brakes soft first press with air sound
 

Hey everyone great site! Anyway Im having brake issues with this car. 2006 elantra gls with tcs, abs, 4 wheel disc. Master cylinder is still full of fluid. I havent done any brake work in about a year now the pedal is soft on the first press and fine after that as long as you dont wait more than 5 seconds or so than soft again. with engine off pedal is good and firm. with engine on first press soft and i can hear an air leak noise like a hiss or whistle coming from the master cylinder/brake booster area then no noise and firm on second press and all presses right after. Wait a few seconds and same thing all over again. Anyone have any ideas? thank you in advance!

Probably a bad master cylinder.

thanks for your input! is there a way to test the master cylinder? is replacing it hard to do? i work on cars and such all the time but never did a master cylinder. i would have to bleed the new one somehow and then the rest of the system?

Really no way to test it. It's probably an internal leak. Yes, you bench bleed the master before installing it and then bleed the entire system after it's installed.

A little late but if hiss sound is coming from under dash sounds like a power booster leaking vacuum. Also don't forget to transfer oring between master cyl. And booster. If left out it will cause a vacuum leak and will cause drivability problems. Mil light on with lean codes

I have a 2013 Elantra GLS that had the same problem for 3 years I kept taking it back to belle tire for the brakes. After 3 years and changing out everything with the brakes except the abs system before taking it to a hyundai dealership and found out that the aftermarket calipers didn't "move" the same as the orm calipers. I had them put oem parts on and it completely solved the problem. I was shocked that it was because of the aftermarket parts. Hope this helps.

Of course, we all try to save $$ when purchasing parts. Unfortunately, a lot of parts out there, especially if imported, are Junk. Don't know where the parts replaced came from, but this is a common problem and why those of us in the trade try to stay with OEM parts.

Not all aftermarket parts are questionable, and domestic manufacturers might charge a little more, but quality is much better.