module also regulates the brake force distribution, and since the pedal and brake feel improves for a period of time after engaging ABS, I think the issue may be related to the EBD system defaulting to a heaving bias towards the front brakes.

Does this vehicle have a height sensor on the rear suspension, which would tell the brake controller when the rear is loaded versus empty? If so, make sure that thing is doing its thing. If it always says "rear is empty", then your brakes will always be biased toward the front.

I don't think there is a ride height sensor. What little bit of info I could find leads me to think it uses the stability control sensors and abs wheel speed sensors to determine proper bias.

There is a bleeding procedure using a scantool to cycle the ABS for your car. Most likely you'll need a factory scantool, so it might be worth it to pay the dealer to do it properly.

In reply to NEALSMO:

I had them do the fluid change, so I would expect they followed the proper procedure from the FSM.

Part of the mystery with the poor performance is that the fluid change done by the dealer showed no measurable improvement.