2007 Kia Picanto Sticky brakes

Tiny
HAWX
  • MEMBER
  • 2007 KIA PICANTO
  • 1.1L
  • 4 CYL
  • 2WD
  • MANUAL
  • 91,000 MILES
Hi! I have a Kia Picanto 2007 and have been encountering sticking front brakes for months now. Changed both front brake calipers, flex hose, master cylinder but still issue persist. Especially through traffic where a lot of braking is involved. Brake pedal will get hard and feel the car tends to slow down. Brought it to many car mechs but still issue re-surface every week. No ABS installed. Master cylinder (has 4 port) was changed last week and issue is even worse and occurring almost every day! Can you please shed some light on the issue?
Do you
have the same problem?
Yes
No
Friday, August 15th, 2014 AT 12:48 AM

15 Replies

Tiny
CARADIODOC
  • EXPERT
Next time this happens, loosen a steel line at the master cylinder to see if the brakes release. If they do, try it again by loosening the nuts that hold the master cylinder to the power booster. If that works, something is holding the master cylinder partially applied. Some booster push rods are adjustable and could be too long, but if this started with the original booster, it's more likely the brake light switch is misadjusted and is holding the pedal down a little.
Was this
answer
helpful?
Yes
No
+3
Friday, August 15th, 2014 AT 1:06 AM
Tiny
HAWX
  • MEMBER
Hi. Thank you for the quick reply. Will definitely note it down. Also, I have noticed that the brake pedal have no free play. Could that also be causing my brake to stick?
Was this
answer
helpful?
Yes
No
+3
Friday, August 15th, 2014 AT 1:29 AM
Tiny
CARADIODOC
  • EXPERT
Yup. If the brake pedal is held down just a little, the lip seals in the master cylinder will block the fluid return ports. The trapped brake fluid will keep the brakes applied just a little, and that will cause them to get warm. That causes the fluid to expand, and since it can't flow back into the reservoir, the increased pressure applies the brakes even harder, ... And more heat results which expands the fluid even more.

The same thing can happen if the brake fluid was contaminated with a petroleum product. If you suspect that might have happened, we'll have to discuss the remedy before you put any new parts on the vehicle. Engine oil, transmission fluid, and power steering fluid will destroy all the rubber parts in the brake hydraulic system. That becomes a real expensive repair.
Was this
answer
helpful?
Yes
No
+1
Friday, August 15th, 2014 AT 2:58 AM
Tiny
HAWX
  • MEMBER
I have just confirmed that the free play for the brake pedal is about 0.15 inch! It has free play but barely. If that is the issue then how come sometimes only the driver side wheel stick more often?

For the contamination, I do not think so as lately is seems only the driver side brakes are sticking. But if that was the case, how will one determine contamination?
Was this
answer
helpful?
Yes
No
+3
Friday, August 15th, 2014 AT 4:03 AM
Tiny
CARADIODOC
  • EXPERT
The fastest way to identify contaminated brake fluid is to look at the rubber bladder seal under the reservoir cap. If that is blown up and mushy, so are all the other rubber parts that contact the brake fluid, in particular, the lip seals in the master cylinder.

You didn't say if the brakes release when you loosen a steel line at the master cylinder.
Was this
answer
helpful?
Yes
No
+3
Friday, August 15th, 2014 AT 8:05 PM
Tiny
HAWX
  • MEMBER
I have check the seals in the master cylinder and looks fine.

The car have not yet experienced the sticky brake issue so I will have to advise after it has happened as it happens randomly.
Was this
answer
helpful?
Yes
No
+2
Saturday, August 16th, 2014 AT 3:41 AM
Tiny
HAWX
  • MEMBER
I took it for a test drive doing a lot of braking and my left brakes started sticking this time. So I did as you said and loosen the steel line for the left brakes and the pedal was smooth again. What could be the cause?

Also, I noticed when bleeding my front brakes that my car engine will tend to lower down or shut off completely when the brake pedal is pressed all the way to the floor.
Was this
answer
helpful?
Yes
No
+4
Saturday, August 16th, 2014 AT 7:30 AM
Tiny
CARADIODOC
  • EXPERT
Now you're starting to add some new problems to the story. The issue is whether the stuck brake will release, and it did, so the list of suspects is real short. There's no need to bleed the system. That is done to get air out of the fluid. Air compresses and will prevent the brakes from applying. That's the opposite of the problem you're having, so forget about bleeding.

The power booster is run on engine vacuum. The farther you push the pedal, the more stored vacuum in the booster will be exhausted, and the incoming air will have to be pulled out by the engine. That mimics a vacuum leak, and vacuum leaks result in increased engine speed without a corresponding increase in power. You have too much air to go with the fuel the Engine Computer is commanding. In response to the increased engine speed, the computer will try to lower it back to the desired idle speed. It lowers idle speed by reducing the amount of air bypassing the throttle blade, AND by cutting back on the amount of fuel. It is programmed to know how much fuel to provide based on the amount of air coming in, but it doesn't know about that extra air coming from the power booster. Cutting back on fuel is what is causing the low idle speed. That is a secondary symptom that's not related to the sticking brake problem.

I cringed when I read your comment about pushing the brake pedal to the floor. That must never ever be done unless the master cylinder is less than about a year old. Crud and corrosion build up in the lower halves of the two bores where the pistons don't normally travel. When you push the pedal to the floor, either during bleeding or when you're surprised by a ruptured hose, running the pistons past half way runs the lip seals over that corrosion and can rip them. At that point you'll have internal leakage where the brake fluid can sneak past the seals and it won't get pushed down to the wheels to apply the brakes. Often the symptoms don't show up for two or three days. The symptoms are the pedal will go too far down to the floor or it will slowly sink down when you're holding steady pressure on it, as in when sitting at a stop light. The only fix for that is a rebuilt master cylinder. Mechanics pretend there's a block of wood under the pedal and never go more than half way down with the pedal unless it's a new master cylinder that won't have any corrosion in it. Pedal-bleeding with a helper who pushes the pedal all the way down is a common mistake inexperienced beginning mechanics often make.

The suspects now are anything that is blocking the trapped brake fluid from getting past the point where you loosened the steel line and returning into the reservoir. There's only one thing that can be, and that's those lip seals on the two pistons. Now we have to determine why those seals aren't moving back far enough to expose the return ports. There's two possibilities. The brake fluid is contaminated with a petroleum product or something is holding the brake pedal down a little.

A single drop of power steering fluid, transmission fluid, axle grease, or engine oil is all it takes to become a disaster. Experienced brake specialists even wash their hands before handling brake parts to avoid getting fingerprint grease in the fluid. About a dozen cars were damaged at a national chain store about 20 years ago when the mechanic wiped out a funnel used previously for engine oil, and used it to fill a "bleeder ball" from a five-gallon pail of new fluid. The residue in the funnel was all it took to do all that damage.

Every year I did a demonstration for my students to show what happens when the fluid is contaminated. I had two beakers with fresh, new brake fluid, and I put a new rubber seal in each one. In one beaker I added one drop of power steering fluid, then we watched them for a week. After that week, the seal in the contaminated fluid had grown by about 25 percent and was real soft and mushy. When that happens in the master cylinder, the seals grow past the fluid return ports and blocks them. The result is self-applying brakes that lock up, then release when they cool down.

Here's the secret though. The ONLY proper fix is to drain the old fluid, remove every part that has rubber in it that contacts the fluid, flush and dry all the steel lines, then install the new parts and new fluid. If any rubber part is not replaced, the contamination will leach out of it and recontaminate the new fluid and all the new parts. That means new calipers on the front, new wheel cylinders or calipers on the rear, three or four new rubber flex hoses, master cylinder and the bladder seal under the cap, and the combination valve with its rubber o-rings. Trucks and minivans usually also have a height-sensing proportioning valve in the rear that has rubber o-rings, and if the vehicle has anti-lock brakes, the hydraulic controller is full of seals and o-rings. Those are expensive enough that the vehicle could be considered a total loss.

Lets hope there's a mechanical issue holding the brake pedal down too far. There's two possibilities again for that. Some power boosters have an adjustable push rod, and on the replacement booster it could be adjusted out too far. That could be the case with a replacement booster, but not the original one unless someone monkeyed with it. The second suspect is the brake light switch is misadjusted and the button is holding the pedal down. It only takes 1/8" to cause this problem. To identify if this is a mechanical problem, the next time the brakes lock up, loosen the nuts that hold the master cylinder to the power booster, and pull the master cylinder away from the booster by about 1/8". If the brakes release, start by looking at the brake light switch.
Was this
answer
helpful?
Yes
No
+2
Saturday, August 16th, 2014 AT 9:35 PM
Tiny
HAWX
  • MEMBER
The info you provided are really starting to shed light on the subject. I borrowed an OBD car diag tool from a friend in hopping to find some info stored on the car's computer and it did! Two sensor specifically. The error code listed is a below:

P0031 Powertrain HO2S Heater Control Circuit Low (Bank 1 Sensor 1)
P0134 Powertrain O2 Sensor Circuit No activity Detected (Bank 1 Sensor 1)

That could explain the improper air/fuel mixture as you stated.

After closely examining the brake booster under the hood, I noticed that the lower round frame of the booster is bended inwards! Could that be causing excess air in the system? I am unable to confirm if that is the original booster as it is a second hand car.
Was this
answer
helpful?
Yes
No
+2
Sunday, August 17th, 2014 AT 1:26 AM
Tiny
CARADIODOC
  • EXPERT
I forgot that you replaced the master cylinder. If that was a newly-rebuilt unit, no damage was done by pushing the brake pedal to the floor.

There's no air in the brake system. Get the brakes to drag again, then stop the engine and loosen the master cylinder's mounting nuts a little. If that lets the brakes release, look at the booster's push rod and the brake light switch. One of those is holding the master cylinder from fully releasing.
Was this
answer
helpful?
Yes
No
+2
Sunday, August 17th, 2014 AT 2:00 AM
Tiny
HAWX
  • MEMBER
Yes the master is brand new. Yesterday I examined the brake switch position and decided to adjust it so to see if the switch is not the one causing the issue. After I did that and took it for a drive, I did notice a difference in car performance. The car was more smooth and responded nicely when accelerating. But I will monitor a few more days and see if the issue arise.
Was this
answer
helpful?
Yes
No
+2
Monday, August 18th, 2014 AT 10:44 AM
Tiny
HAWX
  • MEMBER
The brake switch adjustment worked only a day and now back to square one. I got the brakes to stick again, jacked the car up and turn both front wheels by hand (to check on the stiffness of turning the wheels). I then loosen the screws which holds the master cylinder to the booster and sure enough, the brakes did release. The tires where once more free to turn, but not as easily as I wanted them to spin. So the booster pushrod and/or brake booster is the culprit?
Was this
answer
helpful?
Yes
No
+1
Tuesday, August 19th, 2014 AT 3:29 AM
Tiny
CARADIODOC
  • EXPERT
Check the push rod to see if the end is threaded and adjustable. If it is, shorten it by about 1/16".
Was this
answer
helpful?
Yes
No
+2
Tuesday, August 19th, 2014 AT 10:47 PM
Tiny
HAWX
  • MEMBER
Yes the end is adjustable. I have adjusted a little and will monitor a few more days.
Was this
answer
helpful?
Yes
No
+2
Saturday, August 23rd, 2014 AT 1:31 AM
Tiny
HAWX
  • MEMBER
Hi. Issue has been finally resolved. The adjustment did help but not as much as I wanted. So I decided to replace the booster, and it was smooth once more. I haven't had an issue since. Many thanks for your assistance! I will definitely recommend your site & support to my friends.
Was this
answer
helpful?
Yes
No
+4
Sunday, September 7th, 2014 AT 5:53 AM

Please login or register to post a reply.

Recommended Guides