Why do I need to pump my brakes to stop?

[Zexell]

2nd time this happend in a year span.

Got out of school, and I start my car. I come to a stop and all of a sudden, my brake pedal goes all the way in and I need to pump my brakes hard to stop. Even then, I have half the braking power I used to have.

I had my front rotors and pads changed about 6 months ago, and my brake fluid is topped off.

What is causing this problem?

 

[AWDfrank]

I had the same problem but it was because I needed a new brake master cylinder. It was causing a big leak and I would have to pump my brakes a few times to stop. The only difference is that your not low on brake fluid so...

 

[fhudsonjr]

If you can pump them back up to where they feel pretty firm, you probably have air in the lines.

Bleed your master cyl. and then your brake lines.

 

[Zexell]

If I pump them hard, they go back to being firm, only for a sec or two. Then they become soft again.

Does a problem like this happen out of nowhere usually? Both times it happened, they just happened out of the blue.

Thx for all the quick replies.

 

[AWDfrank]

There is definitely air in the lines, I would bleed them first and see where you are from there.

 

[oldman]

Bleed your system, start from furthest to closest relative to the MC, rear passinger -> rear driver -> front passinger -> front driver. Check for leaks prior to bleeding goes without saying.

 

[Defiant]

You're missing the check valve in the booster vacuum line, or it has failed.

The bigger question is why the hell you're driving it.

 

[Zexell]

Thx for the replies. I'll see whats the problem is today.

 

[xveganxcowboyx]

You're missing the check valve in the booster vacuum line, or it has failed.

The bigger question is why the hell you're driving it.

Could you elaborate on the symptoms of this a little bit? I have a minor version of the problems he was complaining about (braking power about 80% unless I give it a good pump first). I had been thinking my master was leaking internally a little bit, but I hadn't even considered the check valve possibility. I don't know much about it.

 

[Defiant]

Cleverly hidden inside the booster vac line is a one-way valve that pulls air from the booster but prevents atmospheric or boosted manifold pressure from entering. If you can blow through both ends of the vac tube, it's failed.

 

[xveganxcowboyx]

Don't think that's my problem, but I'll pull mine and check it. Thanks.

 

[Zexell]

Update:

At first, I went to bleed my rear passenger but realized there was no nipple to bleed. So I went ahead and bled the rear driver side and got a good amount of air out. I thought I fixed it. Fast forward 3 days, then it happened again, and I bled the rear driver side again. Seemed fine, and now a day later, its back to me pumping the brakes again. I obviously have a leak somewhere or something has failed. Can anybody input any suggestions/advice??? Thx.

 

[95blackGsTurbo]

All of your brakes are going to have bleeders. Otherwise you have a serious problem and need to replace the pass. rear brakes. Have someone help you bleed them. Open the bleeder and have them slowly push the pedal down. Then close the bleeder and tell them to let it back up and repeat 3-4 times on every wheel. You can't just bleed one wheel. But it sounds like your problem is in the master cylinder. Sounds like the seal it going bad and it sucking in air. Don't pump the brakes to bleed them. That just induces more air into the system. For all practical purposes I just recommend paying someone to diagnos the problem for you. A few bucks is a lot better than you insurance increase when you rear end someone or hit someone that runs out infront of you when your brakes don't work right away. Shouldn't even be driving the car.

 

[Zexell]

I'm trying to diagnose the problem here. I hate going to mechanics because they lie and dick you over.

 

[95blackGsTurbo]

I have never lied or dicked anyone over. I have cut labor time off of projects that took way less time than the quoted labor. There are lots of reputable shops in Chicago that would be great to take your car to rather than driving around with an intermitant brake problem.

 

[steve]

I dislike going to mechanics for things I can do myself.

They never try to lie or dick me over more than once, if at all. Usually they realize in the first 20 seconds to pay attention to what I'm asking them to do. Since there is no misunderstanding, I don't get surprised later on and think I got taken advantage of.

Zexell, WTH did you think was going on when you went to bleed the caliper and the nipple was gone. You have to fix that problem and fully bleed the brakes before you can drive the car again.

Steve

 

[oldman]

I have never lied or dicked anyone over. I have cut labor time off of projects that took way less time than the quoted labor. There are lots of reputable shops in Chicago that would be great to take your car to rather than driving around with an intermitant brake problem.

That's what they all say!!!

 

[Defiant]

Ever inspect the check valve?