Mechanics

BRAKE PEDAL FREEZE UP

2005 Kia Sorento

Brakes problem
2005 Kia Sorento 6 cyl Four Wheel Drive Automatic 100000 miles

When it is very cold, below 10 degrees, I cannot push my brake pedal down to get the car out of park. As the car warms up the pedal works better. Braking improves but is still weak until the engine compartment fully warms up.

Big O says I need a new " sensor" for $500. KIA says they must actually " see" the problem to diagnose it. Local mechanic talked to a brake expert who said to run a can of super expensive fuel system cleaner through the engine to clear the vacuum line to the brakes.

Master cylinder was replaced a few months ago after total failure of hydraulic brake system. Brake system has been bled twice since to attempt to fix problem. Brake expert said to replace a particular O ring in the master cylinder if the engine cleaner doesn't work. He said it was probably not the vacuum booster.

I need a fourth opinion.

Thanks,
Bill
Avatar
Wcamero
February 20, 2010.



Hi wcamero,

Thank you foe the donation.

First thing is to forget the expensive fuel cleaner. How is it going to clear clogged vacumn hoses? If any vacumn lines are clogged, the only way to clear them is to go directly to them. Fuel cleaner would only be burnt in the engine and gets thrown out of the exhaust.

When the engine is stopped, the brake booster should have some residual vacumn inside it and this would allow the brake pedal to have assist for a few strokes even when the engine is not running.

Seems the vacumn leaked when the vehicle is parked and you would have to test if it is the master cylinder to booster seal that is leaking or the booster itself is bad. The other item to check would be the one way valve inside the brake booster hose.

Check if the vacumn booster hose from engine to brake booster has collapsed. Some would collapse over time and this would not allow the engine vacumn to assist the booster.

Even when there is no power assist available, you should be able to depress the brake pedal though it requires much more force. I am a little puzzeled over this.

If the problem had occurred only after the replacemetn of the master cylinder, you should recheck the installation and the seal in between. You need not disconnect the brake pipes.

Remove the holding bolts and gently pull out the master cylinder from its seat with gentle bending of the brake pipes and you should be able to check the seal or O ring condition.

Prior to replacement of the master cylinder, brake fluid could have leaked into the booster and this would cause heavier than normal braking strength required. Use a small hose to try to drain out the fluids if any is present.

KHLow2008
Feb 20, 2010.
Thanks for the reply. But why does it only happen during very cold weather? The pedal does not move at all. It is rock solid?

Tiny
Wcamero
Feb 20, 2010.
That is why I am puzzled.

If it is rock solid, then most probably the master cylinder is frozen due to the weather.

I have no experience with such freezing conditions so I will seek the help of other technicians to see if they can shed some light on it.

Hold on while I check it out.

KHLow2008
Feb 20, 2010.
Brake fluid is not going to freeze, so I think you have some water in the brake fluid or getting into booster.

You may also have a leak in system allowing air in.

But the " rock hard" pedal would have to be water freezing, especially since it works after warming up.

Another possibility is that water is getting to linkage and freezing it, or you have a vacuum hose leaking and water is getting in there.

When this happens, is idle normal?

I would start by flushing entire system and refill with new fluid from unopened container.

Having lived in Alaska for two years, I can tell you brake fluid will not freeze at -60F : ).

I would also avoid any mechanic that says a fuel cleaner will clear a vacuum line.

Mmprince4000
Feb 21, 2010.
Thanks for all the info. The pedal is frozen before and after the car is started. The idle seems normal after starting.

This morning it was 12 degrees F and the pedal went down enough to allow me to shift into gear. The brake pedal seemed stiff and the brakes would slow me down but would not engage tightly until the car warmed up. I let it sit a while after they worked well and the fade returned. It went away again after warming up.

Where do I find a mechanic that is trustworthy in the Boulder, CO area?

Tiny
Wcamero
Feb 22, 2010.
Check with BBB and look for ASE certified mechanics.

Mmprince4000
Feb 23, 2010.
I also live in the Boulder area and am having the same problem with my 2005 Kia Sorento. I have not had the problem of not being able to get the car in gear, but while driving I cannot engage the brakes. I have to pump them and push really hard in order to get them back. It started about 2 winters ago (have not had the problem the entire time I have had the vehicle). I have less than 50,000 miles on my vehicle. Everyone I talk to about this, says it is very odd. I am about ready to go to Kia and have them look at it, hoepfully it will be under warranty.

Tiny
Hydeehi
Jan 12, 2011.
I would go to KIA, this is very unusual and is most likely a manufacturing defect.

Mmprince4000
Feb 11, 2011.