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2012 Kia Sorento SX, 2003 Honda S2000
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Discussion Starter #1
So yesterday on my way to work I was at a redlight and my Sorento started moving forward. I hadn't released the brake, it just started moving but unsure I pressed the brake pedal in harder. If felt soft but the vehicle stopped again, for a few seconds and then I had to press it in again. By the time I had the brake all the way to the floor it wasn't moving forward anymore but I sure as hell wasn't going to continue to drive it!

I had it towed to Kia (after waiting for a second tow truck because the Kia Roadside lady didn't tell the towing company when I said it was AWD and they would need a flatbed tow truck...) and it's in the shop now so I don't know what the official "cause" was but I'll keep you guys updated.

Be aware that there may be a problem and be safe out there :eek:
 

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2013 Sorento EX V6 AWD
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Sounds like a failed brake booster or some sort of catastrophic leak somewhere in the hydraulic system. Was the master cylinder full of fluid? Did you see anything dripping on the ground (other than water from the A/C drain)?

Best,
 

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2012 Kia Sorento SX, 2003 Honda S2000
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Discussion Starter #3
Fluid was full, didn't see any dripping in the parking lot (except A/C on the opposite/passenger side). I figure it may be a vac leak, but thought that would be detected by some sensor, there were zero warning lights on even when the brake was to the floor.
 

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2013 Sorento EX V6 AWD
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Fluid was full, didn't see any dripping in the parking lot (except A/C on the opposite/passenger side). I figure it may be a vac leak, but thought that would be detected by some sensor, there were zero warning lights on even when the brake was to the floor.
Even if you lost ALL the vacuum to the booster, you should have had *some* pedal. I'll be curious to see what the cause was. Glad everyone is safe.

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2012 Sorento EX AWD CRDI; 2007 Sportage EX CRDi 4WD; 1967 Mercedes 250S; 1958 DKW 3=6
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372 Posts
That is indeed scary and i am glad that you are ok! The funny thing is if you lost vacuum there should be the brake warning light coming on. please keep us posted.
 

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I now drive a 2003 S-10 Had an 03 LX 3.5 Sorento
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Even with out vacuum if the master cylinder was good you would still be able to stop. Bad MC = no stop.
 

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10 Optima LX, 07 Rondo EX, 89 Chevy C1500
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If the pedal drops, its either a bad master cylinder or a leak.

If the booster failed, the pedal would not drop, but instead get very hard. You would still be able to stop, but it would take much more effort because there would be no power assist from the booster. Its the same as if you pumped the brakes without the engine running.
 

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2012 Sorento SX AWD Titanium
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Subscribed. Please let us know. I drive the same vehicle in the same area as you.
 

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I now drive a 2003 S-10 Had an 03 LX 3.5 Sorento
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2,365 Posts
Bad master cyl usually means fluid loss...usually seen running down the firewall or dripping off the booster.
Yes, an externally leaking MC could cause loss of braking. An internal leak, where the fluid is leaking past the piston(s) or plunger would cause poor braking or when bad enough no brakes.
 

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2012 Kia Sorento SX, 2003 Honda S2000
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Discussion Starter #13
Good point about the vac just being used for power-assist...

So apparently it had something to do with the rear brake calipers, parts are on order. They didn't see any leaks so they're thinking it was an internal leak, which doesn't make me feel any more comfortable that it won't happen again :-/
 

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Good point about the vac just being used for power-assist...

So apparently it had something to do with the rear brake calipers, parts are on order. They didn't see any leaks so they're thinking it was an internal leak, which doesn't make me feel any more comfortable that it won't happen again :-/
Rear calipers what? Each caliper should be on a different brake fluid loop. That is done on purpose so that if one brake line leaks you still have some braking from the other circuit. If you had zero braking that would require both circuits to fail simultaneously. That seems really unlikely. I agree with the other posters if all braking failed it would very likely be a master cylinder issue.

Unless you flushed your brake fluid recently and forgot to close the bleeder screw on both rear calipers. Which is hard to imagine anyone would do.
 

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2008 SpectraSX, 2014 Optima LX,2006 Jeep Liberty, Linux Mint Mate
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I agree with phillyguy...
I'm concerned about the dealer's trouble shooting abilities.
If the rear brakes failed totally the front brakes are on a completely different loop/circuit and would not have failed also... I'd be asking about having the master cylinder replaced.
Dave
 

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I agree with phillyguy...
I'm concerned about the dealer's trouble shooting abilities.
If the rear brakes failed totally the front brakes are on a completely different loop/circuit and would not have failed also... I'd be asking about having the master cylinder replaced.
Dave
I do not know specifically how the Sorento's brakes are setup, but usually I have seen the brake circuits setup so that one front and one rear are on the same circuit, usually on opposite sides. I only ever bother to find out when I go to flush the brake fluid since your fluid order will generally have you clear out one circuit followed by the other. But yeah, I hope that the dealership had a really good excuse for how the rear calipers could cause a catastrophic total brake loss.
 

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2013 Sorento EX V6 AWD
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Rear calipers what? Each caliper should be on a different brake fluid loop. That is done on purpose so that if one brake line leaks you still have some braking from the other circuit. If you had zero braking that would require both circuits to fail simultaneously. That seems really unlikely. I agree with the other posters if all braking failed it would very likely be a master cylinder issue.

Unless you flushed your brake fluid recently and forgot to close the bleeder screw on both rear calipers. Which is hard to imagine anyone would do.
Agreed. That explanation makes no sense whatsoever. If it was me, I'd retrieve my vehicle and find another dealer. Inability to diagnose something as simple as the brakes doesn't bode well.

Best,
 

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2012 Kia Sorento SX, 2003 Honda S2000
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Discussion Starter #18
They found evidence of leaking on both rear calipers, however replacing them didn't help so now they've ordered a new master cylinder and they're going to replace that tomorrow...
 

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They found evidence of leaking on both rear calipers, however replacing them didn't help so now they've ordered a new master cylinder and they're going to replace that tomorrow...
Good luck, hope that takes care of the problem. Keep us posted and let us know if that does the trick.
 

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2012 Kia Sorento SX, 2003 Honda S2000
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Discussion Starter #20
New master cylinder did the trick, as an added "bonus" I got the car back w/ a new rock chip in the windshield and a few in the front bumper. :mad:
 
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