Brake Fluid Leak – Kia Rio 2012

[Josue Ramirez]

Hello!

I have a Kia Rio 2012 that leaks break fluid around one of the master cylinder ports.
My question is, is it for sure the master cylinder or could it be the brake line that has a bad flare or the fitting?

I was thinking on getting a bolt with the same size as the fitting and removing the brake line and blocking the port with the bolt to test if there is still a leak, therefore, this would mean the MC is the problem, am I right?

I will post some pictures later today.

Thanks in advance!

Topic

[Andrew Harris]

I don’t think this would work. The flare has a corresponding angled seat inside the master cylinder that makes the seal. If you just put a bolt in it, it would not seal against the seat. I think this would make your test inconclusive either way.

[Josue Ramirez]

Yeah, that’s what I was thinking.

Then should I just replace the MC?

[Josue Ramirez]

Update 3/16

After checking it seems the problem is not the master cylinder, it is the proportioning pressure regulator valve that goes between the MC and the brake line (See Part 58775E – https://kia.7zap.com/en/mes/rio/kmespih12/03:6,/ch/5858511/#58775E)

I have been able to order the valve, is there a specific procedure on changing one of these valves or is it just remove and replace the valve?
Also should I bleed the MC after replacing the valve?

Thanks!

[Andrew Harris]

I would say you just need to remove and replace the valve. If the brakes are spongy after I would perform a traditional 4 wheel brake bleed procedure. If you get air in anywhere it will be at the line.

[Josue Ramirez]

After a long wait, the valve finally arrived!
I was trying to replace it, however the original valve won’t come of, I’m not able to unscrew it.
Is it OK to use some WD40? Also if I applied to much strength could I damage the master cylinder in any way?

thanks!!

[Steve Klein]

You can use WD-40 (or something a bit better like PB-Blaster). Let it soak for 15-30 min. Make sure you are using a ‘flare nut’ wrench. Standard wrench will round the nut. From the drawing above, it looks like you should be able to put a wrench on the valve and then loosen the brake line nut. Then you should be able to remove the valve.

[Josue Ramirez]

The brake line nut comes off easily, the valve is what won’t come off the MC
I’ll try later today, hopefully I can get it out.
Thanks!

[Author]

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