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Discussion Starter #1
With firm pressure, the brake pedal sinks to floor. The brake pedal is firm when engine is off. I have vacuum bled the system twice now with no difference. The brakes work well stopping the car with no issues.

Any ideas why the brake peal sinks to the floor?

Thanks,

Jim
 

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the brake system is leaking. Since you just bled the fluid, you should check all of the bleeding hoses and tighten them

If you can't sure which one, you can brush some dye on all of hoses, drive the car for a while, and see which hose is leaking out
 

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Discussion Starter #3
No leaks after bleeding the brake system as the brake reservoir does not change level from its full mark. The brake pedal does not move when the engine is off; it only sinks when the engine is on.
 

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The brake pedal won't move when the engine is off because they are vacuum assisted. I would be looking at the master cylinder if the pads and rotors are in good shape.
 

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If you're not leaking fluid externally, then you have a internally leaking master cylinder. Brake pedal should pump right back up.

How much brake pad material do you have on all four corners? Miles on vehicle? original or cut rotors? did you inspect the hoses at each corner for ballooning?

When stopped, don't make it a habit to hold unlimited pressure on the brake pedal. Use only as much pressure as needed to keep the car from moving. With many vehicles, the power assist, if given enough time, is strong enough to make any brake pedal go to the floor. Anxiety panicked drivers tend to keep a death grip on the brake pedal when at redlights/stopsigns.... this type of driver can not be made happy concerning brakes.

If you are confident in your bleeding ability, then its time to seek professional brake 2nd opinion. If not, I would bleed again using a non-fancy DOT3 or OE fluid. Honda/Toyota have excellent DOT3 brake fluids. Honda/Toyota brake fluids have a seal conditioner which is uncommon with store bought brake fluids. Its more of a preventative than a fix but worth a try.

What method of bleeding are you using? Mityvac vacuum? Motive pressure? Two-man?
 

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Discussion Starter #7
Thank you for the responses.

Pads, rotors, caliper slide pins are good. I am going to bring it to the dealer as it should be still under warranty (2014 with 41,000 KM).
 

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Thank you for the responses.

Pads, rotors, caliper slide pins are good. I am going to bring it to the dealer as it should be still under warranty (2014 with 41,000 KM).
I would suspect a bad booster (bad diaphragm). With the engine off, pump the brake pedal a few times, then hold down. Start car. If it drops to the floor when started, most likely a bad booster. Should drop a couple of inches, then hold.
 

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How many miles on the vehicle? +1 on the master cylinder, much more likely than the vacuum booster.

Older friend of mine had to have the MC changed on his 2010 Equinox at 39K miles. Independent shop says not uncommon for sub 50K failure on that vehicle.

That's nuts. Daughters '06 Elantra has 130K+ miles on it, original hydraulics all the way around.
 

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Discussion Starter #10
Dealer checked the brake system and did not find any fault. They said the slow sinking brake pedal at idle is normal for these Sonata (2014) cars.

Should I get a second opinion?

Is everyone finding their brake pedal slowly reaches the floor at idle while applying firm pressure?
 

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What? No it's not normal. Mine doesn't sink at all when I'm stopped.

Of course I have a manual so I don't need to apply my brakes as firmly to keep the car from rolling, at least not on a level surface.


Sent from my iPhone using Tapatalk
 

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It is not normal, mine doesn't sink. As a matter of fact I could grab the bottom of the steering wheel and stand up on my break pedal and I still couldn't get it to the floor.
 

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Dealer checked the brake system and did not find any fault. They said the slow sinking brake pedal at idle is normal for these Sonata (2014) cars.

Should I get a second opinion?

Is everyone finding their brake pedal slowly reaches the floor at idle while applying firm pressure?
Dealer is full of crap. Did you try the test I put up earlier in the thread?
 

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Discussion Starter #14
I would suspect a bad booster (bad diaphragm). With the engine off, pump the brake pedal a few times, then hold down. Start car. If it drops to the floor when started, most likely a bad booster. Should drop a couple of inches, then hold.
RBD,

Yes, I did try this test; the brake pedal slowly sinks to the floor after the engine is started. I even mentioned a possible bad brake booster to the dealer. Mechanic says a bad booster would stiffen the brake pedal.

It looks like I need to go to another dealer.
 

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My 2011 Sonata did the same a few years back and it took a second trip to the dealer with a lot of persistence and a suggestion they look at the master cylinder. They called Hyundai who told them to replace the master cylinder as there had been a few reported problems with same. Bottom line they were just to lazy to check it out the first time.
 

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RBD,

Yes, I did try this test; the brake pedal slowly sinks to the floor after the engine is started. I even mentioned a possible bad brake booster to the dealer. Mechanic says a bad booster would stiffen the brake pedal.

It looks like I need to go to another dealer.
As other have said it sounds like a faulty master cylinder - and if your pedal is sinking to the floor that is a potentail safety hazard and if you bring the word "litigation" if you are involved in an accident you will likely get a far more postive response from the dealer or Hyundai.

Years back had a Taurus SHO that the front rotors warped so badly after 6 months that the car shook hellaciuosly when brakes applied - of course dealer said rotors not a warranty item but in the same breath said it wasn't safe to drive the car. I said I'm not paying for replacement but if I'm an accident I would sue Ford Motor Company - after a quick call to Ford the rotors were replaced - I think I paid .5 hr of labor just to be "reasonable" .
The rotors were just cheaply made.
 

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I have an I30 and it has very slow pedal creep since new if you push the pedal hard without the engine running. I tried another brand new one at the time and it did the same. If you push lightly it wont creep. If you have the engine running it wont creep.
To me it would be one of the primary cups in the master cylinder leaking but Hyundai said it was something in the design of the ABS.
 

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I have an I30 and it has very slow pedal creep since new if you push the pedal hard without the engine running. I tried another brand new one at the time and it did the same. If you push lightly it wont creep. If you have the engine running it wont creep.
To me it would be one of the primary cups in the master cylinder leaking but Hyundai said it was something in the design of the ABS.
Well it seems the OP indicates it happens when engine running.

And is that what Hyundai says (ABS design) about the pedal sinking when the engine is off ?

I would tend to think it's more intrinsic to the way a vacuum assisted braking system functions when it loses it's vacuum.
 

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Discussion Starter #20
Parking brake is normal. How can the parking brake impact the hydraulics and brake pedal? It connects to drum brakes via a cable; does not impact the caliper.
 
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