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2g gsx brake issue

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dyablo

15+ Year Contributor
250
2
Jan 22, 2005
Indio, California
got an auto 99gsx that sat for 7years with a blown engine. Got that replaced when went for a drive, noticed the brakes worked but I guess not with full clamping force. Figured it needed new pads and resurfaced rotors. did that on all four corners.

problem still happening so I went and bleed the whole system. tried again still not stopping very well figured maybe a bad master so I replaced that. bench bleed it and rebleed the brakes still having the issue.

thing is at say highway speed I can slam the brakes and they work just fine ABS kicks in. I noticed the issue is at very low speeds like below 20mph I can slam the brakes and they start to work but I run out of pedal travel.

only thing I can think of is a bad booster but at almost 90$ a piece id like to narrow down my options.
 
Check the vac line for the booster isn't leaking. Could be a caliper hanging up alittle. Do you notice any of the wheels getting super hot? Any signs that the old master was leaking into the booster? Mine did that and it killed the booster. You might need to bleed the abs unit as well
 
If a caliper or hose is giving issues, it usually pulls to the side that the problem is on, so it's probably not that. That being said, check anyways. When you say you run out of pedal travel, is it because you hit the floor pan with it or does it stop midwayish like it's supposed to? Is the pedal "feel" correct or is it hard? If it's a hard pedal you probably need a booster. See if there's no paint on the face of the booster under the master. The old one may have leaked fluid inside the booster and killed the diaphragm. If this is the case, you essentially have manual brakes....
 
I checked the hose going to booster and no leaks. Also verified the one way valve was working.

With the car off if I pump the brakes they get hard within a few pumps like any other car. But with car on coming to a say a stop at a parking spot I'm essentially at the very bottom of pedal travel.

It just feels like the brakes don't engage until about 3/4 off the way down at slow speed. Highway they seem fine maybe because there's like -20 vacuum then. As opposed to slow stop sign speed I get maybe -10 ish.
 
It doesn't sound like it's a booster then if it's holding vacuum when the car is off. Vacuum usually doesn't have an effect on pedal travel like that though. If you lose vacuum the pedal usually gets a little higher and harder than a honeymoon skin flute... This is what's stumping me. Did you check if all the bolts for the break pedal box and booster/master were tight? It's just pulling straws, but I'm just trying to think of anything... The last thing I can think of is you may have air trapped in the ABS block. Last ditch effort, I would try to bleed the car per the standard procedure, but use a pressure pot style bleeder with compressed air and blow fluid backwards to the master
 
I have a very similar issue on my talon, subscribed for updates.

I've just dealt with the issue, but would like to get it fixed if it's something easy. I've replaced all 4 rotors and pads and bled the brakes. Helped a bit, but still a problem with the initial brake push (goes down further than it should, but if I pump the pedal first, it has a nice firm feel afterwards).
 
If you both have to pump the pedal to get a firm one, or if the pedal slowly goes down when you're sitting at a stoplight, then it's most likely the master cylinder or an air bound ABS unit if equipped. This is assuming regular bleeding methods were tried and failed and that all four calipers and hoses check out. If it's a master, this symptom happens when there is an internal leak which allows fluid past the seal on the piston inside the master cylinder or an external leak, usually in the rear seal where the master meets the booster. These symptoms will happen irregardless of vacuum level, it will just have a hard pedal if no vacuum is present. Either way, it will slowly go down or require to pump it up. This happens because the piston moves or loses pressure, but it's not actually pushing fluid. It's actually moving THROUGH the fluid or just pushing it out of the master, but not enough through the lines in the case of an external leak. Check if the paint is peeling on the booster under the master. If it is, it's the rear seal blown and it's new master time. If it doesn't appear to have an external leak and the symptoms are the same, and bleeding with a pressure pot doesn't cure it, it's an internal leak in the master and it should be changed. I suppose there are other possibilities, but this is by far the most common situation I have ever run into on any car. Hope this helps...
 
Yeah my pedal does not get hard no matter how many times I press it with the car running. There has to be air still in the system.

I'll try rebleeding it again. Maybe even consider buying that bleeder that forces fluid from up on the master cylinder.

I'll update later, thank you
 
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