Brake Fluid Leaks on 2017 Kia Optima - Kia Forum

 
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post #1 of 6 (permalink) Old 06-07-2019, 07:48 AM Thread Starter
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Brake Fluid Leaks on 2017 Kia Optima

I bought a 2017 Kia Optima LX (2.4L) in April at the local used car dealer. Right off the bat, I suspected that the brake pedal was kinda soft / mushy. I didn't think much of it at the time though. In May, the parking brake light turns on and I brought it to a mechanic, who topped off the brake fluid. He said he looked under the car, and the brake lines look OK and couldn't find any leaks. This was about 1-month ago.

Just a few days ago, the same thing happens again. My parking brake light turns on again, and I checked the brake fluid level and it is low again. I looked around the master cylinder myself and it looks super clean. After some online research, I suspected that it might be either the master cylinder or the vacuum booster:
- Master Cylinder: I checked the brake pedal and after two pumps, the brake pedal stays at the same place with minimal pressure. Application of hard pressure was able to get the pedal to the floor. Constant pressure does not move the pedal to the floor though
- Vacuum Booster: I pumped the pedal with the engine turns off. Then turned-on the engine. Maintaining the same pressure, the brake pedal slides about 1-2 inch down upon turning the engine on.

Based on the above tests, the issues don't seem to be on the master cylinder or vacuum booster.

I'm thinking I might bleed the brake, but I'm not sure if that will do anything - especially if there is a leak... Any suggestions?

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post #2 of 6 (permalink) Old 06-07-2019, 11:10 AM
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Originally Posted by Eka Linwood View Post
I bought a 2017 Kia Optima LX (2.4L) in April at the local used car dealer. Right off the bat, I suspected that the brake pedal was kinda soft / mushy. I didn't think much of it at the time though. In May, the parking brake light turns on and I brought it to a mechanic, who topped off the brake fluid. He said he looked under the car, and the brake lines look OK and couldn't find any leaks. This was about 1-month ago.

Just a few days ago, the same thing happens again. My parking brake light turns on again, and I checked the brake fluid level and it is low again. I looked around the master cylinder myself and it looks super clean. After some online research, I suspected that it might be either the master cylinder or the vacuum booster:
- Master Cylinder: I checked the brake pedal and after two pumps, the brake pedal stays at the same place with minimal pressure. Application of hard pressure was able to get the pedal to the floor. Constant pressure does not move the pedal to the floor though
- Vacuum Booster: I pumped the pedal with the engine turns off. Then turned-on the engine. Maintaining the same pressure, the brake pedal slides about 1-2 inch down upon turning the engine on.

Based on the above tests, the issues don't seem to be on the master cylinder or vacuum booster.

I'm thinking I might bleed the brake, but I'm not sure if that will do anything - especially if there is a leak... Any suggestions?
Bleeding the brakes will not solve the problem of fluid loss, you will need to find a better qualified mechanic to track down the fluid leak, which might be from the master cylinder into the cabin, not necessarily at the wheels.

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post #3 of 6 (permalink) Old 06-08-2019, 07:26 AM
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Bleeding the brakes will allow you to get rid of any fouled fluid and give you an opportunity to inspect the hoses and bleeder valves down by the calipers where things are more likely to break. Sounds like a good next step.
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post #4 of 6 (permalink) Old 06-08-2019, 07:50 AM
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Bleeding the brakes will allow you to get rid of any fouled fluid and give you an opportunity to inspect the hoses and bleeder valves down by the calipers where things are more likely to break. Sounds like a good next step.
Leaks at the master cylinder are just as likely as they are at the wheels, and the fresh brake fluid wouldn't have a different viscosity, so don't understand the reasoning that it would aid in tracking down the leak.

Although its quite possible for a leak to occur at a break in a metal line of flex hose, the more common area of leakage is worn master cylinder or brake cylinder seals.

A high percentage of people do not change the brake fluid when due, and being hygroscopic it leads to the moisture causing corrosion in the master and brake cylinders, which wears the seals prematurely, and makes that the more common area of leakage.

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post #5 of 6 (permalink) Old 06-08-2019, 01:09 PM
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Your vehicle is only 2 years old. You don't mention how many miles. Any chance its still under warranty even though your the 2nd owner? Perhaps call a local dealership and ask them?
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post #6 of 6 (permalink) Old 06-08-2019, 08:33 PM
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Seems likely that with the wheels off to bleed and change the fluid, tinkering around and exerting pressure on the lines, OP's more likely to observe the problem happening, wherever it ends up being. Suggesting he check the undercarriage since that's where all the rocks and road debris are flying. Beats taking it back to another mechanic for an issue they'll have trouble reproducing. Besides, the car's 2 years old and he's due for a fluid change anyway.
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