2005 Kia Sorento Brake Pedal Freeze Up

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.

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.

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.

Check with BBB and look for ASE certified mechanics.

I would go to KIA, this is very unusual and is most likely a manufacturing defect.