My brake pedal has been making a hissing sound lately that has been getting worse gradually over the past few months. I did a search on the topic and got some useful information about the booster, but my pedal isn't hard, it's going somewhat softer each day. I had major brake work done about a year or so ago - replaced both rear rotors and calipers, and the master cylinder (Midas couldn't figure out what was making the pedal soft...so they just replaced everything, ha!).

So, basically, my question is...even though the pedal is soft, could the problem still be the booster? Would air in the lines create a hissing noise?

Any insights are appreciated - thanks!

 

The hissing is the booster. Replace it.

A soft pedal cannot be caused by a bad booster. It's something hydraulic. If all the big pieces are new, and the system was properly bled (let's assume that it is, since those shops generally know how to do that), it probably needs one or more of the rubber lines.

 

Follow up:

I finally got the money to have the work done ($400 parts and labor). The hissing is gone, the pedal is nice and firm, not "squishy", idle is normal (im guessing it was creating a vacuum leak - it used to jump up and down, and if left idling for a couple minutes the RPMs would drop to 475 and check engine light would come on), and I'm not sure if these are related, but, I'm curious if anyone has any input on this:

At high speeds if I would goose the gas pedal the transmission would slip into a passing gear, but the RPMs would surge up and down a few times before it finally slipped into gear. Now that no longer occurs (so far, haven't had time to test it thoroughly.)
Any thoughts?

One Step Closer to a restored beauty.

 

just for booster replacement???

 

Yeah, I live in the SF Bay Area. Labor around here is between $80-$100/hr. It was $197 in parts, $216 labor.

 

Glad it's fixed.

On the other hand, you can buy the parts yourself for about $100, and replace it in less than 2 hours with nothing but very common hand tools, in your driveway. Sorry to hear it cost you so much.

 

Mental Note: Next time something needs fixing on my car, ask how to do it here first before spending hundreds of dollars at a shop, which should be going towards my new paintjob!

Also, the car _definitely_ has more power and torque now. That explains why even after the engine was just rebuilt I was slightly disappointed with the performance. I'm not now!